Porous MOF with Highly Efficient Selectivity and Chemical Conversion

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Porous MOF with Highly Efficient Selectivity and Chemical Conversion for CO2 Hai-Hua Wang,† Lei Hou,*,† Yong-Zhi Li, Chen-Yu Jiang, Yao-Yu Wang,*,† and Zhonghua Zhu‡ †

Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Materials Science, Northwest University, Xi’an 710069, P. R. China ‡ School of Chemical Engineering, The University of Queensland, Brisbane 4072, Australia S Supporting Information *

ABSTRACT: A new Co(II)-based MOF, {[Co2(tzpa)(OH)(H2O)2]· DMF}n (1) (H3tzpa = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid), was constructed by employing a tetrazolyl-carboxyl ligand H3tzpa. 1 possesses 1D tubular channels that are decorated by μ3−OH groups, uncoordinated carboxylate O atoms, and open metal centers generated by the removal of coordinated water molecules, leading to high CO2 adsorption capacity and significantly selective capture for CO2 over CH4 and CO in the temperature range of 298−333 K. Moreover, 1 shows the chemical stability in acidic and basic aqueous solutions. Grand canonical Monte Carlo simulations identified multiple CO2-philic sites in 1. In addition, the activated 1 as the heterogeneous Lewis and Brønsted acid bifunctional catalyst facilitates the chemical fixation of CO2 coupling with epoxides into cyclic carbonates under ambient conditions. KEYWORDS: metal−organic framework, crystal engineering, CO2 adsorption, chemical conversion, cycloaddition reaction, heterogeneous catalysis

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INTRODUCTION Carbon dioxide (CO2), mostly originating from the combustion of fuel as the main greenhouse gas, has caused great environmental concerns over the past few decades.1−4 Development of promising CO2 capture and sequestration (CCS) technologies is an imminent task to reduce CO2 from existing emission sources. Much effort has been dedicated to preparing versatile materials such as zeolites,5,6 porous organic polymers,7−11 amine-based solvents, and the recently developed metal−organic frameworks (MOFs)12−17 for CO2 capture. However, an innovative means of capture can turn to conversion of CO2 adsorbed in materials. The adsorbed CO2 molecules as feedstock could be further converted into other chemicals that would be more significant from both industrial and academic standpoints. Whereas the thermodynamic and kinetic stability of CO2 make the chemical fixation of CO2 difficult to achieve, CO2 is an inexpensive, nontoxic, and abundant renewable carbon resource.18 Inspiringly, porous MOFs due to endowed designable structures and facile pore functionalization can be designed to efficiently convert CO2 into valuable chemicals such as dimethyl carbonate,19 cyclic carbonate,20,21 and formic acid.22 Cyclic carbonates as important raw materials in industry are manufactured by the highly toxic phosgene; however, an alternative and green route is the insertion of CO2 into the C−O bond of epoxides during the coupling of epoxides with CO2 in the presence of catalysts, which does not generate any byproducts.23 © XXXX American Chemical Society

Many strategies such as creating open metal sites (OMSs) and incorporating functional groups in ligands were adopted to increase CO2 capture performance of MOFs.24−27 In this context, the combined advantages of adsorbent and heterogeneous catalyst ensure MOFs to be excellent candidates to meet the dual requirements of capture and conversion of CO2. In MOFs, OMSs behave not only as adsorption sites of CO2 but also as Lewis acid catalytic sites, while the accessible pores allow the retention of epoxides and their subsequent reaction with CO2.28−30 Although several known MOFs displayed good catalysis for the conversion of CO2 into cyclic carbonates, the high efficiency achieved at high temperatures (>80 °C) and high pressures (>2 MPa) causes a high energy cost.31−33 Under mild conditions, only sporadically existing MOFs, for example MMFC-2,34 MMPF-9, 28 and HKUST-1,35 revealed the relatively high catalytic efficiency for the coupling of CO2 with epoxides. Therefore, development of MOFs to realize the highly efficient catalysis for CO2 conversion under mild conditions is important and emergent. To reach the target of capture and conversion of CO2, MOFs should have several crucial features: good chemical and thermal stability, considerable adsorption capacity and selectivity for CO2, and high density of OMSs as Lewis acidic sites and/or other Brønsted acidic sites.36 In addition, the existence of Received: March 17, 2017 Accepted: May 11, 2017

