Iron Containing MetalâOrganic Frameworks - ACS Publications

Review www.acsami.org

Iron Containing Metal−Organic Frameworks: Structure, Synthesis, and Applications in Environmental Remediation Xiaocheng Liu,† Yaoyu Zhou,*,† Jiachao Zhang,† Lin Tang,‡ Lin Luo,† and Guangming Zeng‡ †

College of Resources and Environment, Hunan Agricultural University, Changsha 410128, China College of Environmental Science and Engineering, Hunan University, Changsha 410082, China

‡

ABSTRACT: Metal−organic frameworks (MOFs) with Fe content are gradually developing into an independent branch in environmental remediation, requiring economical, effective, low-toxicity strategies to the complete procedure. In this review, recent advancements in the structure, synthesis, and environmental application focusing on the mechanism are presented. The unique structure of novel design proposed specific characteristics of different iron-containing MOFs with potential innovation. Synthesis of typical MILs, NH2-MILs and MILs based materials reveal the basis and defect of the current method, indicating the optimal means for the actual requirements. The adsorption of various contamination with multiple interaction as well as the catalytic degradation over radicals or electron−hole pairs are reviewed. This review implied considerable prospects of ironcontaining MOFs in the field of environment and a more comprehensive cognition into the challenges and potential improvement. KEYWORDS: iron-containing MOFs, structure design, synthesis, adsorption, catalytic degradation

1. INTRODUCTION Metal−organic frameworks (MOFs) have attracted substantial attention for decades as classic ordered porous solids.1 With the development of chemical synthesis gradually reaching an adjustable level, numerous applications of functionalized materials were extended in different areas.2 For the chemical versatility, nanoscale iron-based MOFs with engineered cores and surfaces can be the carriers for imaging and drug delivery in the domain of biomedicine.1,3,4 Overcoming the energy shortage with efficient and inexpensive method, MOFs were applied to lithium-ion batteries for the lithium storage,5 energy generation for the carbon dioxide reduction,6 and fuel cell for a lower energy barrier to the reduction or evolution of oxygen as well as water oxidation.6−8 Moreover, large quantities of reactions in organic synthesis could improved by iron-based MOFs (e.g., olefin hydrogenation,9 cycloaddition reactions,10 and one-pot oxidative synthesis11). Nonetheless, the most common use of MOFs appear in the environmental remediation, such as selective ion trapping,12 gas adsorption,13 catalytic degradation of organic compounds,13,14 reducing the toxicity of metal ions, and enhancement of membrane-based separations.15 Among numerous MOFs applied for environmental remediation, iron-containing MOFs have attracted extensive interest because of a combination of semiconductor properties and Fenton process.16,17 Several paper reported that the ironbased (cobalt-based) nitrogen-doped catalyst shows a superior stability to noble metal (e.g., Pt) for the single active site.18,19 We found that the structure of iron containing MOFs highly © 2017 American Chemical Society

attributed to the catalytic activity and stability. Conventional MILs have been applicated wildly under mild pH and ambient temperature, indicating an easier secondary treatment in the actual environmental remediation.20−22 Besides, the presence of some ligands might contribute to the extra loss of oxidant, and nanocages drived from Fe−Co Prussian blue analogues (PBAs) were proposed as an improvement hollow structure.23 Several attractive methods for the changeable Fe site have been showing distinctive performance in the enhancement of stability,24 chemisorption,25,26 and catalytic activity.27 Because of the introduction of magnetism, the core−shell structure exhibted a superiority to the adsorption and a potential application at industrial level.28−30 Most of the present synthesis methods for the iron-containing MOFs goes beyond the solvothermal synthesis, whereas the assistance of microwave and ultrasonication will obviously accelerate the heating time. Meanwhile, additional regents (e.g., H2PdCl4, HAuCl4·4H2O, and H2PtCl6·6H2O) and composites (e.g., graphite-based materials and Fe3O4) were adopted for the improvement of classical MILs. We also present the synthesis of hybrid magnetic materials,17 and the metalloligands as a replacement of organic linker.31 The current environmental problems mainly caused by inorganic ions, organic matters and toxic gas, which could efficiently remove though various iron containing MOFs. One Received: February 21, 2017 Accepted: May 26, 2017 Published: May 26, 2017 20255

DOI: 10.1021/acsami.7b02563 ACS Appl. Mater. Interfaces 2017, 9, 20255−20275

Review

ACS Applied Materials & Interfaces of vital fields in removal method is adsorption, apart from high specific surface area (SSA) and additional electrostatic interactions, MOFs with unsaturated Fe possessed excellent adsorption properties evaluated by DFT.32 Another domain of environmental remediation is catalytic degradation, including but not limited to photocatalysis and heterogenerous catalysis with extra oxidant (e.g., H 2 O 2 , persulfate (PS), and peroxymonosulfate (PMS)). In addition, the reduction of toxic heavy metals accompanying with the investigation on the simultaneous degradation were also discussed.33−36 Furthermore, the degradation mechanism has been deeply expounded based on the photogenerated electron−hole pairs, hydroxyl radicals (•OH) and sulfate radicals (SO4•−). As illustrated in Figure 1, the publications on iron-containing MOFs have gradually increase with brilliant developments, and

environmental restoration with assistance of MIL-100(Fe).37 As illustrated in Table 1 and Table 2, the typical iron-containing MOFs have coordinated 1D, ultrathin 2D, and interleaved 3D structure (Figure 2A). 2.1. Hollow, 1D Microrod, and Ultrathin 2D Structure. Several iron-containing MOFs with hollow structure have been designed for the potential application for lithium ion batteries and catalyzing organic reactions while few of them were adopted for the environmental remediation.38,39 To our best knowledge, FexCo3−xO4 nanocages have been adopted for the degradation of BPA with a distinctive hollow structure derived from PBA FeyCo1−y[Co(CN)6]0.67·nH2O.23 The increase of iron doping amount contributed to a more uniform nanostructure of FexCo3−xO4 nanocages as illustrated in Figure 2B, and the Fe0.8Co2.2O4 nanocages have a higher SSA of ∼62 m2 g−1 than conventional spinel-type catalysts. This mixed transitionmetal oxides (MTMOs) conquer the defect of traditional iron containing MOFs by eliminating CN− which may prefer to consume the oxidant. Although there is seldom 1D iron containing MOFs, the 1D pore channel system was used to construct 3D morphology MIL-53(Fe).16 A novel concept of 1D microrod was also proposed by Zhang et al. for the MIL-53(Fe), and 1D microrod was used as a basic of MIL53(Fe) hybrid magnetic composites (MHMCs) for a decoration with Fe3O4.17 Moreover, a 2D structure of Febpydc with well-defined diffraction peaks were designed by Li et al. as a replacement of heterogeneous catalyst for Fenton process.40 The comparison of Figure 3A and B clearly exhibit a smaller size of 2D Fe-bpydc (thickness of 100−500 nm) than the 1D microrod (lengths of several tens of micrometers and diameters of 4−10 μm). 2.2. Coordinated with Metalloligands. Iron sites of ironcontaining MOFs were frequently distorted, whereas various metal atoms existed in the connected ligand, compared to the commonly organic ligands (Figure 3C). Me3Sn cations were adopted by Etaiw et al. to construct [(Me3Sn)4Fe(CN)6] (C18H36N6FeSn4, M.W. = 867.13) with K4[Fe(CN)6].27 The result of IR-spectra confirmed the formation Me3 SnN 2 connecting units with structure of the trigonal bipyramid (TBPY-5) due to the asymmetric νSn−C change the band of νFe−C from 592 to 553 cm−1. Compared to the poor stability of organotin-polymer, the stability of Fe−Co PBAs was enhanced by the random [Co(CN)6]3− vacancies in the crystal structure keeping the charge balance.24 Meanwhile, the coexistence of Fe and Co would generate quantities of singlet oxygen on the water coordinated iron sites with a cubic lattice structure (Figure 4a). With the analogous structure to the cubic structure, pillared-layer-type MOFs were fabricated by the pz (pyrazine) pillar ligands and 2D FeIIMII (M= Ni, Pd and Pt) layers (Figure 4b). The spin state of FeII sites in Fe(pz)[MII(CN)4] are reversibly changeable with the uptake of various guest molecules, and the Fe(pz)[Pt(CN)4(X)p] (X = Cl−, Br−) indicated a chemisorptive uptake of Cl2.25 In the latest reseach, the distinctive spin state transitions of Fe(II) sites have been applied for the reversible CO scavenging based on Fe3[(Fe4Cl)3(BTTri)8]2·18CH3OH (Fe-BTTri).26 Specifically, the release of CO converts low-spin Fe(II) centers to a high-spin ground state, enabling the recyclability of the novel material (Figure 4c). Recently, Schiff base ligands were introduced for the synthesis of iron-containing MOFs with FeIII-salen complexes and d10 metals (Zn, Cd).41 The [N2O2] pocket of L4− anion (H4L = 1,2-cyclohexanediamino-N,N′-bis(3-methyl-5-carboxy-

Figure 1. Trends in the number of publications on MOFs with Fe content and timeline (inset) showing the remarkable breakthrough of iron containing MOFs for the environmental degradation in last five years (data obtained from Web of Science on January 12, 2017).

we attempted to comprehensively review the present research for the environmental remediation from three perspectives based on the iron containing MOFs. The first section proposed several novel design of structure with considerable capacity demonstrating an insight into the future development. The second section deals with the basis of current synthesis method with general guidelines. The features and performances of the iron-containing MOFs in environmental remediation were showing in the third section, which confirmed the reliability with data and mechanism explanation. In addition, the stability issue of iron0containing MOFs (e.g., self-decomposition, dissolution, reaction with medium) was also presented in the fourth section. Finally, we summarize the mentioned issues on the iron-containing MOFs and provide outlooks with comparison as possible.

2. DESIGN OF NOVEL STRUCTURE Generally, a small size leading to SSA denotes excellent performance in adsorption and catalysis; however, an extremely small size tends to aggregate to lower SSA, definitely caused by a lower surface energy.2 Especially for the photocatalysis based on typical MOFs, a well-defined crystallinity would likely benefit for degradation efficiency.34 Nevertheless, high porosity is one of the most important characteristics of MOFs for a wide application; some nonporous MOFs were also used for the 20256


Review

ACS Applied Materials & Interfaces Table 1. List of the Iron-Containing MOFs Applied in the Contaminant Degradation compd

dimensionality

MIL-88B(Fe) MIL-88B(Fe), MIL-100(Fe), NH2-MIL-101(Fe) and NH2-MIL-88B(Fe) MIL-53(Fe)-Graphene MIL-88B (Fe) and NH2−MIL-88B (Fe) NH2-MIL-88B(Fe) and NH2-MIL-101(Fe) MIL-53(Fe) M@MIL-100(Fe) (M = Au, Pd, Pt) Fe2O3@Zn-MOF-74 MIL-53(Fe) hybrid magnetic composites Fe-bpydc Fe(BDC) (DMF,F) FeII@MIL-100(Fe) Fe3O4/MIL-88B(Fe) (nanosheet-based microsphere) [(Me3Sn)4Fe(CN)6] Fe−Co PBAs Pd@MIL-100(Fe) [Zn2(Fe-L)2(μ2-O)-(H2O)2]·4DMF·4H2O [Cd2(Fe-L)2(μ2-O)(H2O)2]·2DMF·H2O [BaNa(FeL)2(μ2−OH)(H2O)]·DMF·2H2O MIL-53(Fe) NH2-MIL-101(Fe) MIL-100(Fe) and MIL-68(Fe) Fe3O4@MIL-100(Fe) (core shell) MIL-88B(Fe) (microcapsules) MIL-101(Fe), MIL-100(Fe), MIL-53(Fe) and MIL-88B(Fe) Fe3O4@MIL-101(Fe) (core shell) MIL-53(Fe) magnetic iron/carbon nanorod FexCo3−xO4 nanocages CoFe2O4

3D 3D 3D 3D 3D 3D 3D 3D 1D 2D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D

additional oxidant

contaminants

ref

H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 H2O2 persulfate persulfate persulfate persulfate peroxymonosulfate peroxymonosulfate

dye dye alcohol Cr(VI) Cr(VI) Cr(VI) and dye Cr(VI) and dye U(VI) dye phenol phenol dye dye dye dye PPCPs chlorophenol chlorophenol chlorophenol dye toluene benzene dye tetramethyl benzidine (TMB) dye dye dye dye bisphenol phenol

84 98 51 33 34 96 89 97 17 40 20, 81 21 54 27 23 44 41 41 31 86 83 85 28, 42 55 93 43 92 95 23 94

