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Flexible Bipyridinium Constructed Porous Frameworks with Superior Broad-Spectrum Adsorption toward Organic Pollutants Cheng Chen, Li-Xuan Cai, Bin Tan, Ya-Jun Zhang, Xiao-Dong Yang, Shen Lin, and Jie Zhang Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b01809 • Publication Date (Web): 22 Feb 2017 Downloaded from http://pubs.acs.org on February 23, 2017
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Flexible Bipyridinium Constructed Porous Frameworks with Superior Broad-Spectrum Adsorption toward Organic Pollutants Cheng Chen,†,§ Li‐Xuan Cai, § Bin Tan, § Ya‐Jun Zhang, § Xiao‐Dong Yang, § Shen Lin*† and Jie Zhang* ‡,§ †
College of Chemistry & Chemical Engineering, Fujian Normal University, Fuzhou, Fujian 350007, P. R. China
‡
MOE Key Laboratory of Cluster Science, Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, P. R. China
§
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, CAS, Fuzhou, Fujian 350002, P. R. China
ABSTRACT: A flexible bipyridinium ligand has been introduced into a series of isomorphous metal‐organic frameworks to yield porous materials with subtriangular 1D channel and cage‐like pore space. The introduction of bipyridinium molecules into the porous frameworks leads to the formation of 1D channel with positively‐charged surface, which shows high affinities to polar molecules such as methanol, ethanol and water vapor. Additionally, the bipyridinium molecules possess conjugated pyridyl rings connected by carbon‐carbon single bond, which can rotate freely to keep twisted or large‐conjugated planar configuration by controlling coordination condition during the self‐assembly process. The cage‐ like pore space formed by these flexible bipyridinium molecules contains arene‐arene stacked pyridyl rings and thus renders abundant π‐π interaction sites for efficient adsorption of benzene and toluene molecules, and is also large enough to accommodate cyclohexane molecules. These metal‐organic frameworks show efficient adsorption for benzene, toluene and cyclohexane molecules through high utilization efficiency of unique pore space, and display rarely broad‐spectrum adsorptivity to various organic pollutants with hydrophilic/hydrophobic, conjugated/non‐conjugated characteristics.
INTRODUCTION The design and construction of functional porous coordination polymers (PCPs) with proper pore shape and size, unique pore surface decoration have aroused significant concern. Recently, using mono‐ or bis‐substituted 4,4'‐bipyridinium derivatives as the building units to gain characteristic porous structures have been successfully applied to gas storage,1‐3 separation4,5 and luminescent sensing.6‐8 Previous researches are focused on the pyridinium‐caused charged organic surfaces with strong polarity (or describe as intrinsic Lewis acidic sites), but seldom pay attention to dynamic motion of the aromatic rings influencing the guest adsorption.5 Pyridyl rings in the 4,4'‐bipyridinium moieties are connected by freely‐rotatable carbon‐carbon single bond, which can be fine‐tuned from non‐coplanar structure to high‐conjugated coplanar conformation by controlling self‐assembly condition. Admittedly, the coplanar bipyridinium moieties are conducive to build an arene‐arene stacking fashion in order to accommodate aromatics. In this paper, we report three isomorphous PCPs [Cd2(pbpy)(bdc)2X2]∙nH2O (H2bdc = 1,4‐benzenedicarboxylic acid; pbpy∙2Cl = 1,1'‐
[1,4‐phenylenebis(methylene)]bis(4,4'‐bipyridinium) dichloride; X = Cl, n = 5 (1); X = Br, n = 8 (2); X = Cl/Br, n = 9 (3)) bearing 4,4'‐bipyridinium functional moieties. Attractively, these PCPs show a triangular pore window and a cage‐like pore space constructed by aromatic rings from the bipyridinium and bdc2 units. The bipyridinium ligands decorate pore walls with sufficient Lewis acidic sites that can serve as sensitive ammonia fluorescent sensors,8 while the halide ions can be applied to adjust the planarity of the bipyridinium moiety. Current research is focused on the characteristic pore spaces with arene‐arene stacking fashions applying to special adsorption of organic pollutants. Benzene, toluene and cyclohexane are the most common contaminants in oil and petroleum hydrocarbon products and industrial pollutants. The search for PCP materials in applications such as the removal of these pollutants from water purification, oil spills or industrial exhausts, hydrocarbon storage and transportation, is a great challenge.9‐11 And, furthermore, the exploitation of versatile materials with broad‐spectrum adsorption towards aromatic and nonaromatic organic pollutants is considerably more challenging. Here we show that the PCP
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materials 1, 2 and 3 are efficient for adsorption of typical aromatic and aliphatic compounds benefitting from high utilization efficiency of their unique pore space. It is generally known that the conventional method to enhance the affinity for aromatic adsorbates in the presence of water or moist air is decorating the channel surface with hydrophobic groups.9 Interestingly, the current functional metal‐ bipyridinium PCP materials possess not only abundant positive charged pore surface, but also freely‐rotatable aromatic moieties that are extensively exposed to the pore surface and allow to adsorb both hydrophilic and hydrophobic compounds, which make them more suitable for the broad‐spectrum adsorption towards various organic pollutants.