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DOI: 10.1021/acsami.7b03835 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

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ACS Applied Materials & Interfaces

rpm). 1H NMR analysis was used to monitor the products and yields of products.

tubular channels in MOFs that promote the mass transfer of reactants more efficiently is especially desirable. Therefore, the design and construction of new MOFs with the abovementioned features is an appearing project for the capture and conversion of CO2. For this goal, 5-(4-(tetrazol-5yl)phenyl)isophthalic acid (H3tzpa) that contains the separated tetrazole and carboxylic acid coordination sites was employed to prepare MOFs. The incorporation of tetrazolyl group not only enriches the coordination fashion of H3tzpa but also benefits increasing the adsorption amounts of frameworks for CO2 because of its great attraction of rich-N atoms for CO2.37,38 Meanwhile, the relatively strong coordination bonds formed by azolates tend to produce a robust framework.39−41 Herein, a porous MOF, {[Co2(tzpa)(OH)(H2O)2]·DMF}n (1), was constructed, which shows particular chemical stability in acidic and basic aqueous solutions and possesses significant capture and selectivity for CO2 as well as highly efficient catalysis for the reaction of CO2 with propylene oxide into propylene carbonate under mild conditions due to the existence of a high density of OMSs and μ3−OH active sites.

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RESULTS AND DISCUSSION Structural Description. 1 crystallizes in monoclinic space group C2/c and reveals a 3D framework with tubular channels. The asymmetric unit contains three unique Co2+ ions, one tzpa, one μ3−OH ligand, and two coordinated water molecules (Figure 1a). All Co2+ ions show similar octahedrally six-

EXPERIMENTAL SECTION

Materials and General Methods. All solvents and starting materials for synthesis were purchased commercially. Infrared spectra were obtained in KBr discs on a Nicolet Avatar 360 FTIR spectrometer in the 400−4000 cm−1 region. Elemental analyses of C, H, and N were determined with a PerkinElmer 2400C elemental analyzer. Thermogravimetric analyses (TGA) were carried out in a nitrogen stream using a Netzsch TG209F3 equipment at a heating rate of 10 °C/min. Powder X-ray diffraction (PXRD) data were recorded on a Bruker D8 ADVANCE X-ray powder diffractometer (Cu Kα, 1.5418 Å). Sorption measurements were performed with an automatic volumetric sorption apparatus (Micrometrics ASAP 2020M). The sample was activated by heating the MeOH-exchanged compound at 220 °C under vacuum before sorption measurements. 1H NMR data were acquired on a Bruker Ascend 400 (400 MHz) spectrometer, and chemical shifts were reported in delta (δ) units in parts per million (ppm) downfield from tetramethylsilane. Synthesis of {[Co2(tzpa)(OH)(H2O)2]·DMF}n (1). A mixture of Co(NO3)2·6H2O (0.0291 g, 0.1 mmol) and H3tzpa (0.0155 g, 0.05 mmol) in H2O (3 mL) and DMF (4 mL) solvents was sealed in a vessel (25 mL). The vessel was heated at 105 °C for 72 h and then cooled to room temperature at a rate of 5 °C/h, affording the red block crystals of 1 with a yield of ca. 23.1 mg (83.8%, based on H3tzpa). Anal. Calcd for C18H17N5O8Co2: C, 39.22; H, 3.47 N, 12.70%. Found: C, 39.36; H, 3.60; N, 12.61%. IR (KBr, cm−1): 3404(s), 3044(w), 2937(w), 2872(w), 1656(vs), 1620(m), 1560(m), 1462(m), 1370(s), 1093(m), 843(w), 771(m), 718(m), 665(w), 541(w). X-ray Crystallographic Measurements. A Bruker Smart Apex II CCD detector was employed to obtain the crystal data of complex 1 at 296(2) K using ω rotation scans with widths of 0.3° and Mo Kα radiation (λ = 0.71073 Å). The structure was solved by direct methods and refined by full-matrix least-squares refinement based on F2 with the SHELXTL program.42 All non-hydrogen atoms were refined anisotropically with the hydrogen atoms added at their geometrically ideal positions and refined isotropically. It failed to refine the solvent molecules with the right models; therefore, the SQUEEZE routine of Platon program43 was applied. The single-crystal analysis together with elemental microanalyses and TGA data gave the final formula of the complex. Relevant crystallographic results and bond lengths/angles are listed in Tables S1 and S2, respectively. Catalytic Experiment. The catalytic reactions were conducted at the ambient temperature and 1 atm pressure under solvent free environment in a 5 mL Schlenk tube using epoxides (20 mmol) with CO 2 catalyzed by activated 1 and a cocatalyst of tetra-ntertbutylammonium bromide (TBAB) under stirring for 48 h (800