Table 2. List of the Iron-Containing MOFs Applied in the Contaminant Adsorption compd

dimensionality

contaminants

species

ref

MIL-100(Fe) MIL-88A(Fe) MOF-235(Fe) MIL-100(Fe) MIL-100(Fe)/graphene oxide MIL-100(Fe) CP/MIL100(Fe) and MIL100(Fe) MIL-53(Fe) MIL-100(Fe) MIL-100(Fe)/graphite oxide MIL-100(Fe) MIL-88A(Fe) and MIL-88B(Fe) Fe(pz)[MII(CN)4] (pz = pyrazine; M = Ni, Pd and Pt) MIL-88B(Fe) and NH2-MIL-88B(Fe) Fe3[(Fe4Cl)3(BTTri)8]2·18CH3OH Fe-BTC

3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D 3D

hydrochloride fluoride dye dye dye organoarsenic sulfur-containing compounds sulfur-containing compounds acetic acid ammonia NH3, H2S and NO2 NO Cl2 CO CO methanol and acetone

inorganics inorganics organics organics organics organics organics organics organics toxic gas toxic gas toxic gas toxic gas toxic gas toxic gas toxic gas

59 58 64 62, 65 52 67 37 60 61 53 72 73 25 50 74 69

2.3. Combined 3D Structures. The core−shell structure is one of the most common combination structure of iron oxide core and MOF shell. As illustrated in Figure 6a, Fe3O4 nanoparticles were chosen to as the core functionalized by mercaptoacetic acid due to the low toxicity and magnetic properties for the activation of H2O2. The magnetic of Fe3O4@ MIL-100(Fe) microspheres is beneficial for the adsorption of MB and the separation from the bulk solution, indicating a high recyclability and degradation efficiency.28 Besides, the optimal shell thickness figured from various tunable thickness was about

salicylidene)) chelated the square-pyramidal Fe(III) atom for a higher-dimensional structure, making them difficult to crystallize during the facile hydrolysis. Interestingly, three independent CdII atoms were held together with the assistance of eight carboxylate groups (Figure 5A). Meanwhile, the same group proposed a heterotrimetallic organic framework with BaII and NaI.31 The coordination environments of BaII and NaI atoms coordinate to external carboxylate groups, whereas the FeIII ion form an (FeL)2(μ2-OH) dimer bridged by a μ2-OH anion resembling the previous study (Figure 5B). 20257


Review

ACS Applied Materials & Interfaces

Figure 2. (A) Illustration of 1D chain, 2D MOFs, and 3D MOF. Panel A are reprinted with permission from ref 100. Copyright 2010 Royal Society of Chemistry. (B) SEM and TEM image of hollow structure. Panel B are reprinted with permission from ref 40. Copyright 2016 Royal Society of Chemistry.

rate of MIL-53(Fe) with conventional electric (CE) heating, ultrasound and microwave, and the result showed that the US irradiation possessed the highest rate for both of nucleation and crystal growth.47 In addition to the traditional MILs and NH2MILs, various of attractive functionality were introduced by novel metalloligands as building blocks, providing sites for other unsaturated metal centers.48 3.1. MILs and NH2-MILs. MIL-type structures (for Materials Institute Lavoisier) are the most important MOFs synthesized for the environmental remediation. As briefly illustrated in Table 3, the fundamental conditions for the synthesis of common MILs and NH2-MILs, and the microwave-assisted method shows a considerable superiority to the solvothermal synthesis. After comparing numerous present works, we found that the amount of solvent and the time of heating could be adjusted even for the fabrication of the same MOFs, aiming at a suitable size to the different requirements. Meanwhile, the volume capacity, the stirring time, and postprocessing for the further purification are more flexible, whereas the ratio of metal and linker is stable. However, it is

50 nm, whereas the previous study paid less attention to this parameter.42 A suitable shell thickness directly affected the generation of •OH from H2O2 with a lower requirements for the excitation from valence band to conduction band (Figure 6b). Moreover, the Fe3O4@MIL-101(Fe) also have been used for the activation of PS.43 The coordinate activation was accomplished by the coexistence of mixed-valence iron oxides, and the Fe−O clusters of MOFs maintain the whole structure (Figure 6c). The noble metals (e.g., Au, Pd, and Pt) for the improvement of traditional Fenton process were also introduced as a combined strategy of 3D structure for the Fenton-like reaction.36,44

3. SYNTHESIS Especially for the preparation of iron-containing MOFs in the field of environmental remediation, the recent upsurge more and more concentrated on high stability and space time yields.45,46 On the basis of the most common solvothermal synthesis for MILs, Haque et al. compared the crystallization 20258


Review


Figure 3. (A) SEM image of 1D microrod: (a, b) Fe3O4, (c, d) MIL-53(Fe) and (e, f) MHMCs. Panel A is reprinted with permission from ref 17. Copyright 2014 Royal Society of Chemistry. (B) SEM image ultrathin 2D structure. Panel B is reprinted with permission from ref 23. Copyright 2015 Elsevier. (C) The schematic diagram of commonly used organic ligand structures (structures obtained from terephthalic acid,86 2aminoterephthalic acid,50 trimesic acid,21 fumaric acid,73 2,2′-bipyridine-5,5′-dicarboxylic acid40).

oxide nanoribbons,51 the natural graphene powder for graphene oxide,52 and graphite for graphite oxide.53 Moreover, the thickness of MIL-100(Fe) shell could be adjusted to a optimal size with a tunable time under ultrasonication.42 In addition to the core−shell structure, the coexistence of one-dimensional MIL-53(Fe) microrods and Fe3 O 4 in MHMCs was accomplished by one-pot solvothermal process illustrated in Figure 9a, further confirmed by FTIR spectra and XRD result. Nevertheless, the Fe3O4 composites is not necessary for the introduction of magnetism. The reduction of metallic nodes can also obtain the embedded Fe3O4 nanoparticles in the ultrathin MIL-88B(Fe) nanosheets.54 Different from the conventional synthesis method of MIL88B(Fe), the solvent changed into the ethylene glycol (EG) with additional trisodium citrate and anhydrous sodium acetate, and then heated at 200 °C for 10 h. The presence of ferric citrate was exhibited by mahogany suspension, further confirmed with the formation of surface wrinkles on spherical aggregates as illustrated in Figure 9b. Besides, a palmitatemodified method for the MIL-88B(Fe) was proposed for a better dispersion in the organic phase.55 As seen in Figure 9c, the characteristic of polymer shell was modified with photolabile oligomers, whereas the palmitic acid was used to adjust the hydrophobicity of MIL-88B(Fe) with uniform crystal size.

nearly impossible to gain the high-quality and pure MIL88B(Fe) crystals due to the same initial solution as the MIL53(Fe) and MIL-101(Fe).49 The modification of amino group was accomplished by introducing amino organic ligands simply.50 The structure of iron fumarate MIL-88A(Fe) as well as different crystals of MIL-88B(Fe) (Figure 7A). Among various of MIL-88-type materials, Fe-based MIL-88B-NO2, MIL-88A, MIL-88B, and MIL-88B-2OH solids were fabricated at the gram scale for the NO adsorption (Figure 7B). Figure 7C clearly shows the specific shape of MIL-88B(Fe) and NH2MIL-88B(Fe). 3.2. MIL-Based Materials. On the basis of the traditional MILs materials, Table 4 shows the classical MIL-based materials, which shows that the noble metal, graphene (or graphite) oxide, and Fe3O4 could be introduced by additional regent or composite. Interestingly, the M@MIL-100(Fe) (M = Pd, Au, and Pt) was directly fabricated on the MIL-100(Fe) with the protection of PVP, indicating a relatively integral structure of MIL-100(Fe) retained after the reflux process further confirmed by the SEM image.44 Nevertheless, the rest of the synthesis methods must be carried out under ultrasonication for the adequate mixing of MOF precursor and introduced composite. With various form seeing in Figure 8A, B, graphite materials in the present paper were come from different approaches, including the MWCNTs for graphene 20259


Review


Figure 4. Illustration of different iron sites with 3D structure: (a) Cubic lattice structure of Fe−Co PBAs. Panel a is reprinted with permission from ref 24. Copyright 2015 Elsevier. (b) Pillared-layer-type structure of Fe(pz)[MII(CN)4]. Panel b is reprinted with permission from ref 25. Copyright 2009 Wiley. (c) Reversible spin state of Fe-BTTri. Panel c is reprinted with permission from ref 74. Copyright 2016 American Chemical Society.

carried out with H4L, FeCl 3·6H2O, DMF, water, and ethanol.31,41

3.3. MIL-Free Materials. The MIL-free materials have not been investigated systematically due to the limited researches, and solvothermal synthesis for them always carried out without assistance. One of the MILs-free materials is synthesized with organic ligands, and the DMF is necessary for a better crystallinity and solution. The mentioned Fe-bpydc could be obtained from hydrothermal reaction between 2,2′-bipyridine5,5′-dicarboxylic acid (H2bpydc) and Fe(ClO4)2 with a solvent of DMF and H2O.40 The novel Fe-BTTri was synthesized though the mixture of DMF, 1,3,5-tris(1H-1,2,3-triazol-5yl)benzene (H3BTTri), dimethylformamidium trifluoromethanesulfonate, and FeCl2 at 120 °C for 10 days with continuous stirring.26 Another important part is heterometallic MOFs with iron content, and most of the synthesis method carried out with water as solvent have been adopted for the degradation in aqueous solution. The mixture of K4[Fe(CN)6], Me3SnCl, and H2O was used to synthesize organotin-polymer [(Me3Sn)4Fe(CN)6].27 The K3[Co(CN)6] have been developed to prepare FeII−Co PBA and FeIII−Co PBA for the decomposition of H2O2with FeCl2·H2O and FeCl3·6H2O respectively.24 Moreover, the extra additive CoCl2·6H2O and PVP were used to fabricate FexCo3−xO4 nanocages for the activation of PMS derived from FeyCo1−y-Co PBAs nanospheres.23 Nevertheless, the synthesis with Schiff base ligands frequently with DMF for the presence of H4L (1,2-cyclohexanediamino-N,N′-bis(3methyl-5-carboxysalicylidene)). Interestingly, the preparation of metalloligand H2(Fe-L)Cl accomplished with a mixture of H4L, FeCl3·6H2O and ethanol for the [Zn2(Fe-L)2(μ2-O)(H2O)2]·4DMF·4H2O with ZnCl2 was required, whereas the synthesis of [Cd2(Fe-L)2(μ2-O)(H2O)2]·2DMF·H2O with CdCl2·2.5H2O and heterotrimetallic [BaNa(FeL)2(μ2−OH)(H2O)]·DMF·2H2O with BaCl2·2H2O and NaCl was directly

4. APPLICATION IN ENVIRONMENTAL REMEDIATION 4.1. Adsorption with Iron-Containing MOFs. Ironcontaining MOFs own excellent adsorption and desorption properties for the distinctive structure at specific conditions. With reasonable hydrothermal stability and hydrophilicity, MIL-100(Fe) was used as water absorbent for the fresh water production,56 and adsorption heat-transformation.57 Water is nontoxic and reuseable, and reproduction of clean water greatly reduces the environmental pressure caused by the contaminants dissolved in water. 4.1.1. Adsorption of Inorganic Contamination. Hazardous inorganic contamination in drinking water represents a serious health threat, and fluoride is classified as one of them for the potential risks to the dental and skeletal fluorosis. In 2016, Ke et al. successfully prepared the MIL-88A as the adsorbent of fluoride in water through solvothermal reaction, and found the adsorption of fluoride is spontaneous.58 Determined by the fluoride-selective electrode, the coexistence of bicarbonate, sulfate, chloride, nitrate, and phosphate have no interference with the removal of fluoride because of the high selectivity. Meanwhile, the dilute hydrochloric acid in wastewater discharge aggravate causticity of water, in 2016, Lan et al. evaluated the adsorptive efficiency of six kinds of water-stable MOFs (MIL53(Cr), MIL-100(Cr), MIL-101(Cr), MIL-100(Fe), MIL96(Al), and UiO-66) for the hydrochloride in dilute aqueous solution.59 Compared to the MIL-100(Fe) in the repeated adsorption process for the removal of hydrochloric acid, UiO66 possessed a higher adsorption capacity and stability. 4.1.2. Adsorption of Organic Contamination. In addition to the application in the water purification, iron containing 20260


Review


Figure 5. Schematic illustration of HMOFs with Schiff base ligand: (A) Coordination environments, (FeL)2(μ2-OH) dimer, and 3D structure of [Cd2(Fe-L)2(μ2-O)(H2O)2]·2DMF·H2O. Panel A is reprinted with permission from ref 41. Copyright 2015 ChemPubSoc Europe. (B) Coordination environments, (FeL)2(μ2-OH) dimer and 3D structure of [BaNa(FeL)2(μ2-OH)(H2O)]·DMF·2H2O. Panel A is reprinted with permission from ref 31. Copyright 2015 American Chemical Society.

