Tuning the Structure of Fe-Tetracarboxylate Frameworks Through Linker-Symmetry Reduction

Abstract

Open AccessCCS ChemistryCOMMUNICATION1 Feb 2021Tuning the Structure of Fe-Tetracarboxylate Frameworks Through Linker-Symmetry Reduction Jiandong Pang†, Christina T. Lollar†, Sai Che, Jun-Sheng Qin, Jialuo Li, Peiyu Cai, Mingyan Wu, Daqiang Yuan, Maochun Hong and Hong-Cai Zhou Jiandong Pang† Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 , Christina T. Lollar† Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 , Sai Che Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 , Jun-Sheng Qin State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, International Center of Future Science, Jilin University, Changchun 130012 , Jialuo Li Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 , Peiyu Cai Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 , Mingyan Wu *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 University of Chinese Academy of Sciences, Beijing 100049 , Daqiang Yuan State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 University of Chinese Academy of Sciences, Beijing 100049 , Maochun Hong State Key Laboratory of Structure Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 University of Chinese Academy of Sciences, Beijing 100049 and Hong-Cai Zhou *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] Department of Chemistry, Texas A&M University, College Station, TX 77843-3255 https://doi.org/10.31635/ccschem.020.202000348 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail The design and synthesis of stable metal–organic frameworks (MOFs) have been a core obstacle in the widespread application of these functional crystalline porous materials, because of the stability limitations of MOFs under harsh operating conditions. Herein, a highly stable microporous MOF based on the Fe3O cluster (PCN-678) has been synthesized using a tetracarboxylate ligand. Utilizing symmetry reduced tetratopic carboxylate ligand, a mesoporous MOF (PCN-668) could be obtained in which nanoscale cage-like building units and one-dimensional (1D) channels coexist. The neighboring cages were mutual diastereomers in PCN-668 due to the further reduction of the Cs symmetry of the free ligand to C1 symmetry after self-assembly. Furthermore, the acid stability of this mesoporous MOF was improved via postsynthetic metal exchange to chromium (PCN-668-Cr). The PCN-668-Cr exhibited very high stability in both acidic and basic aqueous solutions (pH = 1–11). Additionally, the mesoporous MOF showed a high total gravimetric methane uptake (∼500 cm3 g−1 at 100 bar), while the microporous MOF showed a high volumetric methane storage capacity of 147 cm3 cm−3 at room temperature. Download figure Download PowerPoint Introduction Constructed of metal ions/metal clusters and organic ligands, metal–organic frameworks (MOFs), or porous coordination networks (PCNs), are modular, crystalline, porous materials displaying high specific surface areas, large pore volumes, and precisely adjustable pore environments.1–5 In the past two decades, more than 20,000 MOFs have been designed and synthesized utilizing numerous organic ligands and metal ions/metal cluster variations, with promising potential in gas adsorption, energy storage, smart sensors, and heterogeneous catalysis.6–18 Labile coordination bonds between low-valence metals and carboxylate-containing organic ligands elicit chemical instability in many MOFs to water, acid, or base, dramatically limiting their further applicability and commercialization.19 According to the hard/soft acid/base (HSAB) principle, fabrication of ultrastable MOFs could be targeted through the use of high-valent, hard Lewis acids, known to form more resilient bonds with carboxylate ligands. For example, the UiO (UiO represents University of Oslo) series MOFs based on Zr4+ clusters and the MIL (MIL represents Material Institute Lavoisier) series MOFs based on M3+ (M = Cr, Al, Fe, etc.) clusters exhibit considerably improved stability, compared with MOFs made from divalent metals such as Zn2+ or Cu2+ ions/clusters.20–22 Our group has long