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formula was confirmed by element analysis and Energy‐ dispersive X‐ray spectroscopy. Crystal data for 3: C44H32N4O8ClBrCd2; Mr = 1084.90; Triclinic P‐1; a = 9.0410(8), b = 17.9143(15), c = 18.8513(7) Å, = 102.091(5), = 102.348(6), = 102.269(7)°, V = 2808.6(4) Å3; T = 295.87(10) K; Z = 2; Dc = 1.283 g·cm–3; μ (Cu Kα) = 7.701 mm–1; F(000) = 1072; 18416 reflections collected, of which 10103 unique (Rint = 0.0697); GOF = 1.056; R1 = 0.0638 and wR2 = 0.1819 [I > 2(I)].
EXPERIMENTAL SECTION Materials and Physical Measurements. All chemicals were obtained from commercial sources and were of GR/AR grade unless otherwise noted. The IR (KBr pellet) spectra were recorded (400‐4000 cm1 region) on an ABB Bomem MB‐102 FT‐IR spectrometer. Thermogravimetric (TG) analysis was performed on a Mettler‐Toledo TGA/SDTA851e thermal analyzer in a flowing air atmosphere at a heating rate of 10°C min1 from 30 to 800 °C. Energy‐dispersive X‐ray spectroscopy (EDS) measurement was performed on a JSM‐6700F scanning electron microscope. Elemental analysis of C, H and N was performed on a Vario EL III CHNOS elemental analyzer. Powder X‐ray diffraction (PXRD) patterns were recorded on a MiniFlex diffractometer with Cu Kα (λ = 1.5406 Å) at a scan speed of 4° min 1. Vapor‐phase adsorption isotherms were measured with an Intelligent Gravimetric Sorption Analyser IGA100B from the Hiden Corporation. The ASAP 2020 surface‐area analyzer was used to measure the CO2 and H2 isotherms; the samples were degassed at 90 °C for 5 h prior to the measurements being taken. Synthesis and Characterization of Crystal Materials. The details of the synthesis and characterization of compounds 1 and 2 were available in previously published work.8 Synthesis of [Cd2(pbpy)(bdc)2ClBr]∙9H2O 3: H2bdc (20 mg, 0.12 mmol), pbpy∙2Cl (50 mg, 0.1 mmol) and Cd(NO3)2∙4H2O (70 mg, 0.22 mmol) were dissolved in the N,N‐dimethylformamide solution (8 mL) in a Teflon vessel of the hydrothermal bomb, an excess KBr (30 mg, 0.25 mmol) was added to the mixture afterwards and stirred for 30 min. The vessel was sealed, placed in an oven and heated at 90 °C for 2 days, and then allowed to cool slowly to room temperature within 2 days. Bright yellow block crystals (3) were obtained in 72% yield. Elemental analysis calc. for C44H50N4O17ClBrCd2: C, 42.38; H, 4.04; N, 4.49; found: C, 42.12; H, 3.91; N, 4.55 %. X-ray Crystallographic Study. Data collection were performed on an Agilent Diffraction SuperNova dual diffractometer, with Cu Kα radiation (λ = 1.54178 Å) at 295.87(10) K for 3. Absorption corrections were performed using a multi‐ scan method. The structures were solved by direct methods and refined by full‐matrix least‐squares on F2 using the SHELX‐97 program package.12,13 All non‐hydrogen atoms were refined with anisotropic displacement parameters. Hydrogen atoms of the ligands were located by geometrical calculations, and their positions and thermal parameters were fixed during structural refinement. Structure refinement after modification of the data for the water molecules with the SQUEEZE routine of PLATON14 led to better refinement and data convergence. The empirical
Figure 1. (a) The pseudo‐hexagonal ring structure of the single 2D coordination sheet of 1. (b) The 2D pseudoclathrate texture shown in another perspective. (c) The 2D grid‐like network and the extended 3D coordination framework in different perspective. (d) Packing view of the whole network, the extended 1D channel is described as a subtriangular passageway measured through connecting the metal nodes on the hole wall.