individually for the low surface area. Still for the adsorptive desulfurization (ADS), nonporous MOFs could be composed with typical porous MOFs aiming at a higher efficiency via πcomplexation (Figure 10a). MIL100(Fe) was composed with another CP (Cu2(pyz)2(SO4)(H2O)2)n as porous CP/MOF composites for a facile way to utilize or disperse the active sites of nonporous MOFs by Hasan et al.37 The DMDBT, BT and dibenzothiophene (DBT) were used as sulfur-containing compounds for the evaluation, and the result shows that the maximum adsorption capacities of CP/MIL100(Fe) (128 mg/ g) were higher than MIL100(Fe) (114 mg/g). With both of the magnetism and superior performance in the adsorption of organic matter, iron containing MOFs have been successfully applied to the drug delivery. Reasonably, as a nonnoble metal, iron-containing MOFs own a better prospect in the removal of organic contamination. In the recent year, organic acids were used in industry in large amounts as raw material, in 2016, Zhang et al. adopted the same six kinds of reported water-stable MOFs as Ke et al.58 for the adsorption of acetic acid.61 In addition to the measurement of kinetic parameters, several thermodynamic parameters were also used to evaluate the capacity of adsorption, and the calculation

MOFs were also investigated by advanced theory. Especially for the calculation of multielectron systems, DFT is superior to the wave function, which is recognized as a powerful tool for evaluating adsorption mechanism of MOFs. In 2016, Chen et al. investigated the removal of sulfur compounds by DFT in Materials Studio 5.5 software.32 Metal cation and organic ligands of MOFs has a different efficiency in the adsorption process, and the high polarity in the ligand will strengthen adsorption of sulfur compound. Moreover, among the metal centers with coordinatively unsaturated sites (CUS), the binding energy of iron-containing MOFs (Fe-MOF-74, FeMOF-101, Fe-MOF-199) is stronger than copper and zinc. In 2015, Li et al. first examined the adsorbate−adsorbent interaction by comparing 5 kinds of MOFs (MIL-53(Fe), MIL53(Cr), MIL-101(Cr), MOF-5 (Zn4O(BDC)3), and HKUST-1 (Cu3(BTC)2) with the benzothiophene (BT), 4,6-dimethyldibenzothiophene (DMDBT), and thiophene.60 Interestingly, when the window diameter of MOFs is suitable for the molecular size of sulfur compounds, the adsorbate−adsorbent interaction much matters, whereas high porosity cannot guarantee the excellent adsorption. One of significant characteristics of mentioned MOFs is porous structure while it is difficult to utilize nonporous MOFs 20261


Review


Figure 6. Illustration of classical Fe3O4 core with MILs shell for the catalytic degradation: (a) Fe3O4@MIL-100(Fe) first proposed for the activation of H2O2. Panel a is reprinted with permission from ref 28. Copyright 2013 Royal Society of Chemistry. (b) Optimal thickness of MIL-100(Fe) shell were figured out with tunable method. Panel b is reprinted with permission from ref 42. Copyright 2015 ChemPubSoc Europe. (c) Fe3O4@MIL101(Fe) was adopted for the activation of PS. Panel b is reprinted with permission from ref 43. Copyright 2016 Springer.

Table 3. Part of the Methods for the Synthesis of MILs and NH2-MILs compd

metal

linker

ratio/solvent

MIL-53(Fe)

FeCl3·6H2O

terephthalic acid (H2BDC)

1:1/DMF

MIL-88A(Fe) MIL-88B(Fe) NH2-MIL88B(Fe) MIL-100(Fe)

FeCl3·6H2O FeCl3·6H2O FeCl3·6H2O

1:1/water 1:1/DMF 1:1/DMF

iron powder

fumaric acid terephthalic acid 2-aminoterephthalic acid (NH2− BDC) trimesic acid (H3BTC)

MIL-101(Fe) NH2-MIL101(Fe)

FeCl3·6H2O FeCl3·6H2O

terephthalic acid 2-aminoterephthalic acid

2:1/DMF 2:1/DMF

1.5:1/hydrofluoric acid, nitric acid and water

conditions and time

ref

150 °C for 2 h 150 °C for 15 h 65 °C for 16 h microwave-assisted for 1−10 min microwave-assisted for 1−10 min

86 92 73 50 50

150 150 110 120

°C °C °C °C

for for for for

24 12 20 24

h h h h

21 65 93 83

99.6 kJ/mol for MO) and ΔS (300 J/(mol K) for MB and 441 J/(mol K) for MO) values obtained from van’t Hoff plot with the (−slope × R) and (intercept × R), respectively, the negative ΔG for the dye adsorption on MOF-235 is caused by a large positive ΔS rather than the positive ΔH. The influence of framework metal ions was compared by Tong et al. with MB and MO, and provided by the characterization of FT-IR, the MIL-100(Fe) exhibits a higher uptake, whereas the MIL-100 (Cr) is able to selectively adsorb MB from a MB-MO mixture.62 In 2014, Tsai et al. synthesized MIL-100 (Fe) for the removal of acid orange 7 (AO7) at a relatively low pH (at 3.0), and pseudo-second-order kinetic model was considered as a more suitable model than pseudosecond-order kinetic model, which is surely different from the dye adsorption on MIL-100 (Fe).65 The appropriate amount of additive can modify the MOFs for a larger saturated adsorption amount of dye, although the

results of ΔG, ΔH, and ΔS, further confirming the superiority of UiO-66. There are several excellent papers summarizing the dye capture behavior,62 and mechanisms for selective adsorptions,63 confirming that iron-containing MOFs are considered as promising adsorbents for dye adsorption. The large adsorption uptakes of dye with iron containing MOFs can be explained for the potentially strong electrostatic interactions, porous structure and relatively heterogeneous surface (means a polarity).62 In 2010, Haque et al. removed the cationic dye methylene blue (MB) and anionic dye methyl orange (MO) by iron terephthalate (MOF-235) using a pseudo-first-order kinetic model, which shows a more outstanding capacity of dye adsorption than activated carbon.64 The concentration of MB (C16H18ClN3S) and MO (C14H14N3NaO3S) was detected by Shimadzu UV spectrophotometer at 665 and 464 nm, respectively. Analysis from the ΔH (63.1 kJ/mol for MB and 20262


Review


Figure 7. (A) Top: view of MIL-88(Fe) and the constitutive ligands. Bottom: structure of dried form and open form MIL-88B(Fe). (B) NO adsorption−desorption isotherms on flexible MIL-88(Fe). Panel A and panel B are reprinted with permission from ref 73. Copyright 2013 American Chemical Society. (C) SEM images of (a, b) MIL-88B(Fe) and (c, d) NH2-MIL-88B(Fe). Panel C is reprinted with permission from ref 50. Copyright 2013 ChemPubSoc Europe.

Table 4. Synthesis of MIL-Based Materials Applied in Environmental Remediation compd

regent/composite

Pd@MIL-100(Fe) Au@MIL-100(Fe) Pt@MIL-100(Fe) MIL-53(Fe)-graphene

H2PdCl4 HAuCl4·4H2O H2PtCl6·6H2O graphene oxide nanoribbons

MIL-100(Fe)/graphite oxide

graphite oxide

MIL-100(Fe)/graphene oxide

graphene oxide

Fe3O4@MIL-100(Fe)

mercaptoacetic acid (MAA)-functionalized Fe3O4

Fe3O4@MIL-101(Fe)

wet magnetic Fe3O4

brief method

ref

stirred with PVP (Polyvinylpyrrolidone), H2O, ethanol and MIL-100(Fe) refluxed at 90 °C for 3 h sonicated with DMF for 120 min stirred with FeCl3·6H2O, terephthalic acid, DMF Heated to 170 °C for 24 h stirred and sonicated with Fe powder, trimesic acid, hydrofluoric acid, nitric acid and water heated to 150 °C in 8 h maintained at 150 °C for 4 days stirred with Fe powder, trimesic acid, hydrofluoric acid, nitric acid and water heated to 160 °C for 8h sonicated with FeCl3 and ethanol for 15 min sonicated with trimesic acid at 70 °C for 30 min sonicated with FeCl3 and ethanol for 3 min sonicated with trimesic acid at 70 °C for 15 min sonicated with PVP and DMF for 10 min sonicated with FeCl3·6H2O for 10 min sonicated with terephthalic acid for 10 min heated at 110 °C for 20 h

44, 89

51

53

52 28 42 43

reference of MOF0 (0 wt %). Although MOF0 shows the least amount of solvent in thermogravimetric analysis (TGA) with no additional GO, the characterization of FT-IR spectra showed no obvious differences for the quite low concentration. In recent years, organoarsenic compounds were reported as emerging pollutants in groundwater for the synthesis in pesticide manufacturing, and the degradation method tried to convert the As(III) to As(V) with assistance of adsorption.66 In 2014, Jun et al. adsorbed p-arsanilic acid (ASA, C6H8AsNO3)

functionalization methods would have more diverse applications in the gas removal and degradation process. In 2015, Yi et al. employed different graphene oxide (GO) contents to the preparation of (MIL-100)/graphene oxide composites (MOFs/ GO) for the removal of MO and methyl red.52 The introduction of GO increased the pore volume and specific surface area, specifically, MOF1 (0.5 wt %), MOF2 (2.5 wt %), and MOF3 (5.0 wt %) increased to 40, 33, and 35% in pore volume and 37, 32, and 35% in specific surface area with the 20263


Review


Figure 8. (A) SEM images of (a) GO, (b) MIL, (c) MIL-GO1, and (d) MIL-GO2. Panel A is reprinted with permission from ref 53. Copyright 2011 Wiley. (B) SEM images of (a) MIL-53(Fe) and (b) M53/GR-8. TEM images of (c, d) M53/GR-8. Panel B is reprinted with permission from ref 51. Copyright 2016 Elsevier.

Meanwhile, in 2012, Petit compared the capacity of MIL100(Fe), MOF-5, HKUST-1, GO, and graphite for the removal of NH3, H2S, and NO2, and found that the lone pair of electron on these toxic gases might weaken the bonds between the organic ligands and center metallic sites of MOFs contributing to the release of organic ligands and metals.72 As another environmental concern, nitric oxide also play a vital role in the regulation of nervous, cardiovascular, and immune systems. In 2013, McKinlay et al. investigated the adsorption and delivery of NO over a series of Flexible MIL88(Fe), which finally concluded the best performance of MIL88A(Fe).73 The result from ex situ XRD and in situ IR spectroscopy shows that the physical adsorption on the very narrow pores and the chemical adsorption on iron(II) or iron(III) CUS were dominant mechanism of NO adsorption. Compared to the abundant toxic gases in atmosphere, carbon monoxide possesses both a deadly toxicity and regulatory function, putting forward a higher requirement that means accurately controlled adsorption and desorption. In 2013, Ma et al. precisely prepared crystals of MIL-88B(Fe) (length of about 2 μm and a diameter of 1 μm) and NH2-MIL-88B(Fe) (a length of about 1.5 μm and a diameter of 300 nm) by microwave-assisted solvothermal method.50 Myoglobin was used to evaluate the release of CO in physiological buffer, the half-life of MIL-88B(Fe) and NH2-MIL-88B(Fe) were 38 and 76 min, respectively. The CO-loaded material with large “breathing effect” owns considerable therapeutic applications. In the latest research, in 2016, Reed et al. reported Fe-BTTri (Fe3[(Fe4Cl)3(BTTri)8]2·18CH3OH) with highly selective CO adsorption over CO2 and ethylene, and confirming that the presence of N2, CO2, CH4 and H2 will not disturb the adsorption process even at very low pressures.74 To the best of our knowledge, ideal adsorbed solution theory (IAST) selectivity for CO-containing mixtures exhibit the highest values among any adsorbent-based gas separation, providing a possible way to the separation of CO produced in iron and steel production. 4.2. Catalytic Degradation. Several excellent reviews have been published previously, focusing on classical iron involved catalysts which contain the homogeneous catalysis with Fe2+ or Fe3+,75 and heterogeneous catalysis with various iron-containing materials (silicas and zeolites,76 clays.76,77), concentrating on photo-Fenton (PF),77−79 andelectro-Fenton (EF).80 As ex-

and roxarsone (ROX, C6H6AsNO6) over MIL-100(Fe) with excellent capacity of adsorption and regeneration rapidly, which highly surpass the performance of MIL-100-Al and MIL-100Cr.67 As shown in Figure 10b, the adsorption and desorption mechanism (coordinatively unsaturated sites (CUSs) and open metal sites (OMSs)) of ASA were exhibited, and the lowest absolute adsorption energy of water and the highest absolute replacement energy might be the direct reason for superiority of MIL-100(Fe) among analogous MIL-100 species. Meanwhile, the presence of the As-OFe bond also enhanced the adsorption shown by FT-IR spectrum. 4.1.3. Adsorption of Toxic Gas. As the toxic gases being released into the atmosphere are a worldwide threat of growing concern, Barea et al. have published an brilliant tutorial review for the toxic gas removal with MOFs, and the iron-containing MOFs play a vital role in this field.68 The conventional separation of gas was carried out according to the polarity or hydrophilicity/-phobicity. Nowadays, if the adsorbate’s length and the adsorbent’s cavity size match well, selective adsorption of gas can be carried out more accurately according to the length.69 Moreover, the ideal adsorbed solution theory (IAST), DFT and grand canonical Monte Carlo simulations (GCMC) were also introduced as computational procedures for the comprehensive study adsorptive separation mechanism of various metal-substitution to volatile organic compounds (VOCs).70 Iron-containing MOFs have been successfully adopted for the adsorption of ammonia, nitric oxide and nitrogen dioxide which largely contributed to the formation of gas- and particlephase pollutants in photochemical smog.71 In 2011, Petit et al. evaluated the limits of prepared well-defined MIL-100(Fe)/GO composites for the adsorption of ammonia in dynamic conditions, and the adsorption capacity decrease due to a lower acidity of composites caused by excess water.53 NH3 breakthrough dynamic test were designed for the measurement of NH3 breakthrough capacity with electrochemical sensor (Multi-Gas Monitor ITX system). The interactions of the metallic sites of MIL and oxygen groups of GO contribute to the coordination of the MIL units (finally contributing to the formation of the whole framework) via various possible ways. Brönsted interactions were considered as the main mechanism of ammonia adsorption, and this characteristic of the whole framework would be cut down by relatively large GO content. 20264