focused on the design and synthesis of ultrastable MOFs. A series of highly stable MOFs based on Zr6 clusters and Fe3 clusters have been obtained under the guidance of HSAB principles.23–26 It is particularly worth mentioning that Zr6 cluster-based PCN-222 and Fe3 cluster-based PCN-600 are rare examples of ultrastable MOFs with mesoporosity.26,27 The metal clusters in both of the two MOFs mentioned above are linked by the same square planar, tetratopic, carboxylate ligand, tetrakis(4-carboxyphenyl)porphyrin (H4TCPP), which adopted a high D4h symmetry in the two frameworks. We have reported earlier a systematic study of controlling the structure of Zr-tetracarboxylate frameworks through steric tuning of tetratopic carboxylate ligands.24 Based on our previous work, these series of ligands were combined with trinuclear iron clusters to construct highly stable MOFs with intriguing structures. Interestingly, these ligands adopted lower symmetries in the Fe frameworks than in the Zr frameworks. Results and Discussion Initially, we selected unsubstituted H4TPCB and 2,2'-OH-H4TPCB as organic linkers in the synthesis of Fe frameworks, but no crystalline product could be obtained. When substituents were introduced into the 4,4′-positions, a two-dimensional (2D) MOF, PCN-648 (Figure 1f and Supporting Information Figure S1), based on 4,4′-NH2-TPCB (Figure 1h) and the Fe3O cluster (Figure 1g) and a three-dimensional (3D) microporous MOF, PCN-678 (Figure 1a), based on 4,4′-OMe-TPCB (Figure 1c) and Fe3O clusters (Figure 1d) were formed. The 4,4′-NH2-TPCB ligand adopts a D2 symmetry in PCN-648 with a dihedral angle of 35.13° between the two inner phenyl rings, while the 4,4′-OMe-TPCB ligand adopts a C2 symmetry in PCN-678 with the two inner phenyl rings coplanar. Interestingly, while the metal cluster in PCN-678 was six connected as expected, the cluster in PCN-648 was four connected with two sites occupied by terminally coordinated formate and acetate molecules (Figure 1g). From a topological point of view, the simplification of the 4,4′-OMe-TPCB4− ligands as four-connected nodes and the Fe3 clusters as six-connected nodes enabled PCN-678 to adopt a new (4,6)-c net with a topological point symbol of {42.63.8}3{43.69.83}2 (Figure 1a). In Zr-tetracarboxylate framework systems, increasing the size of the substituents in the 4,4′-position prompted the formation of mesoporous, csq-topology MOFs (PCN-608).24 Therefore, the 4,4′-OCy-TPCB ligand (Figure 1j), with its large substituents, was also studied in the Fe-tetracarboxylate framework system. However, direct synthetic methods using this ligand yielded only a microporous MOF, termed PCN-658 (Figure 1k and Supporting Information Figure S2). The ligand in PCN-658 adopted a D2 symmetry with a dihedral angle of 48.89° between the two inner phenyl rings similar to that of 4,4′-NH2-TPCB in PCN-648. Strangely, no trinuclear cluster was observed in PCN-648. Instead, an iron chain was formed, bridged by two carboxylate groups from the linker and one formate (Figure 1i). In our previous work, we developed a strategy to construct iron MOFs based on trinuclear iron clusters using presynthesized clusters.28 Therefore, synthesis with 4,4′-OCy-TPCB ligands was attempted using the presynthesized trinuclear iron clusters instead of Fe(NO3)3. Again, attempts to obtain PCN-648 with trinuclear iron clusters rather than iron chains failed. Figure 1 | The crystal structures of PCN-678, PCN-668, PCN-648, and PCN-658. (a) Perspective view of PCN-678 along the c-axis and the (4,6)-c topology of the microporous framework. (b) Perspective view of PCN-668 along the c-axis and the (4,6)-c topology of the mesoporous framework. (c) The four connected, C2 symmetry 4,4′-OMe-TPCB4− ligand. (d) The six-connected trigonal-prismatic [Fe3O(RCOO)6] cluster. (e) The four connected, Cs symmetry CBTB4− ligand. (f) The 2D structure of PCN-648. (g) The four-connected trigonal-prismatic [Fe3O(RCOO)4] cluster. (h) The four connected, D2 symmetry 4,4′-NH2-TPCB4− ligand. (i) The 1D metal chain in PCN-658. (j) The four connected, D2 symmetry 4,4′-OCp-TPCB4− ligand. (k) The 