Figure 1. (a) Coordination environment of Co(II) ions in 1. Symmetry codes: (1) −x, −y, 1−z; (2) −0.5+x, 0.5−y, −0.5+z; (3) −0.5+x, −0.5−y, −0.5+z; (4) x, −y, −0.5+z; (5) −x, y, 0.5−z. (b) Metal−azolyl−hydroxy ribbon-like SBU.

coordinated environments, in which Co1 is surrounded by three carboxylate O atoms, two tetrazolate N atoms, and one hydroxy O atom, while both Co2 and Co3 are coordinated by two tetrazolate N atoms, two hydroxy O atoms, and two water molecules located at the two axial apexes of an octahedron. Three Co atoms are connected by one μ3−OH group and three tetrazolates to generate a triangular trinuclear cluster [Co3(μ3− OH)(N4C)3] with the Co···Co separations of 3.39−3.52 Å. One tzpa links six Co atoms through four N atoms of one tetrazolate and three O atoms of two carboxylates. The Co3(μ3−OH) triangles are confused by an edge- and/or corner-sharing fashion to form an unusual infinite metal− azolyl−hydroxy ribbon-like secondary building unit (SBU) along the c-axis (Figure 1b). This ribbon with unique zigzag Δchain arrangement for Co atoms is observed in extremely rare metal−azole systems,44−47 greatly distinguishing from the metal−carboxylate chain SBUs frequently reported in MOFs. The SBU in 1 is extended by tzpa to produce a 3D open framework. The framework contains tubular channels (open sizes ca. 10.4 × 7.5 Å2) along the c-axis with the solvent accessible voids of 31.2% (Figure 2). The channel is encircled by uncoordinated carboxylate O atoms of tzpa and ribbon SBUs. Strikingly, when the axial water ligands of Co (Co2 and Co3 atoms) octahedral coordination spheres are removed, the multiple OMSs behaving as Lewis acid sites are created, which together with μ3−OH groups (Brønsted acid sites) are alternatively distributed on the top and down sides of ribbon, forming a high density of Lewis and Brønsted acid catalytic sites of platform. Therefore, the channels in 1 would be highly active for adsorption and catalysis. PXRD and TGA. The phase purity of bulk crystalline sample of 1 was confirmed by coincident PXRD patterns between the B


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similar type-I microporous isotherms for five gases and has the highest uptake for CO2 (154 cm3 (STP) g−1 at 100 kPa; Figure 3a), from which a BET surface area of 455 m2 g−1 (Langmuir surface area 532 m2 g−1) is obtained. According to Horvath− Kawazoe model, the pore size distribution curve based on N2 adsorption isotherm at 77 K shows the main size range of 4.1− 7.1 Å (Figure S5), agreeing with that of the crystal structure. At 298 K and 100 kPa, 1a shows low CH4 uptake (15.6 cm3 (STP) g−1, 1.2 wt %) and very little CO uptake (7.9 cm3 (STP) g−1, 1.0 wt %) but a high CO2 loading of 63.8 cm3 (STP) g−1 (12.5 wt %) (Figures 3b−d). This CO2 amount is moderately high compared to the highest value of 9.1% in ZIF-78 in zinc imidazolate frameworks48 and greatly outperforms the values reported in some Zn4O-based nanoporous MOFs (3.4−7.3 wt %).49−52 The significant CO2 uptake in 1a is attributed to the existence of accessible OMSs, μ3−OH groups, and uncoordinated carboxylate O sites, which can generate strong affinity toward CO2. In the interest of assessing the separation performance of 1a for CO2, the CO2/CH4 selectivity for CO2−CH4 mixtures at a general feed composition of landfill gas (CO2/CH4 = 50:50) and natural gas (CO2/CH4 = 10:90 and 5:95), were analyzed using ideal adsorbed solution theory (IAST) model (Figures S6a and b).53 As shown in Figures 4a−c, 1a displays high CO2/ CH4 selectivities of 31.8, 32.2, and 33.1 at 100 kPa and 298 K for the mixtures with 50, 10, and 5% CO2 components, respectively. These values lie in the upper region of the reported MOFs (Table S3). The CO2 adsorption capacity of 1a was also evaluated at higher temperatures of 313 and 333 K, which fall within the practical temperature ranges of flue gas in the postcombustion process. 1a at 100 kPa adsorbs 55.8 and 30.6 cm3 (STP) g−1 CO2 at 313 and 333 K, respectively, which are comparable to those in SIFSIX-3-Zn54 and bio-MOF-1255 but surpass the values reported in major MOFs under similar