Review


Figure 9. (a) Schematic diagrams for the fabrication of MIL-53(Fe) hybrid magnetic composites (MHMCs). Panel a is reprinted with permission from ref 17. Copyright 2012 Royal Society of Chemistry. (b) The morphology and schematic diagrams of the NHMMs: (A) SEM and TEM images at 1, 2, 4, and 7 h. (B) Corresponding illustration of the evolution process. Panel b is reprinted with permission from ref 54. Copyright 2016 ChemPubSoc Europe. (c) Synthesis and application of MOFs encapsulated in photolabile capsules: (A) Palmitate-modified P-MIL-88B and photolabile oligomers. (B) MOF crystals inside. (C) Release of homogeneous iron species under UV light. Panel c is reprinted with permission from ref 55. Copyright 2015 American Chemical Society.

in stirring condition at ambient temperature and neutral pH.20 As a tiny structural motif, Fe3-μ3-oxo clusters containing MOFs is predominant in the field of photocatalysis for the small band gap, and the presence of Fe(II) in its framework largely promoted the COD removal with similar stability up to 300 °C according to the results of TGA. Compared to the NH2-MIL53(Fe) and MIL-53(Fe) synthesized in static condition, the synthesis of Fe(BDC) (DMF,F) shaping a rodlike morphology of bulky irregular shape under agitation was found a best performance at 3 days (Figure 11A). After a year, the same

cellent heterogeneous catalysts, iron-containing MOFs mainly degrade organic pollutants by generating •OH or SO4•−, and the light and electricity both have been introduced as powerful enhancements. 4.2.1. Hydroxyl Radical Catalysis. Iron-based MOFs generated •OH in the heterogeneous Fenton process with both a standard redox potential of 1.8−2.7 V and excellent properties of organometallic coordination, avoiding a secondary treatment for the mild conditions.21 In 2015, Sun et al. synthesized Fe(BDC) (DMF,F) for the degradation of Phenol 20265


Review


Figure 10. (a) Schematic diagram of the fabrication of CP/MIL100(Fe). Panel a is reprinted with permission from ref 37. Copyright 2015 American Chemical Society. (b) Suggested adsorption mechanism of MIL-100(Fe) for CUS or OMS. Panel b is reprinted with permission from ref 67. Copyright 2014 ChemPubSoc Europe.

Figure 11. (A) SEM images of Fe(BDC) (DMF,F) stirring condition for (a) 1, (b) 2, (c) 3, and (d) 4 days. Panel A is reprinted with permission from ref 20. Copyright 2015 Royal Society of Chemistry. (B) SEM images of Fe(BDC) (DMF,F) with different n(FeCl3)/n(FeCl2). Panel B is reprinted with permission from ref 81. Copyright 2016 Royal Society of Chemistry.

and Fe3+ can be detected by 57 Fe Mössbauer spectra founded that the maximum amount of Fe2+ prepared with the mixture of FeCl2 and FeCl3 is 26.0%. After 3 cycles, all the MIL-53 type materials exhibit high stability in the COD removal, H2O2 conversion, and phenol degradation. In addition to the 1,4-benzenedicarboxylate, the 2,2′bipyridine-5,5′-dicarboxylate was also adopted as organic ligand

group improved the structure of Fe(BDC) (DMF,F) based on the previous study, and the concentration of Fe(II) in Fe(BDC) (DMF,F) has reached a controlled level by adjusting the ratios of n(FeCl3)/n(FeCl2).81 As seen in Figure 11B, the morphology of series of Fe based MOF materials change from small shape to big triangular prism with increasing Fe2+ concentration in obvious regularity. The coexistence of Fe2+ 20266


Review


ligands and direct absorption on the Fe−O clusters. The presence of H2O and CO2 confirm the 79.4% conversion efficiency of toluene mineralization, whereas the benzoic acid and benzaldehyde were displayed by in situ FTIR as intermediate. The tunable conditions have been controlled successfully for the photocatalytic process in terms of wavelength and products.84,85 The hydroxylation of benzene is the representative of selective photocatalysis based on Fe containing MOFs, in 2015, Wang et al. suggested a one-step selective benzene hydroxylation process over MIL-100(Fe) and MIL-68(Fe) after 24 h irradiation, aiming at a sustainable and economical process for phenol production.85 The result of ESR spectra confirm the Fe−O clusters enhance the Fenton-like with the assistance of visible light, and the optimum benzene conversion carried out over MIL-100(Fe) with a H2O2/benzene ratio of 3:4 was 30.6%. Ai et al. adopted MIL-53(Fe) for the activation of H2O2 for the degradation of Rhodamine B (RhB), and the capture of •OH revealed the consumption of H2O2 mainly contributed to the heterogeneous Fenton process and immobilization of photogenerated electrons.86 Terephthalic acid was used as probe molecule for the detection of •OH according to the fluorescence method. Pretreated ITO was used for the fabrication of the MOF electrodes with MIL-53(Fe) working on a electrochemical workstation, carring out the evaluation of photocurrent and the Mott−Schottky measurements of band positions though impedance-potential model. Moreover, the same group synthesized the multifunctional MHMCs for the photodegradation of organic pollutant (p-nitrophenol (PNP) and Rh B) and photoelectrochemical water oxidation under visible light.17 The superparamagnetic characteristic of MHMCs is distinctive among the most MOFs for the nearzero remanence and coercivity at room temperature showing in the magnetization hysteresis curve. Compared to the transient photocurrent responses on the MIL-53(Fe), the photocurrent response on MHMCs is more reproducible, steady, and remarkable, providing a new physical insight for the design of advanced MOFs for energy and environmental applications. For the diversification of iron-containg MOFs, heterometallic organic frameworks (HMOFs) have been designed for the degradation of POPs as a improvement of conventional catalysts, which containing heterobimetallic (e.g., organotinpolymer [(Me3Sn)4Fe(CN)6],27 Fe−Co PBAs,24 [Cd2(FeL) 2 (μ 2 -O)(H 2 O) 2 ]·2DMF·H 2 O and [Zn 2 (Fe-L) 2 (μ 2 -O)(H2O)2]·4DM·4H2O41) and heterotrimetallic (e.g., [BaNa(FeL)2(μ2-OH)(H2O)]·DMF·2H2O)31). In 2012, Etaiw et al. synthesized organotin-polymer [(Me3Sn)4Fe(CN)6] for the degradation of MB under UV light, and the 3D-polymeric network consists of Me3Sn cations connected by [Fe(CN)6]4− building blocks.27 ROS were identified by photoluminescence probing technology with disodium salt of terephthalic acid. Nevertheless, the active transition-metal centers is organotin(IV), the Fenton reaction play a practical role in the oxidative discoloration by generating •OH. The result of FT-IR spectra revealing the specific location of two forms of cyanide ligand, which not only connecting the iron atom and tin atom but also existing at the end of the carbon chain freely. Co, the most similar metal to Fe, and Co-MOFs has been applied to degraded dibutyl phthalate (DBP) under visible light.87 The combination of Fe and Co were developed by Li et al. for the removal of RhB, namely Fe−Co PBAs with both Fe(II) and Fe(III).24 The deep exploration of Mössbauer spectroscopy

for the synthesis of Fe-bpydc by Li et al. aiming at a high efficiency in near neutral pH.40 The data of total turnover number (TON) show the brilliant endurance of Fe-bpydc by supplementing phenol and H2O2 to the initial concentration repeatedly. It is noteworthy that the H2O2 utilization efficiency of Fe-bpydc is higher than traditional homogeneous Fenton for the negligible H2O2 consumption in the absence of organics, and the successful application of Fe-bpydc indicates that the minimization of MOFs is reasonable. Moreover, In 2015, Lv et al. demonstrated the efficiency of MB removal though the combination of adsorption and Fenton process by comparing the MIL-100(Fe), Fe3O4 and FeII@MIL100(Fe) at wide pH range of 3.0−8.0.21 Interestingly, the FeII@ MIL-100(Fe) exhibited the best efficiency in the Fenton degradation while the MIL-100(Fe) is better in the adsorption and total degradation process due to the additional surface area of 418 m2g−1. The results of turn over frequency (TOF) value further confirmed superiority to each active site of FeII@MIL100(Fe) with the synergistic effect between Fe(II) and Fe(III) (Figure 12).

Figure 12. TOF for the evaluation of different catalyst to the removal of MB. Reprinted with permission from ref 21. Copyright 2015 Elsevier.

As an economical and environmental external energy, visible light has been wildly used to induce a high-preformance photocatalysis with Fe-containing MOFs. The presence of semiconductive property and repetitive π-bond structure in Fe containing MOFs largely assisted the photogeneration of hydroxyl radicals or reactive oxygen species (ROS), but the degradation of MOFs in Fenton-like conditions must be comprehensively evaluated for the safety of environmental applications. In 2016, Liu et al. probed the performance of isoreticular MIL-53s (MIL-53(Fe), MIL-53(Cr) and MIL53(Al)) in the generation of ROS, comparing the effect of ROS on the human hepatocyte (HepG2) cell line and diclofenac.82 The incubation of HepG2 cell enrich the cytotoxicity evaluation of the ROS and degradation species of MOFs, and the excellent removal efficiency of diclofenac ensure the usefulness ROS. Moreover, the degradation of VOCs in atmosphere with functionalized Fe-based MOFs has been carried out under visible-light irradiation by Zhang et al.83 The distinctive hexagonal microspindle structure of NH2-MIL-101(Fe) exhibits an improvement for the degradation of toluene, predominantly explaining by the photogeneration of charge carriers through indirect absorption of the visible light on the modified organic 20267


Review


Figure 13. (a) Schematic diagrams of mechanism for the photodegradation of PPCPs over Pd@MIL-100(Fe). Panel a is reprinted with permission from ref 44. Copyright 2015 Elsevier. (b) Schematic diagrams of photogeneration route for fabrication of M@MIL-100(Fe). Panel b is reprinted with permission from ref 89. Copyright 2015 Springer.

out an ongoing project involving the design of Fe(III)containing HMOFs.31,41 In 2015, Li et al. introduced two functionalized Schiff-base ligands for the synthesis of binary HMOFs for the photodegradation of 2-chlorophenol (2-CP), and the optimal pH value is 3 for the relevant 73% photocatalytic activities.41 Moreover, the same group synthesized a heterotrimetallic compounds with Schiff base and FeIII/ BaII/NaI, evaluating the removal efficiency of 2-CP, 3-CP, and 4-CP under visible light at different pH.31 A possible mechanism for the generation of •OH was illustrated in Figure 14, the basic [L-FeIII] units initially generating [L-FeIII-OH] species, and the presence of H2O2 contributing to the formation of [L-FeIII−OOH] species. The activation of visible-light irradiation undergoes a transition to excited state, easily generating the •OH with[L-FeVO] after the O−O bond splitting.