3D framework of PCN-658. Color scheme: black, C; red, O; blue, N; light blue, Fe; green, terminally coordinated formates and acetates. For clarity, H atoms are not shown. Download figure Download PowerPoint Matzger and co-workers29–31 confirmed earlier that diverse MOF structures could be obtained using reduced symmetry ligands. We have also fabricated a series of multicomponent Zr-MOFs successfully using a reduced symmetry ligand H4CBTB (4,4',4'',4'''-(9H-carbazole-1,3,6,8-tetrayl)tetrabenzoic acid) (PCN-609 series).32–34 Bearing this in mind, the trapezoidal, tetratopic carboxylate ligand, H4CBTB (Figure 1e), was selected to construct new iron MOFs with intriguing structures. Solvothermal reactions of H4CBTB, Fe(NO3)3·9H2O, and acetic acid in DMF afforded the mesoporous framework complex [Fe6(μ3-OH)2(CBTB)3(H2O)6]·(solvent)x, termed PCN-668. Single-crystal X-ray diffraction experiments at 100 K revealed that PCN-668 was constructed from fully deprotonated CBTB4− ligands and trinuclear [Fe3O(COOR)6] clusters, crystallizing in the hexagonal space group P63/mcm. Each CBTB4− ligand coordinates to four Fe3 clusters, and each Fe3 cluster linked to six CBTB4− ligands (Figure 1b). Combination of six CBTB4− ligands and eight Fe3 clusters form a cubic cage-like secondary building unit (SBU) with dimensions of approximately 18 Å (Figure 2a). The cubic nanocage SBU is slightly distorted because of the low symmetry of the CBTB4− ligands, and distortion of the clusters. Each cage was linked to two neighboring cages through the sharing of one Fe3 cluster vertex on the two poles and four neighboring cages through the sharing of two Fe3 cluster vertices (or one edge) in the equatorial plane ( Supporting Information Figure S3). On the whole, the cubic cages were connected to form a 3D, noninterpenetrated network ( Supporting Information Figure S4). Also, the one by one connection of the nanocages gave rise to a very large round channel with the cubic nanocages arranged neatly on the walls of the channel (Figure 1b). The mesoporous channels opened along the c-axis with dimensions of approximately 22 Å. For a more precise description of the framework, the CBTB4− ligands might be simplified as four-connected nodes and the Fe3 clusters as six-connected nodes. In this way, PCN-668 adopted a new (4,6)-c net with a topological point symbol of {410.64.8}3{44.62}6{46.89} ( Supporting Information Figure S5). Figure 2 | (a) The diastereomeric cage-like SBUs observed in PCN-668. (b) The ideal Cs symmetry and the C1 symmetrical CBTB4− ligands in PCN-668. Color scheme: black, C; red, O; light blue, Fe. For clarity, H atoms are not shown. SBU, secondary building unit. Download figure Download PowerPoint Interestingly, any two neighboring nanocages in PCN-668 occurring through any symmetrical operation was not coincidental; that is, they were stereoisomeric cages (Figure 2a). To the best of our knowledge, this is the first fabricated mesoporous MOF based on diastereomeric polyhedral nanocages. The CBTB4− ligand favors Cs symmetry with a symmetrical mirror, as was observed in the Zr-based framework PCN-609. However, the self-assembly of CBTB4− ligands with Fe3O clusters forced the ligand to asymmetry, producing chiral cage-like units (Figure 2b). Overall, the m symmetrical plane in PCN-668 made it a mesomeric framework. The hexagonal single crystals of PCN-668 ( Supporting Information Figure S6) were obtained with a significant amount of rectangular polycrystal impurity after a week-long solvothermal reaction with 3 mL acetic acid at 150 °C. Considering that the acidity of the reaction system played an essential role in the synthesis of zirconium-based MOFs, the crystal growth conditions were subjected to minor revisions with a carefully regulated dosage of the acetic acid moderator to obtain a purer phase PCN-668.28,35–37 When 1 mL of acetic acid was added to adjust the pH of the reaction mixture, pure microcrystalline PCN-668-Fe was obtained after 3 days at 150 °C, as confirmed by powder X-ray diffraction (PXRD) experiments (Figure 3c). Figure 3 | Stability tests of the