RESULTS AND DISCUSSION Crystal Structure Characteristics of Bipyridinium Functionalized PCP Materials. These compounds were obtained in N,N‐dimethylformamide by solvothermal synthesis using programmable temperature control. The phase purity and thermostability were verified by elemental analysis, X‐ray powder diffraction (XRPD), IR, Energy‐dispersive X‐ray spectroscopy, and thermogravimetric analysis (Supporting Information, Figure S1‐S4). Single‐crystal X‐ray diffraction analysis reveals that three complexes are isoreticular. The Cd(II) ion is six‐coordinated and the coordination sphere can be described as distorted octahedral geometry completed by one nitrogen atom, one halide atom and four oxygen atoms, with the Cd–O bond lengths in the range of 2.265–2.453 Å, Cd–Cl/Br bond lengths in the range of 2.427–2.594 Å and Cd–N bond lengths in the range of 2.321–2.361 Å in these structures. Different halogen anions are introduced to
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fine‐tune the coordination environment, chloride ions are employed to coordinate to the metal ions in 1, and bromide ions take the place of chloride ions in 2, while there are both chloride ion and bromide ion coordinated to the metal ions in 3 as described in asymmetric unit, respectively (Supporting Information, Figure S5). In crystals, two flexible pbpy ligands connect four rigid bdc2 anions to construct a hexagonal conformation, while these two ligands join eight bdc2 anions to form a decagonal window‐like unit by coordinating with Cd(II) ions as viewed from another perspective, and the polygon units are respectively expanded into a quasi‐honeycomb structure and pseudoclathrate texture in the two‐ dimensional space through 3‐connected nodes (Figure 1a‐1b). While dissecting the structure characteristic in space, we can find a 2D network built by pbpy ligands, simultaneously the 2D motif is further extended by bdc2 anions into a 3D coordination framework (Figure 1c). These isomorphous frameworks remain a 3‐connected (103) network with the ths (ThSi2‐type) topology,15 and the unique 1D channel is formed after the framework undergoes a quadruple interpenetration, showing a triangular window with the approximate pore size of 11.2 Å × 11.4 Å × 12.6 Å as measured through connecting the metal nodes on the hole wall (Figure 1d).8 A PLATON program analysis suggests that there are about 32% of the crystal volume (removing all guests) in 1, 33% in 2 and 3, respectively,16 which provides sufficient vacancy accessible to guest molecules. Interestingly, the grid‐like network is constituted by two different pbpy ligands (marked as ligand A and ligand B) which own diverse dihedral angles in bipyridinium units (Supporting Information, Figure S6). It is found that the dihedral angles of ligand A show little difference in these isostructural crystals, they keep a non‐coplanar configuration with the twisted angles of 32.6˚ in 1, 31.1˚ in 2 and 32.0˚ in 3. In contrast, the ligand B keeps nearly coplanar configuration with the dihedral angles of 2.9˚ in 1 and 1.8˚ in 2, and an increased dihedral angle of 9.8˚ in compound 3, which demonstrate the structural modulation ability of the coordination anions (Supporting Information, Table S1). The bipyridinium units with controllable dihedral angles may play a role in regulating guest molecules adsorption. Gas Sorption. Gas‐adsorption measurements at 77 K reveal that three materials exhibit significant different adsorption ability to H2. The PCP material 3 exhibits better adsorption capacity to hydrogen (32.6 cm3∙g1, 0.29 wt%) than 2 (20.6 cm3∙g1, 0.18 wt%) and 1 (6.3 cm3∙g1, 0.06 wt%), it is more than a half of the adsorption amount (ca. 0.50 wt%) to the similar metal‐bipyridinium framework with [Zn(1,4‐ ndc)(bcbpy)] skeleton.1 Carbon dioxide adsorption isotherms reveal that the adsorption amount of 3 (26.0 cm3∙g1, 0.51 wt%) is higher than 2 (22.1 cm3∙g1,
0.43 wt%) and 1 (19.2 cm3∙g1, 0.38 wt%) (Supporting Information, Figure S7). The pyridinium struts are aligned to constitute the subtriangular channels whose surface is charge‐decorated to provide effective adsorbate‐adsorbent interaction to capture guest molecules. While these bipyridinium functional PCPs are of little advantage in terms of gas adsorption, it may be attributed to the fact that the relatively large channel cannot adequately accommodate small gas molecules as compared with the same bipyridinium functional skeleton [Zn(1,4‐ndc)(bcbpy)] whose pore cross‐section is recorded as 4.7 Å × 4.1 Å.17
Figure 2. The adsorption isotherms (filled symbols) and desorption isotherms (empty symbols) of different solvent vapors onto framework 1 (a), 2 (b) and 3 (c) at 298 K.