clearly identified the excellent redox cycling of iron species existing in efficient photo-Fenton process with the Fe−Co PBAs, ascribed to the existence of bundant vacancies and water coordinated iron sites in the Fe−Co PBAs highly enhance. Sodium azide was used to investigate the utilization of singlet oxygen (O21) by quenching the photo-Fenton process, proposing a novel degradation mechanism based on radical reaction. Pd has been used as a connection of Fe-containing catalyst for the heterogenerous Fenton process.88 In 2015, Liang et al. fabricated Pd@MIL-100(Fe) for the photodegradation of pharmaceuticals and personal care products (PPCPs) though a facile alcohol reduction method, facing a new requirements of the environmental restoration.44 The superiority of Pd@MIL100(Fe) were confirmed by a higher photoactivity than MIL100(Fe) without Pd NPs which eliminate the recombination of photoinduced electron−hole pairs. As seen in Figure 13a, the capture of photoinduced electrons were carried out by the H2O2 on Pd enhanced the Fenton-like reaction, and the photogenerated holes attributed to a higher efficiency cooperatively. At the same year, the same group fabricated a M@MIL-100(Fe) (M = Au, Pd, and Pt) degradation of MO and reduction of Cr(VI) though the immobilization of noblemetal nanoparticles acting as electron reservoirs on MIL100(Fe).89 M@MIL-100(Fe) was achieved over a facile photodeposition route as illustrated in Figure 13b, Pt particle with a size of 2 nm on the Pt@MIL-100(Fe) contributed to the integrative effect of light adsorption and more efficient separation of the photoinduced charge carrier. Compared to the classical heterobimetallic iron containing MOFs for the heterogenerous degradation, the investigation on the Schiff base ligands is limited to Ma’s group who had carried

Figure 14. Possible pathway for the degradation of chlorophenols over heterotrimetallic organic framework. Reprinted with permission from ref 31. Copyright 2015 American Chemical Society. 20268


Review

ACS Applied Materials & Interfaces Although numerous iron-containing MOFs have been synthesized and adopted for the environmental remediation at a lab-scale, the stability of these catalyst is unsatisfactory for the elimination of natural perturbation and toxicity in aquatic environment. Fortunately, the core−shell magnetic MOFs have been designed for a potential industrial applications. Zhang et al. successfully prepared durable Fe3O4@MIL-100(Fe) for the decolorization of MB under both visible light irradiation and UV−vis, which can be easily recycled and separated without obvious loss of photocatalytic activity.28 The conventional photocatalyst of C3N4 and TiO2 were compared to the novel MOFs combined with the Fe3O4 core, and the rate constant of Fe3O4@MIL-100(Fe) is much higher than them following the first-order kinetics. In the latest research, the thickness of MIL-100(Fe) shell even became tunable to the Fe3O4@MIL-100(Fe) structure aiming at a higher photocatalytic performance for the MB degradation, and the optimal thickness was found at ∼50 nm by Zhao et al.42 The generation of photoinduced electrons and holes were relayed to the F3O4 core directly improving the decomposite of H 2O 2. The tunable shell thickness is determined by assembly cycles, proposing a general method to develop more efficient, green and suitable photocatalysts for pilot-scale study. With the similar pattern to the core−shell structure, photocleavable polyurea shell were introduced for the fabrication of photocleavable capsules with iron containing MOFs. In 2015, Deleu et al. investigated the oxidation efficiency of MIL-88B(Fe) containing capsules for the tetramethylbenzidine (TMB) under UV light, and the MOFs loading, UV intensity and irradiation time were considered as a controlled factor for the photo reactivity.55 The dispersion in the emulsified organic droplets was accomplished though a hydrophobic layer of alkyl chains introduced by palmitate. Nevertheless, the low encapsulation yields and solvent incompatibility is still concerned. Moreover, Jin et al. prepared Fe3O4/MIL-88B(Fe) with hierarchical nanosheet structure for the degradation of MB and RhB as an alternative to the conventional photocatalyst.54 The light absorption range was broadened to 660 nm while the diffusion time of its open mesomacroporosity. For the Na-citrate/NaOAc assisting modification over Fe3O4, Fe3O4/MIL-88B(Fe) obtained an excellent magnetism reaching a 2 times higher efficiency. In the recent advance, the electricity was introduced as a more powerful enhancement of photocatalysis by dispersing MOF(2Fe/Co) in carbon aerogel (CA) cathode though modified hydrothermal reaction, and the •OH was not generated from additional H2O2 but in situ H2O2 (Figure 15). Zhao et al. adopted dimethyl phthalate (DMP) and RhB evaluating the efficiency of solar photoelectro-Fenton (SPEF) process, reaching a 85% DMP removal in 120 min and 100% RhB removal in 45 min at a wide pH range from 3.0 to 9.0.90 The stability of the MOF(2Fe/Co)/CA cathode was convincing because of the relatively low iron and cobalt leaching, according to the analysis of ICP−AES. 4.2.2. Sulfate Radical Catalysis. The redox potential of SO4•− is up to 2.5−3.1 V mainly generated by PMS and PS activation with a higher selectivity, possessing a half-life period of 30−40 μs over a wide pH range.91 Interestingly, we found that the oxidation procedures with iron-containing MOFs over SO4•− frequently cooperated with •OH (Figure 16). In 2016, Gao et al. applied the MIL-53(Fe) to the degradation of AO7 mediated by PS under visible LED light excitation at near-

Figure 15. Schematic diagrams of MOF(2Fe/Co)/CA cathode and the possible pathway for the degradation of DMP and RhB. Reprinted with permission from ref 90. Copyright 2016 Elsevier.

Figure 16. Cooperation of sulfate radical and hydroxyl radical for the degradation of AO7 over MIL-53(Fe). Reprinted with permission from ref 92. Copyright 2016 Elsevier.

neutral pH.92 To overcome the recombination of electron− hole pairs, we used the optimum 2.0 mM PS as external electron acceptor for a higher efficiency during 14 on−off cycles. The results of photoluminescence spectra further identified that the capture of photoinduced electrons during MIL-53(Fe)/PS/Vis processes was accomplished by adding PS for a lower photocurrent. Meanwhile, the Fe3O4@MIL-101(Fe) composites with core−shell structure also have been adopted as heterogeneous catalysts to the activation of PS for the degradation of AO7 at pH 3.6 by Yue et al.43 The analysis of the Fe3+ leaching with inductively coupled plasma-atomic emission spectrometric (ICP-AES) was less than 15 μg L−1, which was the proof of excellent reusability and high stability. The adsorption of Febased MOFs can be efficiently combined with the PS activation, in 2016, Li et al. compared the adsorption and degradation efficiency of MIL-53(Fe), MIL-88B(Fe), MIL-100(Fe) and MIL-101(Fe) for AO7, and the MIL-101(Fe) exhibit the highest materials ability for both of adsorption and degradation.93 The crystallinity of the sample was detected by XRD, and well-defined diffraction peaks indicate a high crystallinity. Moreover, several excellent heterogeneous catalysts derived from iron-containing MOFs have been investigated for the activation of PS and PMS.23,94,95 In 2013, Qin et al. prepared magnetic CoFe2O4 nanocomposites with different molar ratio of MIL-100(Fe) and Co(NO)2·6H2O for the activation of PMS.94 It is noteworthy that the MIL-100(Fe) was used as both precursor and template of heterogeneous catalyst under various calcined conditions for the first time, and the morphology of precursor was preserved intact showing a higher catalytic performance for the oxidation of phenol. In 20269


Review


Figure 17. Schematic diagram for the preparation of MICN. Reprinted with permission from ref 95. Copyright 2015 Royal Society of Chemistry.

the conventional catalyst for the reduction of Cr(VI) under UV light.33 Among the research on the Cr(VI), in 2015, Liang et al. developed a bifunctional MIL-53(Fe) for the simultaneous degradation of dye and Cr(VI) under visible light, and a higher photocatalytic activity on Cr(VI) reduction was obtained over MIL-53(Fe) than conventional N-doped TiO2.96 As seen in Figure 18, the synergistic effect for a higher efficiency of Cr(VI)

2015, Li et al. degraded the bisphenol A (BPA) though the activation of PMS with FexCo3−xO4 nanocages, and x = 0.8 obtained the most uniform nanocages by adjusting amount of iron doping.23 The PBA FeyCo1−y[Co(CN)6]0.67·nH2O nanospheres were heated as precursor with tunable size, and the catalytic mechanism of FexCo3−xO4 nanocages was confirmed by XPS and 57Fe Mössbauer spectroscopy. Radical scavenging experiments were used to identified the •OH and SO4•−, whereas the GC-MS and LC-MS provided a possible degradation pathway. At the same year, Lin et al. carbonized the MIL-88A(Fe) to fabricate magnetic iron/carbon nanorod (MICN) for the degradation of RhB with PS and H2O2.95 Ultrasonication was also introduced to as an efficient external facilitator for the enhancement of the decolorization. The excellent magnetic property of MICN with manipulation experiment confirmed that the MICN can be recovered from water and uniformly dispersed in water with permanent magnet (Figure 17). 4.2.3. Related Photo and Heterogeneous Methods. Apart from the degradation of organic pollution though •OH or SO4•− carried out with iron containing MOFs, the reduction of Cr(VI) also have been deeply investigated with assistance of visible light for the semiconductor properties. Interestingly, the introduction of amino functionality would improve photocatalytic Cr(VI) reduction, in 2015, Shi et al. compared the Cr(VI) degradation efficiency of NH2-MIL-88B(Fe) and MIL88B(Fe), proposing a mechanism for the photocatalytic reduction.33 Interestingly, the electron generated from the direct excitation on the amino functionality would finally transferred to the Fe3-μ3-oxo clusters as an enhancement of the basic electron generation on the Fe3-μ3-oxo clusters. MIL53(Fe) and MIL-101(Fe) confirmed the phenomenon on the MIL-88B(Fe) with the investigation on their amine-functionalized analogue. Meanwhile, Dimitrova compared the Cr(VI) degradation efficiency of NH2-MIL-88B(Fe) and NH2-MIL-101(Fe) under visible-light irradiation, and a higher crystallinity of NH2-MIL101(Fe) attributed to a higher removal of Cr(VI) than NH2MIL-88B(Fe).34 The molar ratio of metal to ligand is the only parameter of different structure, exactly, the same molar ratio favored the production of MIL-88B(Fe) while the different molar ratio mainly formed MIL-101(Fe). The resulting UV spectra of all the iron(III)-based MILs and NH2-MILs exhibit an absorbance peak at 420 nm nearby, showing a superiority to

Figure 18. Schematic diagrams of the simultaneous degradation of Cr(VI) and organics bifunctional MIL-53(Fe) Reprinted with permission from ref 35. Copyright 2015 Elsevier.

removal was accomplished with the assistance of hole scavenger (e.g., ammonium oxalate and azo dyes) without H2O2. The new inroads into exploration of the MIL-53(Fe) indicating an actual application with the coexistence of toxic heavy metal ions and hazardous organics for the industrial wastewater treatment. Although Cr(VI) possesses a notorious toxicity, some of Cr(III) containing MOFs (e.g., MIL-53(Cr), MIL-101(Cr)) have been decorated with Fe-carbon oxides for the removal of reactive brilliant red X-3B, and additional citric acid (CA) keep the Fe2O3 aggregated inside (Figure 19). In addition to the Cr(VI), refinement and mining of uranium (U) has led to widespread aquatic pollution because of its bioaccumulation and high mobility in water, and Xiong et al. reported an ultrafast generation method for the Fe2O3@Zn-MOF-74 which could be used for the reduction of U(VI) though a surface 20270


Review


dimensional MIL-53(Fe)-graphene nanocomposite under visible light without additional oxidant.51 The graphene is prepared by multiwalled carbon nanotubes (MWCNTs) as functional entities, improving the photocatalytic activity by minimizing the recombination between photogenerated electron and hole, and the CCl4 plays a vital role as an electron scavenger aiming at more photogenerated holes as illustrated in Figure 21. The stability is convincing for the negligible loss of selective oxidation efficiency maintaining at least four cycles.

Figure 19. Schematic diagrams of decoration of Fe-carbon oxides on Cr(III) containing MOFs. Reprinted with permission from ref 101. Copyright 2015 Elsevier.

strategy.97 The combination of U(VI) adsorption on Zn-MOF74 and reduction over Fe(II) ions synergistically generated U(IV) (or UO2) with lower mobility under ambient conditions for the first time. In 2013, independent photoinduced hole-oxidation was accomplished by Laurier et al. for the response of series of iron(III)-based MOFs to visible light illumination at selected wavelengths for the degradation of Rhodamine 6G, which comprehensively reflect the characteristics of photocatalytic materials.98 Functionalized with the linker substitution, aminosubstituted MOFs display a definitely different effect on the unsubstituted ones (Figure 20). Both of the activity of MIL-

Figure 21. Schematic diagrams of photogenerated hole oxidation of alcohols with the cancellation of electron though CCl4. Reprinted with permission from ref 51. Copyright 2016 Elsevier.

