Heterometallic Strategy for Enhancing the Dynamic Separation of

Mar 22, 2019 - Synopsis. A family of heterometallic NbU-3-Mn/MIII compounds was synthesized through postsynthetic exchange of MIII ions of a pentanucl...
0 downloads 0 Views 2MB Size
Download PDF
Communication Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX

pubs.acs.org/IC

Heterometallic Strategy for Enhancing the Dynamic Separation of C2H2/CO2: A Linear Pentanuclear Cluster-Based Metal−Organic Framework Lianyan Jiang, Nana Wu, Qian Li, Jia Li,* Dapeng Wu, and Yanshuo Li School of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, China

Inorg. Chem. Downloaded from pubs.acs.org by UNIV OF ADELAIDE on 03/22/19. For personal use only.

S Supporting Information *

fundamentally important role in the performance of the materials. Considering that, we started to introduce two or more types of metal ions to the MOFs with a certain C2H2/CO2 separation efficiency to construct heteronuclear MOFs to enhance their functions. Herein, we first synthesized a MnII-cluster-based MOF, namely, [Mn 5 (HTATB) 2 (TATB) 2 (H 2 O) 4 ]·6DMF·2H 2 O (NbU-3-Mn, where NbU denotes Ningbo University, with DMF = N,N-dimethylformamide), constructed from a triangular organic linker, 4,4′,4″-s-triazine-2,4,6-tribenzoic acid (H 3 TATB), and linear pentanuclear Mn 5 clusters {Mn5(COO)10(COOH)2(H2O)4} as secondary building units (Figure 1a). In NbU-3, the linear pentanuclear Mn5 clusters can

ABSTRACT: A family of heterometallic NbU-3-Mn/MIII compounds were synthesized through postsynthetic exchange of MIII ions of a pentanuclear MnII-based metal−organic framework (NbU-3-Mn, where NbU denotes Ningbo University) for enhancing the gasseparation performance. Significantly, NbU-3-Mn/Fe has a C2H2/CO2 separation selectivity similar to that of NbU3-Mn but exhibits enhanced dynamic separation of C2H2/ CO2, which was proven by breakthrough experiments.

I

n recent years, research on the structures, properties, and applications of metal−organic frameworks (MOFs) has been a rapidly growing field in chemistry, physics, and materials science.1−3 In various applications of MOF materials, gas separation is a formidable challenge in both academic research and industrial applications. Nonthermally driven separation technology using pore materials has received widespread attention based on the considerations of cost-efficiency and environmental compatibility.4 Extensive research on MOFs has led to a number of new MOF adsorbents whose separation selectivity and capacity have surpassed those of traditional zeolite materials. Up to now, some MOFs have been reported to target the very challenging C2H2/C2H4, C2H4/C2H6, and C3H6/ C3H8 separations.5−7 Among the diverse gas separations, the separation of a C2H2/ CO2 mixture still remains very challenging because the two gas molecules have very similar shapes, dimensions, and boiling points.8 Although several MOFs have been tried for this important mixture separation, the selectivities are still quite low. Moreover, considering that the trade-off between the adsorption capacity and selectivity of porous materials is a major barrier for efficient gas separation, how to simultaneously increase the amount of adsorption and even the stability of the separating materials also encountered a bottleneck. Compared to the separating materials, many strategies have been developed to improve the storage performance of MOFs as adsorbent materials.9−11 For example, heterometallic MOFs can increase the amount of gas adsorption to varying degrees, while enhancing the stability of the materials at the same time. Classic examples are Fe2+- and Cr2+-doped PCN-426-Mg,12 whose N2 adsorption capacities increased significantly. Simultaneously, they can survive after acidic and basic water treatment, and the crystallinity of Cr2+-doped PCN-426-Mg remains intact from extremely acidic conditions (4 M HCl) to pH 12 for at least 12 h. Obviously, the synergistic effect of heterometals plays a © XXXX American Chemical Society

Figure 1. Perspective view of the Mn5 unit with selective atom labels (a) and the 3D porous framework without solvents viewed along the a axis (b). Color code: Mn, green; C, black; O, red; N, blue; irregular cavities, yellow. The H atoms are omitted for clarity.