microporous and mesoporous MOFs. PXRD patterns of (a) PCN-678, (c) PCN-668, and (e) PCN-668-Cr. N2 adsorption isotherms for (b) PCN-678, (e) PCN-668, and (f) PCN-668-Cr. MOFs, metal–organic frameworks; PXRD, powder X-ray diffraction. Download figure Download PowerPoint The frameworks of PCN-648 and PCN-658 collapsed after removal of the mother liquor, indicative of low stability. Therefore, no porosity-related data can be obtained. The solvent-accessible volumes in fully evacuated PCN-678 and PCN-668 were 56.4% and 81.2%, respectively, calculated by PLATON with a probe of 1.8 Å. To check the permanent porosity of PCN-678 and PCN-668, nitrogen adsorption isotherms were measured at 77 K and 1 atm. As shown in Figures 3b and 3d, the N2 sorption of PCN-678 exhibited a typical type I isotherm with a saturated adsorption amount of 416 cm3 g−1, signifying the microporous nature of PCN-678. In contrast, the N2 sorption of PCN-668 displayed a typical IV isotherm with a saturated adsorption amount of 1311 cm3 g−1, signifying the mesoporous nature of PCN-668. The Brunauer–Emmett–Teller (BET) apparent surface areas of PCN-678 and PCN-668 calculated from the N2 adsorption data were 1720 ± 5 and 2772 ± 25 m2 g−1, respectively. The pore size in activated PCN-678 and PCN-668 was also analyzed by the nonlocal density functional theory (NLDFT) model from the N2 adsorption data with a narrow distribution of micropores ∼1.2 nm for PCN-678 and narrow distribution of micropores ∼1.5 nm and mesopores around 3.0 nm for PCN-668 ( Supporting Information Figure S7). We investigated the chemical stability of these microporous and mesoporous MOFs after washing with DMF and deionized water, followed by as-synthesized crystalline samples of PCN-678 and PCN-668 immersion in aqueous solutions with pH = 1, 7, and 11 for 24 h. The PXRD patterns showed that the frameworks remained intact after acidic or basic solution treatment, implying that neither framework collapse nor phase transition occurred during the stability testing (Figures 3a and 3c). The N2 adsorption of the microporous MOFs after treatment showed typical type I isotherms with a slight change of the adsorption amount (Figure 3b). However, as shown in Figure 3d, the nitrogen adsorption isotherm at 77 K of the acidic solution-treated mesoporous MOF sample showed a rapid increase in the high-pressure region (0.8–1 atm). This phenomenon was attributed to the partial collapse of the framework and the formation of macropores, indicating instability of the mesoporous MOF under acidic conditions. According to literature reports, trinuclear chromium-based MOFs could be obtained via postsynthetic routes, which might be more stable than the original MOF.38,39 Therefore, solvent-assisted metal metathesis was applied to PCN-668 to yield the Cr(III) analog PCN-668-Cr (Figures 4a and 4b). Briefly, PCN-668 was dispersed in a solution of CrCl3·6H2O in acetone and heated for ∼4 h at 80 °C. This procedure was repeated three times, and PCN-668-Cr was obtained. As shown in Figures 4e and 4f, the sample color changed from orange to green after the metal exchange, and scanning electron microscopy (SEM) images show smoothing of the MOF crystals (Figures 4c and 4d). Energy-dispersive spectrometry (EDS) mapping, as well as inductively coupled plasma (ICP) analysis, were recorded for PCN-668 before and after metal exchange to confirm the almost full exchange of Fe for Cr ( Supporting Information Figure S8). The chemical stability of the new Cr(III)-based MOF was also examined. As expected, PCN-668-Cr boasted higher acid stability as confirmed from N2 adsorption isotherms after acidic aqueous solution treatment (Figure 3e and 3f). Figure 4 | Comparison of PCN-668-Fe and PCN-668-Cr. Crystal structures of (a) PCN-668-Fe and (b) PCN-668-Cr. SEM images of (c) PCN-668-Fe and (d) PCN-668-Cr. Images of (e) activated PCN-668-Fe and (f) activated PCN-668-Cr. SEM, scanning electron microscopy. Download figure Download PowerPoint Considering the high porosity and stability of these microporous and mesoporous MOFs, high-pressure methane uptake properties were