5. STABILITY 5.1. Self-Decomposition. The instability of MOFs can be directly seen in the previous section of synthesis, especially for the preparation of MIL-53(Fe), MIL-88B(Fe), and MIL101(Fe) crystals, the interaction of metal center and organic ligand is not stronger enough.49 The collapse of the basic structure would contribute to a loss of fundamental function, which we defined as self-decomposition. As the inset image of Figures 4 and 5, a complex interlaced structure might have been a possible strategy for the prevention of self-decomposition, showing in a higher purity product with stable structure. In addition, as shown in Figures 6, 8, 9, 10, and 13, the selfdecomposition of combined structure occurred more frequently, leading a meaningless introduction of distinctive composite. Generally, the recyclability and recycle time were adopted to infer the possibility of self-decomposition by evaluating magnetism, SSA, and catalytic performance. Practically, these methods under the remediation of various environments are more convincing than the theoretical research for the multifunctional MOFs. 5.2. Dissolution. The remediation of dissolved pollution requires that the iron containing MOFs have low dissolution, showing in the enhancement of well-defined crystallization to the efficiency of photocatalysis.34 The crucial property is also called water stability because of the existence of moisture and water in most cases.99 The mentioned Figures 3 and 7 provided the SEM image of regular crystallinity, and DMF was the common solvent for shaping. The stability under fluoride-free conditions is more appealing with the investigation on the effect of pH and temperature. Bezverkhyy et al. suggested that the decrease in BET surface area and the generation of α-Fe2O3 nanoparticles indicate the partial degradation of MIL-53(Fe) and MIL-100(Fe), resulting in a poor crystallinity.45 The instability for the typical MILs with Fe content in acidic conditions was considered as the bottleneck of the wider application. Nevertheless, it is noteworthy that the UiO-66 possessed the possibility of long-term running for remarkable

Figure 20. Degradation of Rhodamine 6G over MIL-88B(Fe), MIL100(Fe), NH2-MIL-101(Fe), NH2-MIL-88B(Fe), and Fe(III)-aminogel at selected wavelengths. Reprinted with permission from ref 98. Copyright 2013 American Chemical Society.

101(Fe) and MIL-88B(Fe) were higher before aminosubstituted. Interestingly, the chemical composition of aminosubstituted MIL-101(Fe) with amorphous gel, namely Fe(III)aminogel, possessed a higher photocatalytic activity and stability than its crystalline analogue. Meanwhile, Xu et al. also evaluate the degradation efficiency of MIL-88B(Fe) for RhB and MB under visible light though hole-oxidation.84 The image of SEM and TEM accurately describe the spindlelike MIL-88B(Fe) with uniform size of 195 nm in width and 385 nm in length. In the latest research, Yang et al. investigated the selective oxidation of alcohols to ketones or aldehydes via three20271


Review


Fortunately, several sophisticated and practical strategies have been proposed for the above challenge as the reference and tendency. (1) Microwave and ultrasonic have been adopted to the enhancement of MILs (e.g., MIL-88B(Fe), NH2-MIL88B(Fe), M@MIL-100(Fe), Fe 3 O 4 @MIL-100(Fe), and Fe3O4@MIL-101(Fe)), accelerating the synthesis time obviously. (2) FexCo3−xO4 nanocages without organic ligand derived from iron containing MOFs possessed a hollow structure, denoting a more stable structure and higher efficiency. (3) Hybrid materials and core−shell structure introduced the magnetism for the convenient recycle. (4) Several suitable electron and hole scavengers were used for the elimination of negative effect in the degradation process.51,96 (5) The cytotoxicity assessment of ROS for the HepG2 cell incubation develops an practical approach to evaluate the potential risk of radicals to human body.82

hydrostability across a wide pH range and high rate of adsorptive removal of organic acid for the strong π−π interactions, indicating a combined method for the improvement of MILs.61 5.3. Reaction with Medium. Iron-containing MOFs are regarded as both efficient semiconductor and catalyst, and the generation of the intermediates would cause no damage to the structure.31 Meanwhile, the chemisorption that caused the distorted geometry of iron sites for the uptake of toxic gas could be reversible.74 The ligands in MOFs are similar to the organic contamination, and it would consume active ingredients in the medium. Furthermore, it could be impossible to recover its previous structure for the unexpected transformation. For instance, the cyanide catalyst of [Co(CN)6]3− in the Fe−Co PBAs have excellent catalytic activity, CN− in the bulk solution would reduce oxidants. The stability of Fe−Co PBAs might prefer to be affected by the change of CN−, and the nanocages were proposed to overcome it attributed to the removal of CN−.23

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Tel: +86 731 84673567.

6. CONCLUSION AND PERSPECTIVES Iron-containing MOFs have great vitality for the environmental restoration as multifunctional and high performance nanomaterials. The novel structure design and traditional MILs synthesis have been summarized, aiming at a more extensive and stable products for adsorption and catalytic degradation. In addition, the effect on the distorted Fe site, CUS and OMSs can be exploited deeply while a better understanding of mechanism for the reduction over photoinduced electron as well as the oxidation with •OH, SO4•−, and photoinduced hole might attribute to the catalytic efficiency. After comparing present studies, we try to figure out ways to unravel the difficulties for the further development of industrialization. MOFs with Fe content have infiltrated into almost every aspect of environmental remediation, but it still remains challenging in the following four aspects. (a) Synthesis: Solvothermal synthesis is one of the most important methods for the fabrication of MOF or MOF-based materials, and both of the time and energy consumption hinder the potential for a pilot-scale application. The lack of optimized size, purity, and crystallinity for the specific field of environment even with identical initial solution are not the suitable parameters for novel ligands. (b) Stability: The water stability and recycle time are essential for the actual working place, and the capacity of some highly efficient iron-containing MOFs would sharply decrease at the second time. The organic ligands present have the risk of being destroyed by additional oxidants, indicating a lower stability and unnecessary loss. (c) Mechanism: The short of theoretical-calculation-directed studies limited the further research for both of the charge balance for the stability and the DFT for the adsorption are not accepted widely.32,70 The precise pathway goes beyond specific radicals or intermediates for the degradation process have not been achieving a unique relationship with catalyst for a higher efficiency. (d) Toxicity: The security risks are inconspicuous in the whole degradation procedures in the aqueous environment. On the one hand, MOFs, its degradation outcomes caused by low stability and the residual solvent (e.g., DMF, hydrofluoric acid and nitric acid) remain a concern. On the other hand, the toxicity of solution after the treatment of photocatalysis or heterogeneous catalysis, the numerous intermediates and the excess radicals with oxidation (e.g., singlet oxygen and ROS) require enough evaluation.

ORCID

Yaoyu Zhou: 0000-0002-8995-6804 Lin Tang: 0000-0001-6996-7955 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS The study was financially supported by the National Program for Support of Top−Notch Young Professionals of China (2012), Projects 51222805, 51579096, 51521006, and 51508175 supported by National Natural Science Foundation of China, and the Program for New Century Excellent Talents in University from the Ministry of Education of China (NCET11-0129)

■

REFERENCES

(1) Wang, H.; Yuan, X.; Wu, Y.; Zeng, G.; Chen, X.; Leng, L.; Li, H. Synthesis and Applications of Novel Graphitic Carbon Nitride/metalorganic Frameworks Mesoporous Photocatalyst for Dyes Removal. Appl. Catal., B 2015, 174−175, 445−454. (2) Zhou, W.; Guo, L. Iron Triad (Fe, Co, Ni) Nanomaterials: Structural Design, Functionalization and Their Applications. Chem. Soc. Rev. 2015, 44, 6697−6707. (3) Horcajada, P.; Chalati, T.; Serre, C.; Gillet, B.; Sebrie, C.; Baati, T.; Eubank, J. F.; Heurtaux, D.; Clayette, P.; Kreuz, C.; et al. Porous Metal-organic Framework Nanoscale Carriers as a Potential Platform for Drug Delivery and Imaging. Nat. Mater. 2010, 9, 172−178. (4) Taylor-Pashow, K. M.; Della Rocca, J.; Xie, Z.; Tran, S.; Lin, W. Postsynthetic Modifications of Iron-carboxylate Nanoscale Metalorganic Frameworks for Imaging and Drug Delivery. J. Am. Chem. Soc. 2009, 131, 14261−14263. (5) Zhang, L.; Wu, H. B.; Xu, R.; Lou, X. W. Porous Fe2O3 Nanocubes Derived from MOFs for Highly Reversible Lithium Storage. CrystEngComm 2013, 15, 9332−9335. (6) Kim, W.; Mcclure, B. A.; Edri, E.; Frei, H. Coupling Carbon Dioxide Reduction with Water Oxidation in Nanoscale Photocatalytic Assemblies. Chem. Soc. Rev. 2016, 45, 3221−3243. (7) Sun, C.; Dong, Q.; Yang, J.; Dai, Z.; Lin, J.; Chen, P.; Huang, W.; Dong, X. Metal-organic framework derived CoSe2 nanoparticles anchored on carbon fibers as bifunctional electrocatalysts for efficient overall water splitting. Nano Res. 2016, 9, 2234−2243. (8) Chi, L.; Xu, Q.; Liang, X.; Wang, J.; Su, X. Iron-Based Metal− Organic Frameworks as Catalysts for Visible Light-Driven Water Oxidation. Small 2016, 12, 1351−1358. 20272


Review


crossover Coordination Polymer. Angew. Chem., Int. Ed. 2009, 48, 8944−8947. (26) Reed, D. A.; Xiao, D. J.; Gonzalez, M. I.; Darago, L. E.; Herm, Z. R.; Grandjean, F.; Long, J. R. Reversible CO Scavenging via AdsorbateDependent Spin State Transitions in an Iron(II)-Triazolate Metalorganic Framework. J. Am. Chem. Soc. 2016, 138, 5594−5602. (27) Etaiw, E. D. H.; El-Bendary, M. M. Degradation of Methylene Blue by Catalytic and Photo-catalytic Processes Catalyzed by the Organotin-polymer3∞[(Me3Sn)4Fe(CN)6]. Appl. Catal., B 2012, 126, 326−333. (28) Zhang, C. F.; Qiu, L. G.; Ke, F.; Zhu, Y. J.; Yuan, Y. P.; Xu, G. S.; Jiang, X. A Novel Magnetic Recyclable Photocatalyst Based on a Core-shell Metal-organic Framework Fe3O4@MIL-100(Fe) for the Decolorization of Methylene Blue Dye. J. Mater. Chem. A 2013, 1, 14329−14334. (29) Zhao, H.; Qian, L.; Lv, H.; Wang, Y.; Zhao, G. Introduction of a Fe3O4 Core Enhances the Photocatalytic Activity of MIL-100(Fe) with Tunable Shell Thickness in the Presence of H2O2. ChemCatChem 2015, 7, 4148−4155. (30) Yue, X.; Guo, W.; Li, X. Core-shell Fe3O4@MIL-101(Fe) Composites as Heterogeneous Catalysts of Persulfate Activation for the Removal of Acid Orange 7. Environ. Sci. Pollut. Res. 2016, 23, 15218−15226. (31) Wang, H. H.; Yang, J.; Liu, Y. Y.; Song, S.; Ma, J. F. Heterotrimetallic Organic Framework Assembled with FeIII/BaII/NaI and Schiff Base: Structure and Visible Photocatalytic Degradation of Chlorophenols. Cryst. Growth Des. 2015, 15, 4986−4992. (32) Chen, Z.; Ling, L.; Wang, B.; Fan, H.; Shangguan, J.; Mi, J. Adsorptive Desulfurization with Metal-organic Frameworks: A Density Functional Theory Investigation. Appl. Surf. Sci. 2016, 387, 483−490. (33) Shi, L.; Wang, T.; Zhang, H.; Chang, K.; Meng, X.; Liu, H.; Ye, J. An Amine-Functionalized Iron(III) Metal-organic Framework as Efficient Visible-Light Photocatalyst for Cr(VI) Reduction. Adv. Sci. 2015, 2, 1500006. (34) Dimitrova, D. G. Iron Based Metal Organic Frameworks as Photocatalysts for Chromium (VI) Degradation. Bachelor Thesis, University College Utrecht, Utrecht, The Netherlands, 2015. (35) Liang, R.; Jing, F.; Shen, L.; Qin, N.; Wu, L. MIL-53(Fe) as a Highly Efficient Bifunctional Photocatalyst for the Simultaneous Reduction of Cr(VI) and Oxidation of Dyes. J. Hazard. Mater. 2015, 287, 364−372. (36) Liang, R.; Jing, F.; Shen, L.; Qin, N.; Wu, L. M@MIL-100(Fe) (M = Au, Pd, Pt) Nanocomposites Fabricated by a Facile Photodeposition Process: Efficient Visible-light Photocatalysts for Redox Reactions in Water. Nano Res. 2015, 8, 3237−3249. (37) Hasan, Z.; Jhung, S. H. A Facile Method to Disperse NonPorous Metal Organic Frameworks: Composite Formation with a Porous Metal Organic Framework and Application in Adsorptive Desulfurization. ACS Appl. Mater. Interfaces 2015, 7, 10429−10435. (38) Zhang, L.; Wu, H. B.; Lou, X. W. Metal-organic-rameworksderived General Formation of Hollow Structures with High Complexity. J. Am. Chem. Soc. 2013, 135, 10664−10672. (39) Zhang, Z.; Chen, Y.; Xu, X.; Zhang, J.; Xiang, G.; He, W.; Wang, X. Well-defined Metal-organic Framework Hollow Nanocages. Angew. Chem., Int. Ed. 2014, 53, 429−433. (40) Li, Y.; Liu, H.; Li, W. J.; Zhao, F. Y.; Ruan, W. J. A Nanoscale Fe(II) Metal−Organic Framework with a Bipyridinedicarboxylate Ligand as a High Performance Heterogeneous Fenton Catalyst. RSC Adv. 2016, 6, 6756−6760. (41) Li, J.; Yang, J.; Liu, Y. Y.; Ma, J.-F. Two Heterometallic-organic Frameworks Composed of Iron(III)-Salen-Based Ligands and d 10 Metals: Gas Sorption and Visible-Light Photocatalytic Degradation of 2-Chlorophenol. Chem. - Eur. J. 2015, 21, 4413−4421. (42) Zhao, H.; Qian, L.; Lv, H.; Wang, Y.; Zhao, G. Introduction of a Fe3O4 Core Enhances the Photocatalytic Activity of MIL-100(Fe) with Tunable Shell Thickness in the Presence of H2O2. ChemCatChem 2015, 7, 4148−4155. (43) Yue, X.; Guo, W.; Li, X.; Zhou, H.; Wang, R. Core-shell Fe3O4 @MIL-101(Fe) Composites as Heterogeneous Catalysts of Persulfate