offer four open-metal sites after thermal activation, and the welldesigned H3TATB ligands carry multiple Lewis basic sites anchoring on the triazine cores in the channels. Then, the heterometallic NbU-3-Mn/MIII (MIII = V, Cr, Fe) compounds were obtained using a two-step process via metal-ion exchange. Other methods, the one-pot solvothermal reactions between the ligand H3TATB and MIII (M = V, Cr, Fe) salts, all failed to yield a crystalline product. Received: January 31, 2019

A

DOI: 10.1021/acs.inorgchem.9b00298 Inorg. Chem. XXXX, XXX, XXX−XXX

Communication

Inorganic Chemistry Single-crystal X-ray diffraction (XRD) studies reveal that compounds NbU-3-Mn crystallize in the monoclinic space group P21/c. As illustrated in Figure 1, the asymmetric unit consists of two and a half crystallographically independent MnII centers, four TATB ligands, and four coordinated H2O molecules. Mn1, located at both ends of the linear pentanuclear Mn5 clusters, is coordinated by two H2O molecules and four O atoms from three deprotonated carboxyl groups and one protonated carboxyl group. Mn2 is located in a distorted octahedral center and coordinated by six carboxylate O atoms from five carboxylate groups. Mn3 is located in the center of the pentanuclear Mn5 clusters and is of an octahedral geometry, with two apical positions occupied by two carboxylate O atoms and four equatorial positions occupied by four O atoms from four carboxylate groups. The pentanuclear MnII cluster is finally bound to four TATB ligands with Mn−O = 2.064(2)−2.291(6) Å and four terminal H2O molecules with Mn−OW = 2.179(17)− 2.181(13) Å (Table S2). Mn−O bond distances all fall in the range of the MnII state, consistent with the results of the bond valence sum (Table S3).13,14 From a topological point of view, each linear pentanuclear {Mn5(COO)10(COOH)2(H2O)4} unit is connected to 12 trigonal TATB ligands, and each trigonal TATB ligand, in turn, links three linear units, thus forming a 3,12-connected 3D framework. More interestingly, the solvent-accessible volume of NbU-3Mn without coordinated DMF molecules and solvent guests is 52.8% per unit cell calculated by PLATON.15 The 3D framework of NbU-3-Mn features intersecting 2D channels and many kinds of irregular cavities calculated by PLATON with the radii between 1.3 and 5.1 Å, indicating that NbU-3-Mn may exhibit excellent adsorption properties. Unfortunately, because of the absence of diffraction points at high angles of the ion-exchangetreated NbU-3-Mn, we were unable to obtain the crystal structure of NbU-3-Mn/MIII. However, a powder XRD study confirmed that heterometallic NbU-3-Mn/MIII compounds are isoreticular to the structure of NbU-3-Mn. Moreover, energydispersive X-ray spectrometry (EDS), measuring the component elements of a single crystal, indicates that each sample contains both Mn2+ and doped metal ions (Figures S4−S6). The EDS results of the Mn/MIII ratios reveal that Fe3+ is the easiest to exchange in NbU-3-Mn, with the highest ratio of Fe/Mn close to 2/3, whereas the observed V/Mn and Cr/Mn ratios are only about 1/4 and 1/7. In addition, the thermal stabilities of the heterometallic NbU-3-Mn/MIII compounds have been greatly improved, as predicted. Prior to gas measurement, the acetonitrile-exchanged NbU-3Mn compounds were first freeze-dried for 24 h in a lyophilizer and then degassed at room temperature under a dynamic vacuum for another 24 h to give fully activated samples. Because of the higher stability of the heterometallic NbU-3-Mn/MIII compounds, the acetonitrile-exchanged samples can be activated at 80 °C. As shown in Figure S5, the stabilities of all activated NbU-3 have been verified by a powder XRD study. The N2 adsorption and desorption isotherms of activated NbU-3 at 77 K all exhibit reversible type I sorption behavior (Figure 2). The corresponding Langmuir and Brunauer−Emmett−Teller surface areas were estimated to vary from 235 to 784 cm3 g−1 and from 140 to 551 cm3 g−1, respectively. In order to probe the potential applications of NbU-3 for the industrial gas separation, single-component adsorption isotherms of all activated NbU-3 for C2 light hydrocarbons and CO2 were measured at 273 and 298 K, respectively (Figure 3). The C2H2 and CO2 uptakes by NbU-3 follow the trend Fe/Mn

Figure 2. N2 sorption isotherms for NbU-3 at 77 K.