Figure 2. 3D framework of 1 with 1D tubular channels along the caxis.

calculated and measured (Figure S1). When 1 was immersed into the distilled water up to 5 days and acidic (pH = 2 and 4) and basic (pH = 12) aqueous solutions for 24 h, respectively, PXRD confirmed the remarkable chemical stability of 1 (Figure S1). TGA of 1 reveals the release of DMF guests and coordinated water molecules with a weight loss of 17.4% from 30 to 280 °C (calc. 14.1%) (Figure S2). The guest-free framework [Co2(tzpa)(μ3−OH)] (1a) was obtained by heating the MeOH-exchanged sample of 1 at 220 °C under vacuum. The removal of water ligands and DMF solvent molecules in 1a was evidenced by Fourier transform infrared (FTIR) spectroscopy with the absence of both characteristic CO vibration of DMF and weight loss before 300 °C (Figure S3). 1a shows a thermal plateau before 300 °C. Although the PXRD pattern of 1a is slightly amorphous, the fully restored diffraction peaks of 1a immersed in DMF corroborate the framework integrity of 1a (Figure S4). Gas Sorption. The removal of water ligands in Co2+ ions produces the highly polar channels decorated by OMSs, μ3− OH groups, and uncoordinated carboxylate O atoms in 1a, which inspires us to estimate the porosity by gas adsorptions of N2 and H2 at 77 K, CO2, CH4, and CO at 195 K. 1a exhibits

Figure 3. (a) Sorption isotherms of N2 and H2 at 77 K and CO2, CH4, and CO at 195 K for 1a. (b) Sorption isotherms of CO2 and CH4 for 1a at ambient temperatures. (c) Sorption isotherms of CO at ambient temperatures. (d) Comparison of gas sorption at 100 kPa. C


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Figure 4. (a−c) CO2/CH4 selectivity for CO2/CH4 binary mixtures with 50, 10, and 5% CO2 concentrations, respectively. (d) CO2/CO selectivity for CO2/CO mixtures with different CO2 concentrations at 100 kPa.

adsorption heat of 28.3 and 18.5 kJ mol−1, respectively (Figures S9 and S10). Notably, when 1a is exposed in air with some degree of humidity for 2 weeks, its 5 cycles of CO2 adsorption isotherms at 298 K reveal almost equal capacities after being activated again (Figure 5), which indicates stability of the framework.

conditions (Table S4) such as Cu3(BTC)2 (34.0 cm3 (STP) g−1, 313 K)56 and Mo3(BTC)2(DMF)0.5 (24.2 cm3 (STP) g−1, 333 K).57 The CO2/CH4 selectivities at 100 kPa are 16.9, 22.3, and 24.2 at 313 K and 11.8, 15.0, and 17.1 at 333 K for CO2/ CH4 mixtures with 50, 10, and 5% CO2 components, respectively (Figures 4a−c). The significant CO 2 /CH 4 selectivity makes 1a a candidate applied for CO2 capture from landfill gas and natural gas in a wide temperature range. In addition, the IAST CO2/CO selectivity of 1a for CO2/CO mixtures was also assessed (Figure S6c). In the region of CO2 components changed from 5 to 95%, 1a displays very high CO2/CO selectivities with the values in the range of 67.5−82.7, 59.6−71.9, and 17.9−25.7 at 100 kPa and 298, 313, and 333 K, respectively (Figures 4d and S7); Therefore, 1a as a potential absorbent could also be applied in the capture of CO2 from various gases wherein CO exists. The significant selectivity of 1a for CO2 over CH4 and CO is attributed to the existence of multiple CO2-philic sites in channels such as OMSs and μ3−OH groups, which form specific interactions with CO2 due to the larger quadrupole moment and higher polarizability value of CO2 relative to that of CH4 and CO. The uncoordinated carboxylate O atoms in channels can also contact with CO2 by dipole−quadrupole interactions. The isosteric heat (Qst) was calculated by the virial equation58 from the CO2 adsorption isotherms at 273 and 298 K. The Qst of 1a is 38.5 kJ mol−1 for CO2 at zero loading and declines to 27.9 kJ mol−1 at 63.9 cm3 (STP) g−1 (Figure S8). This initial Qst for CO2 is comparable to those of MOFs decorated by typical active sites such as Lewis basic sites (LBSs), OMSs, and other representative MOFs (Table S5),59,60 suggesting strong framework−CO2 interactions. In contrast, 1a shows weak interactions for CH4 and CO with the low initial