(9) Manna, K.; Zhang, T.; Carboni, M.; Abney, C. W.; Lin, W. Salicylaldimine-based Metal-organic Framework Enabling Highly Active Olefin Hydrogenation with Iron and Cobalt Catalysts. J. Am. Chem. Soc. 2014, 136, 13182−13185. (10) Singh, M. K.; Bandyopadhyay, D. Nanoporous Iron(III) Porphyrin Frameworks: an Efficient Catalyst for [4 + 2] Cycloaddition Reactions of Unactivated Aldehydes with a Diene. New J. Chem. 2016, 40, 6358−6363. (11) Nguyen, V. T.; Ngo, H. Q.; Le, D. T.; Truong, T.; Phan, N. T. S. Iron-catalyzed Domino Sequences: One-pot Oxidative Synthesis of Quinazolinones Using Metal−organic Framework Fe3O(BPDC)3 as an Efficient Heterogeneous Catalyst. Chem. Eng. J. 2016, 284, 778− 785. (12) Colinas, I. R.; Silva, R. C.; Oliver, S. R. Reversible, Selective Trapping of Perchlorate from Water in Record Capacity by a Cationic Metal-organic Framework. Environ. Sci. Technol. 2016, 50, 1949−1954. (13) Vellingiri, K.; Kumar, P.; Kim, K. H. Coordination Polymers: Challenges and Future Scenarios for Capture and Degradation of Volatile Organic Compounds. Nano Res. 2016, 9, 3181−3208. (14) Dias, E. M.; Petit, C. Towards the Use of Metal-organic Frameworks for Water Reuse: a Review of the Recent Advances in the Field of Organic Pollutants Removal and Degradation and the Next Steps in the Field. J. Mater. Chem. A 2015, 3, 22484−22506. (15) Bachman, J. E.; Smith, Z. P.; Li, T.; Xu, T.; Long, J. R. Enhanced Ethylene Separation and Plasticization Resistance in Polymer Membranes Incorporating Metal-organic Framework Nanocrystals. Nat. Mater. 2016, 15, 845−849. (16) Ai, L.; Zhang, C.; Li, L.; Jiang, J. Iron Terephthalate Metalorganic Framework: Revealing the Effective Activation of Hydrogen Peroxide for the Degradation of Organic Dye Under Visible Light Irradiation. Appl. Catal., B 2014, 148−149, 191−200. (17) Zhang, C.; Ai, L.; Jiang, J. Solvothermal Synthesis of MIL53(Fe) Hybrid Magnetic Composites for Photoelectrochemical Water Oxidation and Organic Pollutant Photodegradation Under Visible Light. J. Mater. Chem. A 2015, 3, 3074−3081. (18) Zhou, T.; Du, Y.; Yin, S.; Tian, X.; Yang, H.; Wang, X.; Liu, B.; Zheng, H.; Qiao, S.; Xu, R. Nitrogen-doped Cobalt Phosphate@ nanocarbon Hybrids for Efficient Electrocatalytic Oxygen Reduction. Energy Environ. Sci. 2016, 9, 2563−2570. (19) Jia, Q.; Ramaswamy, N.; Tylus, U.; Strickland, K.; Li, J.; Serov, A.; Artyushkova, K.; Atanassov, P.; Anibal, J.; Gumeci, C.; et al. Spectroscopic Insights into the Nature of Active Sites in IronNitrogen-Carbon Electrocatalysts for Oxygen Reduction in Acid and the Redox Mechanisms. Nano Energy 2016, 29, 65−82. (20) Sun, Q.; Liu, M.; Li, K.; Zuo, Y.; Han, Y.; Wang, J.; Song, C.; Zhang, G.; Guo, X. Facile Synthesis of Fe-containing Metal-organic Frameworks as Highly Efficient Catalysts for Degradation of Phenol at Neutral pH and Ambient Temperature. CrystEngComm 2015, 17, 7160−7168. (21) Lv, H.; Zhao, H.; Cao, T.; Qian, L.; Wang, Y.; Zhao, G. Efficient Degradation of High Concentration Azo-dye Wastewater by Heterogeneous Fenton Process with Iron-based Metal-organic Framework. J. Mol. Catal. A: Chem. 2015, 400, 81−89. (22) Qiao, S.; Min, L.; Li, K.; Han, Y.; Yi, Z.; Wang, J.; Song, C.; Zhang, G.; Guo, X.; Qiao, S. Controlled Synthesis of Mixed-valent Fecontaining Metal Organic Frameworks for the Degradation of Phenol Under Mild Conditions. Dalton Trans. 2016, 45, 7952−7959. (23) Li, X.; Wang, Z.; Zhang, B.; Rykov, A. I.; Ahmed, M. A.; Wang, J. FexCo3−xO4 Nanocages Derived from Nanoscale Metal-organic Frameworks for Removal of Bisphenol A by Activation of Peroxymonosulfate. Appl. Catal., B 2016, 181, 788−799. (24) Li, X.; Liu, J.; Rykov, A. I.; Han, H.; Jin, C.; Liu, X.; Wang, J. Excellent Photo-Fenton Catalysts of Fe−Co Prussian Blue Analogues and Their Reaction Mechanism Study. Appl. Catal., B 2015, 179, 196− 205. (25) Agustí, G.; Ohtani, R.; Yoneda, K.; Gaspar, A. B.; Ohba, M.; Sánchezroyo, J. F.; Muñoz, M. C.; Kitagawa, S.; Real, J. A. Oxidative Addition of Halogens on Open Metal Sites in a Microporous Spin20273


Review

ACS Applied Materials & Interfaces Activation for the Removal of Acid Orange 7. Environ. Sci. Pollut. Res. 2016, 23, 15218−15226. (44) Liang, R.; Luo, S.; Jing, F.; Shen, L.; Qin, N.; Wu, L. A simple Strategy for Fabrication of Pd@MIL-100(Fe) Nanocomposite as a Visible-light-driven Photocatalyst for the Treatment of Pharmaceuticals and Personal Care Products (PPCPs). Appl. Catal., B 2015, 176− 177, 240−248. (45) Bezverkhyy, I.; Weber, G.; Bellat, J. P. Degradation of Fluoridefree MIL-100(Fe) and MIL-53(Fe) in Water: Effect of Temperature and pH. Microporous Mesoporous Mater. 2016, 219, 117−124. (46) Garcia Marquez, A.; Horcajada, P.; Grosso, D.; Ferey, G.; Serre, C.; Sanchez, C.; Boissiere, C. Green Scalable Aerosol Synthesis of Porous Metal-organic Frameworks. Chem. Commun. 2013, 49, 3848− 3850. (47) Haque, E.; Khan, N. A.; Park, J. H.; Jhung, S. H. Synthesis of a Metal–Organic Framework Material, Iron Terephthalate, by Ultrasound, Microwave, and Conventional Electric Heating: A Kinetic Study. Chem. - Eur. J. 2010, 16, 1046−1052. (48) Halper, S. R.; Do, L.; Stork, J. R.; Cohen, S. M. Topological Control in Heterometallic Metal-organic Frameworks by Anion Templating and Metalloligand Design. J. Am. Chem. Soc. 2006, 128, 15255−15268. (49) Ma, M.; Bétard, A.; Weber, I.; AlHokbany, N. S.; Fischer, R. A.; MetzlerNolte, N. Iron-Based Metal-organic Frameworks MIL-88B and NH2-MIL-88B: High Quality Microwave Synthesis and SolventInduced Lattice “Breathing. Cryst. Growth Des. 2013, 13, 2286−2291. (50) Ma, M.; Noei, H.; Mienert, B.; Niesel, J.; Bill, E.; Muhler, M.; Fischer, R. A.; Wang, Y.; Schatzschneider, U.; Metzler-Nolte, N. Iron Metal-organic Frameworks MIL-88B and NH2 -MIL-88B for the Loading and Delivery of the Gasotransmitter Carbon Monoxide. Chem. - Eur. J. 2013, 19, 6785−6790. (51) Yang, Z.; Xu, X.; Liang, X.; Lei, C.; Wei, Y.; He, P.; Lv, B.; Ma, H.; Lei, Z. MIL-53(Fe)-graphene Nanocomposites: Efficient Visiblelight Photocatalysts for the Selective Oxidation of Alcohols. Appl. Catal., B 2016, 198, 112−123. (52) Zhang, Y.; Tao, C. A.; Song, J.; Wang, J. Metal-organic Frameworks/Graphene Oxide Composites: Preparation and Applications in Dye Absorption. 4th ICSEEE 2015, 642−645. (53) Petit, C.; Bandosz, T. J. Synthesis, Characterization, and Ammonia Adsorption Properties of Mesoporous Metal−Organic Framework (MIL(Fe))-Graphite Oxide Composites: Exploring the Limits of Materials Fabrication. Adv. Funct. Mater. 2011, 21, 2108− 2117. (54) Jin, Z.; Dong, W.; Yang, M.; Wang, J.; Gao, H.; Wang, G. Onepot Preparation of Hierarchical Nanosheet-Constructed Fe3O4/MIL88B(Fe) Magnetic Microspheres with High Efficiency Photocatalytic Degradation of Dye. ChemCatChem 2016, 8, 3510−3517. (55) Deleu, W. P. R.; Rivero, G.; Teixeira, R. F.; Du Prez, F. E. D.; De Vos, D. E. D. MOFs Encapsulated in Photocleavable Capsules for UV-light Triggered Catalysis. Chem. Mater. 2015, 27, 5495−5502. (56) Kim, S. I.; Yoon, T. U.; Kim, M. B.; Lee, S. J.; Hwang, Y. K.; Chang, J. S.; Kim, H. J.; Lee, H. N.; Lee, U. H.; Bae, Y. S. Metalorganic Frameworks with High Working Capacities and Cyclic Hydrothermal Stabilities for Fresh Water Production. Chem. Eng. J. 2016, 286, 467−475. (57) Jeremias, F.; Khutia, A.; Henninger, S. K.; Janiak, C. MIL100(Al, Fe) as Water Adsorbents for Heat Transformation Purposes a Promising Application. J. Mater. Chem. 2012, 22, 10148−10151. (58) Ke, F.; Luo, G.; Chen, P.; Jiang, J.; Yuan, Q.; Cai, H.; Peng, C.; Wan, X. Porous Metal-organic Frameworks Adsorbents as a Potential Platform for Defluoridation of Water. J. Porous Mater. 2016, 23, 1065− 1073. (59) Lan, X.; Zhang, H.; Bai, P.; Guo, X. Investigation of Metal Organic Frameworks for the Adsorptive Removal of Hydrochloride from Dilute Aqueous Solution. Microporous Mesoporous Mater. 2016, 231, 40−46. (60) Li, Y. X.; Jiang, W. J.; Tan, P.; Liu, X. Q.; Zhang, D. Y.; Sun, L. B. What Matters to the Adsorptive Desulfurization Performance of Metal-Organic Frameworks? J. Phys. Chem. C 2015, 119, 21969.