≈ Cr/Mn > V/Mn > Mn, while for C2H4 and C2H6, the adsorption capacities have a tendency of Cr/Mn > Fe/Mn > V/ Mn > Mn. Clearly, MIII-doped samples exhibit varying degrees of enhanced adsorption capacity. At zero loading, the adsorption heat value for C2Hx and CO2 of NbU-3 were estimated from the sorption isotherms at 273 and 298 K using the virial equation (Figure S27). Notably, NbU-3-Mn/Fe almost has the lowest isosteric heat of both C2 light hydrocarbons, while the homometallic NbU-3-Mn has the highest C2H2 isosteric heat; this value is remarkable, higher than those of all reported MOFs16−18 containing open-metal sites, uncoordinated N atoms, and amino groups, and similar to those of MOF-74-Co (45 kJ mol−1) and MOF-74-Fe (46 kJmol−1).19 The isosteric heat for CO2 for NbU-3-Mn/MIII followed the order of V/Mn > Fe/Mn > Cr/Mn ≈ Mn; this result is in good agreement with the reported CPM-200-Mg/MIII for the adsorption of CO2.20 In our opinion, diversification of the adsorption performance may be related to changes in the framework charge and concentration of charge-balancing anions and may also be related to electrostatic interactions and pore-volume changes. The C2H2 uptakes are ∼2 times greater than those of CO2 and C2H4 for NbU-3, which indicates that NbU-3 shows promise for the highly selective separation of C2H2 over CO2 and C2H4. To evaluate the gas-separation ability, the separation ratios of 50/50 for C2H2/CO2 and C2H2/C2H4 binary mixtures were calculated by ideal adsorbed solution theory (IAST).21 As is shown in Figure 4a, the separation selectivities for C2H2/CO2 under initial pressure are slightly different, with values of 6.8 (V/Mn), 7.8 (Fe/Mn), 6.6 (Cr/Mn), and 8.1 (Mn) at 273 K, respectively. Note that the selectivity value of homometallic NbU-3-Mn is higher than those of materials such as HKUST-1 and NOTT101a. In our opinion, the main reason for inducing the highest selective adsorption of C2H2/CO2 for NbU-3-Mn mainly due to the thermodynamics factor, consistent with the values of the adsorption heat following the trend of C2H2 ≫ C2H4 > CO2 > C2H6, suggests that the open-metal sites hanging on the Mn3 and uncoordinated N sites in the channels synergistically provide divergent host−guest interactions and C2H2 has much stronger interactions with the framework than other gases. Unfortunately, we cannot obtain the gas-loaded crystal structures because of the poor diffraction intensity of the single crystal after the removal of guest molecules. Furthermore, for the separation selectivity for C2H2/C2H4 binary mixtures under initial pressure, NbU-3-Mn/Fe has a relatively high separation ratio of 2.7, even higher than that of NOTT-300,22 indicating possible applications in the industrial separation of acetylene/ ethylene. B

DOI: 10.1021/acs.inorgchem.9b00298 Inorg. Chem. XXXX, XXX, XXX−XXX

Communication

Inorganic Chemistry

Figure 3. Single-component adsorption isotherms of C2H2 (a), CO2 (b), C2H4 (c), and C2H6 (d) for NbU-3-Mn and heterometallic NbU-3-Mn/MIII at 273 K and 1 atm.

Figure 4. IAST adsorption selectivity of 50/50 C2H2/CO2 (a) and C2H2/C2H4 (b) binary mixtures. Experimental column breakthrough curves for C2H2/CO2 separations with NbU-3-Mn (c) and NbU-3-MnFe(d) at 273 K and 1 atm.

Considering that the adsorption amount and selectivity are all important factors in the gas-separation process, experimental breakthrough studies for the C2H2/CO2 mixtures had been carried out with the fully activated NbU-3-Mn and NbU-3MnFe to study the actual separation processes (Figure 4). An equal molar amount of mixed gas passes through a stainless steel column at a flow rate of 1.0 mL min−1, and a highly efficient separation for NbU-3-MnFe was indeed realized, while a negligible separation performance for NbU-3-Mn was found.