measured at room temperature. As shown in Figures 5a–5f, the microporous PCN-678 showed a total gravimetric methane uptake of 287 cm3 g−1 at 90 bar, while the mesoporous PCN-668 and PCN-668-Cr exhibited much higher total gravimetric methane uptakes of 467 and 462 cm3 g−1, respectively, at 90 bar. The relatively high gravimetric methane working capacity of the mesoporous MOFs (421 cm3 g−1 for PCN-668 and 408 cm3 g−1 for PCN-668-Cr from 90 to 5 bar) was attributed to the high pore volume of the frameworks. The gravimetric methane working capacity of PCN-668 at 298 K and 65 bar was 333 cm3 g−1, which was higher than that of NOTT-102, MOF-5, PCN-80, and UTSA-76 (NOTT represents University of Nottingham, UTSA represents University of Texas at San Antonio, Supporting Information Table S1).40–43 However, considering the crystal density, the volumetric methane total uptake of PCN-678 (228 cm3 cm−3 at 90 bar) was much higher than those of PCN-668 (168 cm3 cm−3 for PCN-668 and 165 cm3 cm−3 for PCN-668-Cr at 90 bar). The deliverable methane capacity of PCN-678 at 298 K and 65 bar is 147 cm3 cm−3, which was higher than the famous highly stable MOFs such as MOF-74 and PCN-250.28,41,44 In short, the mesoporous MOFs showed better gravimetric methane storage properties, but the microporous MOF exhibited better volumetric methane storage properties. Figure 5 | Gravimetric and volumetric high-pressure methane uptake isotherms of (a and b) PCN-678, (c and d) PCN-668-Fe, and (e and f) PCN-668-Cr. Download figure Download PowerPoint Conclusion We have presented the design and syntheses of two quite stable iron-based MOFs using tetratopic carboxylate ligands with different symmetries. PCN-678, with its higher symmetry linker, is microporous, while PCN-668, with its lower symmetry linker, is mesoporous. In PCN-668, nanoscale cage-like building units coexisted, giving rise to an open, one-dimensional (1D) channel. Due to the reduction of the ligand symmetry, the neighboring cages existed as mutual diastereomers. We improved further the chemical stability of the mesoporous MOF by applying solvent-assisted metal metathesis to PCN-668 to obtain a Cr(III)-based analog. PCN-668-Cr exhibited very high stability to both acidic and basic aqueous solution treatments. Additionally, PCN-678 displayed high volumetric methane storage properties, while PCN-668 exhibited high gravimetric methane uptake properties at room temperature. Our results shed light on the rational design and synthesis of stable microporous and mesoporous MOFs, expanding the growing list of known consequences of their linker symmetry reduction. Supporting Information Supporting Information is available. Conflict of Interest The authors declare no competing financial interests. Acknowledgments The gas sorption studies were supported by the Center for Gas Separations, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (no. DE-SC0001015). Structural analyses were supported by the Robert A. Welch Foundation through a Welch Endowed Chair to H.-C.Z. (A-0030). The National Science Foundation Graduate Research Fellowship (DGE: 1252521) is gratefully acknowledged. The authors also acknowledge the financial support of the U.S. Department of Energy Office of Fossil Energy, National Energy Technology Laboratory (no. DE-FE0026472), and National Science Foundation Small Business Innovation Research (NSF-SBIR) under grant no. (1632486). The authors also acknowledge the financial support of the Strategic Priority Research Program of the Chinese Academy of Sciences (no. XDB20000000), National Nature Science Foundation of China (no. 21871266), CAS (no. QYZDY-SSW-SLH025), and Youth Innovation Promotion Association CAS. References 1. Furukawa H.; Cordova K. E.; O'Keeffe M.; Yaghi O. M.The Chemistry and Applications of Metal-Organic Frameworks.Science2013, 341, 1230444. Google Scholar 2. Kim Y.; Huh S.Pore Engineering of Metal–Organic Frameworks: Introduction of Chemically Accessible Lewis Basic Sites Inside MOF Channels.CrystEngComm2016, 18, 3524–3550. Google Scholar 3. Wen Y.; Zhang J.; Xu Q.; Wu X.-T.; Zhu Q.