(61) Zhang, H.; Lan, X.; Bai, P.; Guo, X. Adsorptive Removal of Acetic Acid from Water with Metal-organic Frameworks. Chem. Eng. Res. Des. 2016, 111, 127−137. (62) Tong, M.; Liu, D.; Yang, Q.; Devautourvinot, S.; Maurin, G.; Zhong, C. Influence of Framework Metal Ions on the Dye Capture Behavior of MIL-100 (Fe, Cr) MOF Type Solids. J. Mater. Chem. A 2013, 1, 8534−8537. (63) Hasan, Z.; Jhung, S. H. Removal of Hazardous Organics from Water Using Metal-organic Frameworks (MOFs): Plausible Mechanisms for Selective Adsorptions. J. Hazard. Mater. 2015, 283, 329− 339. (64) Haque, E.; Jun, J. W.; Jhung, S. H. Adsorptive Removal of Methyl Orange and Methylene Blue from Aqueous Solution with a Metal-organic Framework Material, Iron Terephthalate (MOF-235). J. Hazard. Mater. 2011, 185, 507−511. (65) Ma, N. Adsorptive Removal of Acid Orange 7 from Aqueous Solution with Metal-organic Framework Material, Iron (III) Trimesate. Water, Air, Soil Pollut. 2014, 225, 1956. (66) Lan, H.; Li, J.; Meng, S.; An, X.; Hu, C.; Liu, R.; Liu, H.; Qu, J. Efficient Conversion of Dimethylarsinate into Arsenic and its Simultaneous Adsorption Removal over FeCx/N-doped Carbon Fiber Composite in an Electro-Fenton Process. Water Res. 2016, 100, 57−64. (67) Jun, J. W.; Tong, M.; Jung, B. K.; Hasan, Z.; Zhong, C.; Jhung, S. H. Effect of Central Metal Ions of Analogous Metal-organic Frameworks on Adsorption of Organoarsenic Compounds from Water: Plausible Mechanism of Adsorption and Water Purification. Chem. - Eur. J. 2015, 21, 347−354. (68) Barea, E. Toxic gas removal − Metal−organic Frameworks for the Capture and Degradation of Toxic Gases and Vapours. Chem. Soc. Rev. 2014, 43, 5419−5430. (69) Bhadra, B. N.; Jhung, S. H. Selective Adsorption of n-Alkanes from n-Octane on Metal-Organic Frameworks: Length Selectivity. ACS Appl. Mater. Interfaces 2016, 8, 6770−6777. (70) Wu, Y.; Chen, H.; Xiao, J.; Liu, D.; Liu, Z.; Qian, Y.; Xi, H. Adsorptive Separation of Methanol-acetone on Isostructural Series of Metal-organic Frameworks M-BTC (M = Ti, Fe, Cu, Co, Ru, Mo): A Computational Study of Adsorption Mechanisms and Metalsubstitution Impacts. ACS Appl. Mater. Interfaces 2015, 7, 26930− 26940. (71) Schauer, J. J.; Fraser, M. P.; Cass, G. R.; Simoneit, B. R. Source Reconciliation of Atmospheric Gas-phase and Particle-phase Pollutants during a Severe Photochemical Smog Episode. Environ. Sci. Technol. 2002, 36, 3806−3814. (72) Petit, C.; Bandosz, T. J. Exploring the Coordination Chemistry of MOF-graphite Oxide Composites and Their Applications as Adsorbents. Dalton Trans. 2012, 41, 4027−4035. (73) Mckinlay, A. C.; Eubank, J. F.; Wuttke, S.; Xiao, B.; Wheatley, P. S.; Bazin, P.; Lavalley, J. C.; Daturi, M.; Vimont, A.; Weireld, G. D.; et al. Nitric Oxide Adsorption and Delivery in Flexible MIL-88(Fe) Metal-organic Frameworks. Chem. Mater. 2013, 25, 1592−1599. (74) Reed, D. A.; Xiao, D. J.; Gonzalez, M. I.; Darago, L. E.; Herm, Z. R.; Grandjean, F.; Long, J. R. Reversible CO Scavenging via AdsorbateDependent Spin State Transitions in an Iron(II)-Triazolate Metalorganic Framework. J. Am. Chem. Soc. 2016, 138, 5594−5602. (75) Deng, Y.; Englehardt, J. D. Treatment of Landfill Leachate by the Fenton Process. Water Res. 2006, 40, 3683−3694. (76) Navalon, S.; Alvaro, M.; Garcia, H. Heterogeneous Fenton Catalysts Based on Clays, Silicas and Zeolites. Appl. Catal., B 2010, 99, 1−26. (77) Herney-Ramirez, J.; Vicente, M. A.; Madeira, L. M. Heterogeneous Photo-Fenton Oxidation with Pillared Clay-based Catalysts for Wastewater Treatment: A review. Appl. Catal., B 2010, 98, 10−26. (78) Giannakis, S.; Polo López, M. I.; Spuhler, D.; Sanchez Pérez, J. A.; Fernandez Ibáñez, P.; Pulgarin, C. Solar Disinfection is an Augmentable, in Situ-generated Photo-Fenton ReactionPart 1: A Review of the Mechanisms and the Fundamental Aspects of the Process. Appl. Catal., B 2016, 199, 199−223. 20274


Review

ACS Applied Materials & Interfaces (79) Giannakis, S.; López, M. I. P.; Spuhler, D.; Pérez, J. A. S.; Ibáñez, P. F.; Pulgarin, C. Solar Disinfection is an Augmentable, in Situgenerated Photo-Fenton ReactionPart 2: A Review of the Applications for Drinking Water and Wastewater Disinfection. Appl. Catal., B 2016, 198, 431−446. (80) Brillas, E.; Sirés, I.; Oturan, M. A. Electro-Fenton Process and Related Electrochemical Technologies Based on Fenton’s Reaction Chemistry. Chem. Rev. 2009, 109, 6570−6631. (81) Sun, Q.; Liu, M.; Li, K.; Han, Y.; Zuo, Y.; Wang, J.; Song, C.; Zhang, G.; Guo, X. Controlled Synthesis of Mixed-valent Fecontaining Metal Organic Frameworks for the Degradation of Phenol Under Mild Conditions. Dalton Trans. 2016, 45, 7952−7959. (82) Liu, K.; Gao, Y.; Liu, J.; Wen, Y.; Zhao, Y.; Zhang, K.; Yu, G. Photoreactivity of Metal-organic Frameworks in Aqueous Solutions: Metal Dependence of Reactive Oxygen Species Production. Environ. Sci. Technol. 2016, 50, 3634−3640. (83) Zhang, Z.; Li, X.; Liu, B.; Zhao, Q.; Chen, G. Hexagonal Microspindle of NH2-MIL-101(Fe) Metal-organic Frameworks with Visible-light-induced Photocatalytic Activity for the Degradation of Toluene. RSC Adv. 2016, 6, 4289−4295. (84) Xu, B.; Yang, H.; Cai, Y.; Yang, H.; Li, C. Preparation and Photocatalytic Property of Spindle-like MIL-88B(Fe) Nanoparticles. Inorg. Chem. Commun. 2016, 67, 29−31. (85) Wang, D.; Wang, M.; Li, Z. Fe-based Metal-organic Frameworks (MOFs) for Highly Selective Photocatalytic Benzene Hydroxylation to Phenol. ACS Catal. 2015, 5, 6852−6857. (86) Ai, L.; Zhang, C.; Li, L.; Jiang, J. Iron Terephthalate Metalorganic framework: Revealing the Effective Activation of Hydrogen Peroxide for the Degradation of Organic Dye Under Visible Light Irradiation. Appl. Catal., B 2014, 148−149, 191−200. (87) Li, H.; Wan, J.; Ma, Y.; Yan, W.; Xi, C.; Guan, Z. Degradation of Refractory Dibutyl Phthalate by Peroxymonosulfate Activated with Novel Catalysts Cobalt Metal-organic Frameworks: Mechanism, Performance, and Stability. J. Hazard. Mater. 2016, 318, 154−163. (88) Kim, K.; Qiu, P.; Cui, M.; Khim, J. Development and Application of Fe3O4−Pd Nanospheres as Catalyst for Electrochemical-heterogeneous Fenton Process. Chem. Eng. J. 2016, 284, 1165−1173. (89) Liang, R.; Jing, F.; Shen, L.; Qin, N.; Wu, L. M@MIL-100(Fe) (M = Au, Pd, Pt) Nanocomposites Fabricated by a Facile Photodeposition Process: Efficient Visible-light Photocatalysts for Redox Reactions in Water. Nano Res. 2015, 8, 3237−3249. (90) Zhao, H.; Chen, Y.; Peng, Q.; Wang, Q.; Zhao, G. Catalytic Activity of MOF(2Fe/Co)/carbon Aerogel for Improving H2O2 and · OH Generation in Solar Photo−electro−Fenton Process. Appl. Catal., B 2017, 203, 127−137. (91) Hu, P.; Long, M. Cobalt-catalyzed Sulfate Radical-based Advanced Oxidation: A Review on Heterogeneous Catalysts and Applications. Appl. Catal., B 2016, 181, 103−117. (92) Gao, Y.; Li, S.; Li, Y.; Yao, L.; Zhang, H. Accelerated Photocatalytic Degradation of Organic Pollutant over Metal-organic Framework MIL-53(Fe) Under Visible LED Light Mediated by Persulfate. Appl. Catal., B 2017, 202, 165−174. (93) Li, X.; Guo, W.; Liu, Z.; Wang, R.; Liu, H. Fe-based MOFs for Efficient Adsorption and Degradation of Acid Orange 7 in Aqueous Solution via Persulfate Activation. Appl. Surf. Sci. 2016, 369, 130−136. (94) Qin, F. X.; Jia, S. Y.; Liu, Y.; Han, X.; Ren, H. T.; Zhang, W. W.; Hou, J. W.; Wu, S. H. Metal-organic Framework as a Template for Synthesis of Magnetic CoFe2O4 Nanocomposites for Phenol Degradation. Mater. Lett. 2013, 101, 93−95. (95) Lin, K. Y. A.; Hsu, F. K. Magnetic Iron/Carbon Nanorod Derived from Metal Organic Framework as an Efficient Heterogeneous Catalyst for Chemical Oxidation Process in Water. RSC Adv. 2015, 5, 50790−50800. (96) Liang, R.; Jing, F.; Shen, L.; Qin, N.; Wu, L. MIL-53(Fe) as a Highly Efficient Bifunctional Photocatalyst for the Simultaneous Reduction of Cr(VI) and Oxidation of Dyes. J. Hazard. Mater. 2015, 287, 364−372.

(97) Xiong, Y. Y.; Li, J. Q.; Yan, C. S.; Gao, H. Y.; Zhou, J. P.; Gong, L. L.; Luo, M. B.; Zhang, L.; Meng, P. P.; Luo, F. MOF Catalysis of Fe(II)-to-Fe(III) Reaction for an Ultrafast and One-step Generation of the Fe2O3@MOF Composite and Uranium(vi) Reduction by Iron(ii) Under Ambient Conditions. Chem. Commun. 2016, 52, 9538−9541. (98) Laurier, K. G.; Vermoortele, F.; Ameloot, R.; De Vos, D. E.; Hofkens, J.; Roeffaers, M. B. Iron(III)-based Metal-organic Frameworks as Visible Light Photocatalysts. J. Am. Chem. Soc. 2013, 135, 14488−14491. (99) Wang, C.; Liu, X.; Keser Demir, N.; Chen, J. P.; Li, K. Applications of Water Stable Metal-organic Frameworks. Chem. Soc. Rev. 2016, 45, 5107−5134. (100) Janiak, C.; Vieth, J. K. MOFs, MILs and More: Concepts, Properties and Applications for Porous Coordination Networks (PCNs). New J. Chem. 2010, 34, 2366. (101) Qin, L.; Li, Z.; Xu, Z.; Guo, X.; Zhang, G. Organic-aciddirected Assembly of Iron-carbon Oxides Nanoparticles on Coordinatively Unsaturated Metal Sites of MIL-101 for Green Photochemical Oxidation. Appl. Catal., B 2015, 179, 500−508.

20275


Iron Containing MetalâOrganic Frameworks - ACS Publications

Recommend Documents

Iron Containing MetalâOrganic Frameworks - ACS Publications