Obviously, the adsorption capacity directly determines the effectiveness of gas separation. At 273 K, the breakthrough time of C2H2 is approximately 10.0 min, which represents about 12.5 cm3 of C2H2 being retained per 1 g of NbU-3-MnFe under these dynamic conditions. In conclusion, a family of linear pentanuclear cluster-based heterometallic MOFs (NbU-3-Mn/MIII) with noninterpenetrated structures have been obtained through postsynthetic exchange of MIII ions. Although the C2H2/CO2 separation C

DOI: 10.1021/acs.inorgchem.9b00298 Inorg. Chem. XXXX, XXX, XXX−XXX

Communication

Inorganic Chemistry

Assembly of Two Heteropolynuclear Clusters with Tunable AgI:ZnII Ratio. Inorg. Chem. 2016, 55, 4757−4763. (3) (a) Lee, J. Y.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. B. T.; Hupp, J. T. Metal−organic framework materials as catalysts. Chem. Soc. Rev. 2009, 38, 1450−1459. (b) Deng, Y.-K.; Su, H.-F.; Xu, J.-H.; Wang, W.-G.; Kurmoo, M.; Lin, S.-C.; Tan, Y.-Z.; Jia, J.; Sun, D.; Zheng, L.-S. Hierarchical Assembly of a {MnII15MnIII4} Brucite Disc: Stepby-Step Formation and Ferrimagnetism. J. Am. Chem. Soc. 2016, 138, 1328−1334. (c) Guo, L.-Y.; Su, H.-F.; Kurmoo, M.; Tung, C.-H.; Sun, D.; Zheng, L.-S. Core−Shell {Mn7⊂(Mn,Cd)12} Assembled from Core {Mn7} Disc. J. Am. Chem. Soc. 2017, 139, 14033−14036. (4) (a) Li, J. R.; Sculley, J.; Zhou, H. C. Metal−Organic Frameworks for Separations. Chem. Rev. 2012, 112, 869−932. (b) Jiang, M.; Cui, X.; Yang, L.; Yang, Q.; Zhang, Z.; Yang, Y.; Xing, H. B. A thermostable anion-pillared metal-organic framework for C2H2/C2H4 and C2H2/ CO2 separations. Chem. Eng. J. 2018, 352, 803−810. (5) (a) Cui, X.; Chen, K. J.; Xing, H. B.; Yang, Q. W.; Krishna, R.; Bao, Z. B.; Wu, H.; Zhou, W.; Dong, X. L.; Han, Y.; Li, B.; Ren, Q. L.; Zaworotko, M. J.; Chen, B. L. Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene. Science 2016, 353, 141−144. (b) Hu, T. L.; Wang, H.; Li, B.; Krishna, R.; Wu, H.; Zhou, W.; Zhao, Y.; Han, Y.; Wang, X.; Zhu, W.; Yao, Z.; Xiang, S.; Chen, B. Microporous metal−organic framework with dual functionalities for highly efficient removal of acetylene from ethylene/acetylene mixtures. Nat. Commun. 