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Organic Vapors Sorption. To further evaluate the adsorption and separation properties of these porous frameworks for different guest molecules, the adsorption isotherms for a series of small molecules were measured based on complex 1, 2 and 3. These compounds were heated at 90 °C under vacuum for 5 h before the analysis, and their activation XRPD patterns (Supporting Information, Figure S8‐S10) shown that the frameworks stability to carry out the following researches. The profiles of adsorption and desorption for these compounds at room temperature (298 K) exhibit high uptake capability for polar molecules such as water (97 mg∙g1 for 1, 166 mg∙g1 for 2 and 186 mg∙g1 for 3), methanol (181 mg∙g1 for 1, 102 mg∙g1 for 2 and 159 mg∙g1 for 3) and ethanol (192 mg∙g1 for 1, 88 mg∙g1 for 2 and 161 mg∙g1 for 3) (Figure 2). Such elevated affinity for polar molecules may be attributed to the pbpy ligands which decorate pore wall with dicationic pyridinium units to optimize the adsorption capability of the molecules with larger polarity such as water (molecular dimension: 2.9×3.2×3.9 Å3), methanol (molecular dimension: 3.8×4.2×5.0 Å3) and ethanol (molecular dimension: 4.2×4.3×6.3 Å3). As show in Figure S8‐S10, the XRPD patterns after the water adsorption experiment demonstrate that the complexes 2 and 3 are stable. While the XRPD pattern of 1 shows obvious change, indicating the water molecules may influence the structural stability and lead to its inferior adsorption capability of water. The adsorption amount of methanol (181 mg∙g1) for 1 is comparable to the bipyridinium functional [Zn2(tpa)2(cpb)] framework with 36.3% void volume reported by Kitagawa and co‐workers.2 It is interesting to note that the enhanced accessibility to ethanol and methanol has been achieved in the presence of chloride, indicating the influence of halide anions on the guest adsorption performance of the compounds. The chloride ion has smaller radius but larger electronegativity than the bromide ion, thus may provide stronger
Figure 3. The 4,4’‐bipyridinium and bdc2 molecules constructed pore wall environments of the passageway as shown. The aromatic molecules can be captured by the π‐π interactions in the structure. There are two ingrowing halogen ions that point to the inner pore space and will influence the guest adsorption.
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hydrogen bonding sites. So, the compounds 1 and 3 are superior to 2 for the adsorption of methanol and ethanol. The larger molecules with some steric effects such as ethanol and methanol, can get more benefit from this additional interaction site and achieve an improvement during the guest adsorption process. Adsorption of Benzene, Toluene and Cyclohexane by the Bipyridinium Functionalized PCP Materials. In the crystal structure, the subtriangular 1D channel walls are full of the arene‐arene stacking fashions orderly piled by 4,4’‐bipyridinium and bdc2 moieties respectively. As shown in the Figure 3, the centroid distance of aromatic rings both in adjacent 4,4'‐ bipyridinium moieties (ligand B) and bdc2 molecules are 8.9 Å and 10.7 Å, respectively, indicating that benzene and toluene molecules can penetrate into the hole and be adsorbed on the wall though π‐π interaction. Additionally, there is another 1D channel with an arene‐arene stacked pyridyl rings and bdc2 molecules formed quadrate orifice (ca. 8.9×10.7 Å2) (Figure 4 and Supporting Information, Figure S11). It is a cage‐like pore space with unique cavity. From the side‐view perspective, we can find that the interior of the cage also exhibits arene‐arene stacking fashion that is favorable for storage of aromatic molecules. Therefore, benzene, toluene and cyclohexane adsorption behavior are measured based on these isomorphous complexes. It should be noted that these three complexes show a much larger uptake of benzene (200 mg∙g1 for 1, 137 mg∙g1 for 2 and 180 mg∙g1 for 3), toluene (197 mg∙g1 for 1, 158 mg∙g1 for 2 and 172 mg∙g1 for 3) and cyclohexane (111 mg∙g1 for 1, 121 mg∙g1 for 2 and 157 mg∙g1 for 3), which have comparable dimensions 3.3×6.6×7.3 Å3, 4.0×6.6×8.3 Å3 and 5.0×6.6×7.2 Å3, respectively (Figure 5).18,19 Recently, we have reported a bipyridinium‐
Figure 4. The frontal view (left) of the cage‐like pore space with a quadrate opening, and the side‐view (right) to look inside the perspective of internal structure.