Figure 5. CO2 uptake of pristine 1a and 5 cycles of CO2 uptake of 1a at 298 K after 2 weeks of exposure to air.

Grand Canonical Monte Carlo (GCMC) Simulations. The interactions of 1a with CO2 at 298 K were elucidated by GCMC simulations (Supporting Information). Four favorable binding sites were observed around the ribbon in the channel at 100 kPa (Figure 6). CO2−I is close to the Co3(μ3−OH) triangles, in which one electronegative OCO2 atom forms moderate O−H···O hydrogen bond (O···H 3.049 Å) with one μ3−OH group and weak contacts with two open Co sites as well; the corresponding O···Co distances of 3.77 and 3.75 Å are slightly longer than the sum of van der Waals radii of O (1.52 D


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increase in molecular sizes of epoxide substrates leads to greatly decreased yields of cyclic carbonates from 53.6% for butylene carbonate (Table 1, entry 6) to 48.3% for 3-butoxy-1,2propylene carbonate (Table 1, entry 7) formed by butylene oxide and butyl glycidyl ether, respectively. This phenomenon should be ascribed to the hindrance effect of the pores in 1a, which decreases the diffusion of the large-sized epoxide molecules, displaying size-selective catalysis to a degree. By comparing the sizes of pores in 1a and substrates (Figure S11), it infers that the pores allow the entrance of substrate molecules in the catalysis process, especially for propylene epoxide with small sizes. This fact certifies that the reactions happened inside pores. In addition, the catalytic yields for propylene carbonate in 1a are almost identical (93.8, 93.5, 93.1, and 92.8%) in the four recycling experiments. Binary catalytic systems for the reactions of epoxides with CO2 coupling usually combine a Lewis acid and a nucleophile (such as a halide anion), making the ring opening procedure energetically less demanding and the subsequent CO2 insertion easier. The mechanism for the reaction of epoxides with CO2 into cyclic carbonates by 1a was attributed to the existence of the OMSs of Co2+ ions and μ3−OH groups, which serve as potential Lewis and Brønsted acidic bifunctional catalytic sites (Scheme 2).18 First, the coupling reaction in 1a was triggered by the activation of the epoxy ring caused by two catalytic sites contacting the O atom of the epoxide. Second, the Br− nucleophile from TBAB attacked the less hindered C atom of the epoxide. Finally, the alkylcarbonate anion was formed by the interactions of CO2 with the oxygen anion of the opened epoxy ring, which was further converted into the corresponding cyclic carbonates through the ring-closing step. In addition, GCMC simulation confirmed two different interaction fashions between the ribbon and propylene epoxide in the channels of 1a (Figure 7). One open Co2+ ion forms strong Co···O interactions (Co···O = 2.171−2.204 Å) with one or two propylene epoxide molecules located at two sides of the ribbon. Meanwhile, the propylene epoxide also form O−H···O hydrogen bonds (H···O = 2.558−2.566 Å) with μ3−OH groups in the ribbon. The synergistic effect of a high density of Lewis and Brønsted acidic sites in 1a together with significant uptake of CO2 was believed to be the main reason for the high activity of catalysts for the coupling reactions between epoxides and CO2. The related MOF catalyst containing Lewis and Brønsted acidic bifunctional catalytic sites was rarely reported in past.36,59

Figure 6. Four simulated favorable CO2 adsorption sites in 1a at 298 K.