2015, 6, 7328. (c) Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Hydrocarbon Separations in a Metal-Organic Framework with Open Iron(II) Coordination Sites. Science 2012, 335, 1606−1610. (d) Xu, H.; Cai, J. F.; Xiang, S. C.; Zhang, Z. J.; Wu, C. D.; Rao, X. T.; Cui, Y. J.; Yang, Y.; Krishna, R.; Chen, B. L.; Qian, G. D. A cationic microporous metal−organic framework for highly selective separation of small hydrocarbons at room temperature. J. Mater. Chem. A 2013, 1, 9916−9921. (e) Zhang, J. P.; Chen, X. M. Optimized Acetylene/Carbon Dioxide Sorption in a Dynamic Porous Crystal. J. Am. Chem. Soc. 2009, 131, 5516−5521. (6) (a) Rao, X. T.; Cai, J. F.; Yu, J. C.; He, Y. B.; Wu, C. D.; Zhou, W.; Yildirim, T.; Chen, B. L.; Qian, G. D. A microporous metal−organic framework with both open metal and Lewis basic pyridyl sites for high C2H2 and CH4 storage at room temperature. Chem. Commun. 2013, 49, 6719−6721. (b) Xu, H.; He, Y.; Zhang, Z.; Xiang, S.; Cai, J.; Cui, Y.; Yang, Y.; Qian, G.; Chen, B. A microporous metal−organic framework with both open metal and Lewis basic pyridyl sites for highly selective C2H2/CH4 and C2H2/CO2 gas separation at room temperature. J. Mater. Chem. A 2013, 1, 77−81. (c) Liu, K.; Ma, D. X.; Li, B. Y.; Li, Y.; Yao, K. X.; Zhang, Z. J.; Han, Y.; Shi, Z. High storage capacity and separation selectivity for C2 hydrocarbons over methane in the metal− organic framework Cu−TDPAT. J. Mater. Chem. A 2014, 2, 15823− 15828. (d) Pang, J. D.; Jiang, F. L.; Wu, M. Y.; Liu, C. P.; Su, K. Z.; Lu, W. G.; Yuan, D. Q.; Hong, M. C. A porous metal-organic framework with ultrahigh acetylene uptake capacity under ambient conditions. Nat. Commun. 2015, 6, 7575. (7) (a) Cadiau, A.; Adil, K.; Bhatt, P. M.; Belmabkhout, Y.; Eddaoudi, M. A metal-organic framework−based splitter for separating propylene from propane. Science 2016, 353, 137−140. (b) Liao, P. Q.; Huang, N.Y.; Zhang, W.-X.; Zhang, J.-P.; Chen, X.-M. Controlling guest conformation for efficient purification of butadiene. Science 2017, 356, 1193−1196. (8) (a) Zhang, Z.; Xiang, S.; Chen, B. Microporous metal−organic frameworks for acetylene storage and separation. CrystEngComm 2011, 13, 5983. (b) Matsuda, R.; Kitaura, R.; Kitagawa, S.; Kubota, Y.; Belosludov, R. V.; Kobayashi, T. C.; Sakamoto, H.; Chiba, T.; Takata, M.; Kawazoe, Y.; Mita, Y. Highly controlled acetylene accommodation in a metal−organic microporous material. Nature 2005, 436, 238. (c) Xu, H.; He, Y.; Zhang, Z.; Xiang, S.; Cai, J.; Cui, Y.; Yang, Y.; Qian, G.; Chen, B. A microporous metal−organic framework with both open metal and Lewis basic pyridyl sites for highly selective C2H2/CH4 and C2H2/CO2 gas separation at room temperature. J. Mater. Chem. A 2013, 1, 77−81. (d) Zhang, J.-W.; Hu, M.-C.; Li, S.-N.; Jiang, Y.-C.; Qu, P.; Zhai, Q.-G. Assembly of [Cu2(COO)4] and [M3(u3-O)(COO)6] (M = Sc, Fe, Ga, and In) building blocks into porous frameworks towards