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constructed framework with parallelogram‐like channels.5 Such porous material exhibited a benzene uptake of 52 mg∙g1. The compound 1 has the highest capacity for benzene and toluene storage, while 3 has the highest capacity for cyclohexane storage than any other metal‐bipyridinium frameworks known to date.5,20 It has been established in the literature that two kinds of porous MOFs constructed by aromatic carboxylic acid ligands11,21‐26 and azaaromatic ligands9,27‐31 exhibiting excellent adsorption properties (Supporting Information, Scheme S1‐S2). Compared with aromatic carboxylate based MOF materials, the benzene capacity of 1 (200 mg∙g1) is higher than that of the well‐known MOF‐199 (176 mg∙g1), MOF‐76 (145 mg∙g1) and the [Zn2(L)] skeleton (88 mg∙g1) built by 4,4'‐bipyridine‐2,6,2',6'‐tetracarboxylic acid, but lower than those for the Mn‐MOF‐74 (733 mg∙g1), MOF‐5 (802 mg∙g1) and NENU series materials (1687 mg∙g1 for NENU‐513) with the accessible void volume larger than 80% of the total volume.11,21‐26 It can be mainly attributed to the uniform micropore structure and higher pore volume of these aromatic carboxylate coordinated frameworks. In other class of azaaromatic ligands created MOFs, the most prominent representative is 2‐ethylimidazole and Zn(II) constructed nanoporous zeolitic metal azolate framework MAF‐6 which possesses rare RHO‐type structure and large and ordered pores to adsorb ca. 497 mg∙g1 of benzene.27,28 There are some characteristic ligands such as 1,4‐bis(4‐pyrazolyl)‐ benzene, benzene‐1,3,5‐triyltri‐isonicotinate and (R,R)‐(‐)‐N,N’‐bis(3‐tert‐butyl‐5‐(4‐ethynylpyridyl)‐ salicylidene)‐1,2‐diaminocyclohexane are introduced to build the MOFs Ni/Zn(bpb), [Cu2I2(BTTP4)] and [ZnL], with their benzene adsorption amount of 453/297, 255 and 118 mg∙g1, respectively.29‐31 Although the adsorption capability per unit mass of the current compounds is lower than some of the above typical MOFs, when calculated the amount according to the effective pore volume, the uptake of benzene, toluene and cyclohexane in 1 reaches an astonishing level of 840, 828 and 466 kg∙m3, respectively, indicating high utilization efficiency of the pore space. The adsorption amounts reach 548, 632 and 484 kg∙m3 for benzene, toluene and cyclohexane for 2, and 698, 667 and 609 kg∙m3 for benzene, toluene and cyclohexane for 3 at a high pressure of about P/P0 = 0.9, respectively. All these materials are better than the FMOF‐1 whose capacities of benzene, toluene and cyclohexane are reported as 290, 270 and 300 kg∙m3, respectively.9 Especially compound 1 accommodates 840 kg∙m3 of benzene, which is close to the best record of [Cu2I2(BTTP4)] (878 kg∙m3), and is higher than MOF‐5 (591 kg∙m3) and NENU‐511 (759 kg∙m3), while the adsorption amount of toluene (828 kg∙m3) per unit pore volume is the highest in record. The adsorption amount of cyclohexane for 3 (609 kg∙m3) is also attractive as compared with these typical MOF.