Å) and Co (2.03 Å) atoms. The electropositive CCO2 atom of CO2−I interacts with the uncoordinated carboxylate O atom in channels. The C···O separation of 3.376 Å is approximate to the sum of van der Waals radii of C (1.70 Å) and O (1.52 Å), indicating moderate interactions. CO2-II and CO2-III are both directed toward the exposed Co atoms and form strong Co··· OCO2 contacts with the Co···O distances of 2.429 and 2.741 Å. One O atom of CO2-IV is also involved in the Co···O interaction (Co···O = 2.333 Å) with the Co atom and O−H··· O (O···H = 2.348 Å) hydrogen bond with one μ3−OH group in Co3(μ3−OH) triangles. The simulation clearly reveals that the OMSs and μ3−OH groups behave as important binding sites for CO2 molecules; in particular, the CO2 molecules can attack the open sites of Co centers from up and down. Catalytic Cycloaddition of CO2 and Epoxides. MOFs as heterogeneous catalysts for chemical conversion of CO2 into cyclic carbonates have been demonstrated but under the conditions of high pressure (>2 MPa) and high temperature (>80 °C).28−33 In 1a, the exposed sites of Co2+ ions and μ3− OH groups in ribbon can serve as potential Lewis and Brønsted acidic sites, respectively. Together with significant uptake and selectivity for CO2, the catalytic ability of 1a for the cycloaddition of CO2 and epoxides to form cyclic carbonates was explored at a mild condition of 298 K and 100 kPa (Scheme 1). The results are summarized in Table 1. The yields Scheme 1. Synthesis of Cyclic Carbonates by the Coupling Reaction of Epoxides with CO2

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CONCLUSION In summary, a new Co(II)-based MOF was successfully constructed by a bifunctional tetrazolyl-carboxyl ligand, which shows uncommon chemical stability toward acid and basic aqueous solutions. The activated framework 1a contains 1D tubular channels decorated by high density of active sites: OMSs, μ3−OH groups, and uncoordinated carboxylate O atoms. Consequently, 1a reveals high CO2 adsorption capacity and significant CO2/CH4 and CO2/CO selectivities in 298− 333 K. Meanwhile, the OMSs and μ3−OH groups in 1a behave as Lewis and Brønsted acidic bifunctional catalysis sites, respectively, and efficiently catalyze the coupling reactions between propylene epoxide and CO2 under ambient conditions to afford propylene carbonate with a high yield. In addition, GCMC confirmed the multiple CO2-philic sites and also identified the interacting details between the bifunctional catalysis sites and propylene epoxide substrates.

for propylene carbonate in different reactions proved that the combination of 1a and TBAB would be a good binary catalyst for the formation of propylene carbonate. A high yield of 93.8% propylene carbonate was achieved at a molar ratio of 100/10/1 for epoxide/TBAB/1a over 48 h (Table 1, entry 5). This yield is comparable to those reported in MMPF-9 under similar conditions and Cu 3 (BTC) 2 at high temperature and pressure.28,33 Furthermore, we also examined the performance of 1a in chemical fixation of CO2 with different functional group substituted epoxides under ambient conditions. The E


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ACS Applied Materials & Interfaces Table 1. Cycloaddition of CO2 and Epoxide under Various Reaction Conditionsa

a

The same reaction conditions: epoxide, 20 mmol; CO2 pressure,100 kPa; reaction temperature, 298 K; reaction time, 48 h.

Yao-Yu Wang: 0000-0002-0800-7093 Zhonghua Zhu: 0000-0003-2144-8093

Scheme 2. Reaction Mechanism for the Catalytic Conversion of CO2 with Epoxides into Cyclic Carbonates

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by NSFC (Grants 21471124, 21371142, and 21531007), NSF of Shannxi province (2013KJXX-26 and 15JS113), and the Australian Research Council Future Fellowship FT12010072.

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Figure 7. (a and b) Two different interaction modes of ethylene oxide molecules with the ribbon in 1a.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b03835. TGA, PXRD, 1H NMR, sorption patterns, bond length/ angle tables, and additional figures (PDF) Crystallographic information for 1, CCDC 1529068 (CIF)

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*E-mail: [email protected]. *E-mail: [email protected]. ORCID

Lei Hou: 0000-0002-2874-9326 F


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Porous MOF with Highly Efficient Selectivity and Chemical Conversion

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