-L.Pore Surface Engineering of Metal–Organic Frameworks for Heterogeneous Catalysis.Coord. Chem. Rev.2018, 376, 248–276. Google Scholar 4. Chai Y.; Han X.; Li W.; Liu S.; Yao S.; Wang C.; Shi W.; da-Silva I.; Manuel P.; Cheng Y.; Daemen L. D.; Ramirez-Cuesta A. J.; Tang C. C.; Jiang L.; Yang S.; Guan N.; Li L.Control of Zeolite Pore Interior for Chemoselective Alkyne/Olefin Google Scholar Li H.; X.; Liu a Heterogeneous Through of on Metal–Organic Google Scholar S.; Zhou W.; Metal-Organic for Gas Google Scholar L.; M.; W.; Xu Y.; Sites Inside for Energy and Google Scholar Wang H.; S.; S.; Yaghi O. Chemistry of Metal–Organic Google Scholar T. L.; for the and of Google Scholar C. Zhou in Metal-Organic Chem. Google Scholar Yang D.; by Frameworks: Perspective and for Future Google Scholar Wu S.; H.; Shi W.; Cheng Metal-Organic Google Scholar L. O. of Metal-Organic Google Scholar Metal-Organic Frameworks as for Chem. Google Scholar Metal-Organic Frameworks as for and Google Scholar Zhang M.; Zhou W.; K. Liu W.; Y.; Wu H.; Y.; J.; of to and Chem. Google Scholar J.; Wang X.; Yang Y.; Y.; Zhou W.; Li the Pore and Chemistry in Metal-Organic Frameworks for Google Scholar Wu Liu Li T. C. Material with 1, Google Scholar Yuan S.; L.; Wang J.; M.; C.; Y.; Qin J.; Yang X.; Zhang P.; Wang Q.; L.; Zhang Y.; Zhang L.; Y.; Li J.; Zhou Metal-Organic Frameworks: and Google Scholar S.; N.; C.; S.; K. Inorganic Frameworks with Chem. Google Scholar and State Google Scholar Kim M.; H.; K. and in Metal-Organic Chem. Google Scholar Zhang M.; D.; Li L.; Yang Y.; Cai Y.; Zhou MOFs as Google Scholar J.; Yuan S.; Qin J.; Liu C.; C.; Wu M.; Yuan D.; Zhou C.; Hong the Structure of Frameworks Through Chem. Google Scholar Yuan S.; X.; J.; C.; Qin E.; Wang X.; Y.; M.; D.; Liu D.; Zhou and the for MOF 1, Google Scholar Wang D.; Liu T. J.; Yuan S.; P.; M.; X.; Zhou of Chem. Google Scholar D.; Y.; Li Jiang L.; Zhou Metal-Organic Frameworks with Stability as Chem. Google Scholar D.; Wang P.; C. M.; L.; M.; Liu T. S.; Yuan D.; M.; Zhou as a Metal-Organic Google Scholar C. N.; S.; Matzger A. from of Google Scholar J.; A. Matzger A. of a via at Google Scholar K. A. Matzger A. for the of with Chem. Google Scholar J.; Yuan S.; Qin J.; Wu M.; C. Li J.; N.; Li Zhang P.; Zhou a of Metal-Organic Chem. Google Scholar C.; J.; L.; Wu W.; J.; Li of to the Stability of Metal-Organic Google Scholar Wang M.; Y.; Li Metal–Organic Frameworks for the of Chem. Google Scholar P.; J.; M.; Synthesis of Metal-Organic Frameworks: From to Google Scholar S.; I.; A. M.; Synthesis of Google Scholar Furukawa S.; Y.; S.; by and Chem. Google Scholar Wang H.; Zhang Y.; Li M.; S.; Li D.; Zhang A and Metal-Organic Chem. Google Scholar Li P.; Zhang X.; Li P.; C.; O. to with for Chem. Google Scholar Y.; Zhou W.; of Metal–Organic Frameworks with and an for Google Scholar M.; Metal-Organic Frameworks for Gas Google Scholar W.; Yuan D.; T. Li Zhou and Metal-Organic with a 90 Chem. Google Scholar Li Wen M.; Wang H.; Wu H.; M.; Zhou W.; Metal-Organic with Chem. Google Scholar Y.; I.; O. in Metal-Organic Frameworks: and Chem. Google Scholar Zhang Zhou Zhang and Zhang of Chemistry, Information Chinese gas sorption studies were supported by the Center for Gas Separations, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (no. DE-SC0001015). Structural analyses were supported by the Robert A. Welch Foundation through a Welch Endowed Chair to H.-C.Z. (A-0030). The National Science Foundation Graduate Research Fellowship (DGE: 1252521) is gratefully acknowledged. The authors also acknowledge the financial support of the U.S. Department of Energy Office of Fossil Energy, National Energy Technology Laboratory (no. DE-FE0026472), and National Science Foundation Small Business Innovation Research (NSF-SBIR) under grant no. (1632486). The authors also acknowledge the financial support of the Strategic Priority Research Program of the Chinese Academy of Sciences (no. XDB20000000), National Nature Science Foundation of China (no. 21871266), CAS (no. QYZDY-SSW-SLH025), and Youth Innovation Promotion Association CAS.

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