When estimating the adsorption limit by per unit cell, the data reveal that the best performance belong to PCP 1, which can uptake 5.8 benzene molecules per unit cell, 4.8 toluene molecules and 5.4 cyclohexane molecules per unit cell, respectively. Until now, the versatile materials with broad‐spectrum adsorption towards aromatic and nonaromatic organic pollutants are still less reported.9,11,21,29,31 The bipyridinium functional PCPs we developed belong to only a small number of MOFs that can adsorb aromatic benzene and aliphatic cyclohexane without mutually exclusive. The high utilization efficiency of the pore space and the facile synthesis of bipyridinium derivatives indicate their great potential in the field of porous materials. The research focal point in the future lies
Figure 5. Adsorption (filled symbols) and desorption isotherms (empty symbols) of benzene (a), toluene (b) and cyclohexane (c) at 298 K for three compounds.
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in improving accessible void volume of the bipyridinium functional PCPs materials in order to enhance the adsorption capacity. According to the experiment results, the PCP materials 1, 2 and 3 are all high‐performance adsorbents, especially compound 1 exhibits the most excellent adsorption property for benzene and toluene. As shown in the adsorption curves of 1, benzene, toluene and cyclohexane undergo rapid uptake at low pressure, reaching saturation at ca. P/P0 = 0.1, and the isotherms reveal a Type‐I sorption behavior as expected for material with micropores.26,32 The internal pore surface of 1 is comprised primarily of aromatic rings, so it is obvious that the aromatic vapors would be easily adsorbed via π‐π interactions. The rapid saturation and high uptake at low pressure indicate the presence of favorable host‐guest interactions through confinement effects for aromatic adsorbates.33,34 Desorption isotherms can also prove that the adsorbates are not easy to escape from the pores. Especially in the toluene desorption, the guest molecules are slowly released from the adsorbent along with the pressure decrease, when the system's pressure recover to normal atmospheric pressure, there are still ca. 120 mg∙g1 toluene staying in 1, 62 mg∙g1 staying in 2 and 101 mg∙g1 staying in 3, respectively. While the high absorption performance to nonaromatic cyclohexane is probably due to the cage‐like pore space, which possesses characteristic cavity space with the appropriate opening size. It is noted that the dihedral angles of 4,4’‐bipyridinium moiety both are nearly coplanar in 1 (2.9˚) and 2 (1.8˚), but the adsorption isotherms of 2 exhibit relatively low and slow uptake to reach saturation when adsorbing toluene (Figure 5 and Supporting Information, Table S1). This could be attributed to a great impact of different halides on the resultant porous properties. As shown in Figure 3, there are two coordinated chloride ions that point to the inner pore space and may form additional Cl∙∙∙π interactions for seizing aromatic molecules.35‐38 So, the PCP 1 exhibit higher capacity and faster adsorption saturation for aromatic adsorbates than 2.
CONCLUSIONS In summary, we have demonstrated a family of isomorphous PCPs exhibiting high broad‐spectrum adsorption capacity towards benzene, toluene and cyclohexane hydrocarbons of oil components. These PCPs can adsorb both hydrophilic and hydrophobic compounds, through a combination of properly sized 1D channel with charged pore surface and cage‐like pore space with arene‐ arene stacking fashion. The modulation of coordinated anions can significantly impact on the resultant porous properties, which provides not only a valuable insight into the mechanism for the host‐guest interaction, but also a guide to the development of a new class of adsorbent. Our results suggest that the current PCPs represent a promising class of porous materials that should find practical applications in the removal of organic pollutants, particularly in the field of oil spill cleanup and water pollution treatment.
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ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website at http://pubs.acs.org. XRPD pattern, FTIR spectrum, Energy‐ dispersive X‐ray spectroscopy, CO2 adsorption isotherms at 273 K, N2 adsorption isotherms at 77 K, additional crystal structure images and adsorption details (PDF). CCDC 1496985 (3).
AUTHOR INFORMATION Corresponding Author * E‐mail:
[email protected]. * E‐mail:
[email protected].
Notes The authors declare no competing financial interest.
ACKNOWLEDGMENT This work was supported by the NNSF of China (Grant Nos. 21573016/21403241/21271173/21571034), and the NSF of Fujian Province (No. 2014J01066).
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Flexible Bipyridinium Constructed Porous Frameworks with Superior Broad-Spectrum Adsorption toward Organic Pollutants Cheng Chen,†,§ Li‐Xuan Cai, § Bin Tan, § Ya‐Jun Zhang, § Xiao‐Dong Yang, § Shen Lin*† and Jie Zhang* ‡,§
A flexible bipyridinium ligand has been introduced into metal-organic frameworks to yield porous materials containing positively-charged 1D channel and arene-arene stacked cage-like pore space, which show broad-spectrum adsorptivity to organic pollutants with diverse structures and properties.
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