selectivity (by IAST calculation) of the heterometallic material was not improved compared to that of homometallic NbU-3Mn, the stability and adsorption capacity of the series of heterometallic compounds were all greatly improved. Significantly, NbU-3-Mn/Fe has a separation selectivity C2H2/CO2 similar to that of NbU-3-Mn but exhibits enhanced dynamic separation of C2H2/CO2; the different dynamic separation performances of C2H2/CO2 mixtures by the two materials were demonstrated by breakthrough experiments.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.9b00298. Information of materials and measurements, synthetic details, supplementary figures, elemental analysis, thermogavimetric analysis, XRD, IR, EDS, and selected bond and structural parameters (PDF) Accession Codes

CCDC 1876116 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_ [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Jia Li: 0000-0002-8392-1125 Yanshuo Li: 0000-0002-7722-7962 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We gratefully acknowledge the National Natural Science Foundation of China (Grant 21701091), the Open Project of the State Key Laboratory of Physical Chemistry of the Solid Surface (Xiamen University; Grant 201707), and the K. C. Wong Magna Fund at Ningbo University. The authors also thank Prof. Jun Tao and Zi-Shuo Yao from Beijing Institute of Technology for their help in single-crystal testing and analysis.

■

REFERENCES

(1) Kirchon, A.; Feng, L.; Drake, H. F.; Joseph, E. A.; Zhou, H. C. From fundamentals to applications: a toolbox for robust and multifunctional MOF materials. Chem. Soc. Rev. 2018, 47, 8611−8638. (2) (a) Pang, J.; Yuan, S.; Qin, J.; Wu, M.; Lollar, C. T.; Li, J.; Huang, N.; Li, B.; Zhang, P.; Zhou, H. C. Enhancing Pore-Environment Complexity Using a Trapezoidal Linker: Toward Stepwise Assembly of Multivariate Quinary Metal−Organic Frameworks. J. Am. Chem. Soc. 2018, 140, 12328−12332. (b) Wang, Y. J.; Zhou, Y. Y.; Hao, H. G.; Song, M.; Zhang, N.; Yao, S.; Yan, J. H.; Zhang, Z. M.; Lu, T. B. Capped Polyoxometalate Pillars between Metal−Organic Layers for Transferring a Supramolecular Structure into a Covalent 3D Framework. Inorg. Chem. 2018, 57, 1342−1349. (c) Yan, A. X.; Yao, S.; Li, Y. G.; Zhang, Z. M.; Lu, Y.; Chen, W. L.; Wang, E. B. Incorporating Polyoxometalates into a Porous MOF Greatly Improves Its Selective Adsorption of Cationic Dyes. Chem. - Eur. J. 2014, 20, 6927−6933. (d) Wang, Z.; Zhuang, G.-L.; Deng, Y.-K.; Feng, Z.-Y.; Cao, Z.-Z. M.; Kurmoo; Tung, C.-H.; Sun, D. Near-Infrared Emitters: Stepwise D

DOI: 10.1021/acs.inorgchem.9b00298 Inorg. Chem. XXXX, XXX, XXX−XXX

Communication

Inorganic Chemistry ultra-high C2H2/CO2 and C2H2/CH4 separation performance. Chem. Commun. 2018, 54, 2012−2015. (9) (a) Duan, J. G.; Higuchi, M.; Zheng, J. J.; Noro, S. I.; Chang, I. Y.; Hyeon-Deuk, K.; Mathew, S.; Kusaka, S.; Sivaniah, E.; Matsuda, R.; Sakaki, S.; Kitagawa, S. Density Gradation of Open Metal Sites in the Mesospace of Porous Coordination Polymers. J. Am. Chem. Soc. 2017, 139, 11576−11583. (b) Xiang, S. C.; Zhou, W.; Gallegos, J. M.; Liu, Y.; Chen, B. L. Exceptionally High Acetylene Uptake in a Microporous Metal−Organic Framework with Open Metal Sites. J. Am. Chem. Soc. 2009, 131, 12415−12419. (c) Xiang, S. C.; Zhou, W.; Zhang, Z. J.; Green, M. A.; Liu, Y.; Chen, B. L. Open Metal Sites within Isostructural Metal−Organic Frameworks for Differential Recognition of Acetylene and Extraordinarily High Acetylene Storage Capacity at Room Temperature. Angew. Chem., Int. Ed. 2010, 49, 4615−4618. (10) (a) Xue, Y. S.; He, Y. B.; Ren, S. B.; Yue, Y. F.; Zhou, L.; Li, Y. Z.; Du, H. B.; You, X. Z.; Chen, B. L. A robust microporous metal−organic framework constructed from a flexible organic linker for acetylene storage at ambient temperature. J. Mater. Chem. 2012, 22, 10195− 10199. (b) He, Y. B.; Chen, F. L.; Li, B.; Qian, G. D.; Zhou, W.; Chen, B. L. Porous metal−organic frameworks for fuel storage. Coord. Chem. Rev. 2018, 373, 167−198. (c) Zhang, M. X.; Li, B.; Li, Y. Z.; Wang, Q.; Zhang, W. W.; Chen, B. L.; Li, S. H.; Pan, Y.; You, X. Z.; Bai, J. F. Finely tuning MOFs towards high performance in C2H2 storage: synthesis and properties of a new MOF-505 analogue with an inserted amide functional group. Chem. Commun. 2016, 52, 7241−7244. (11) (a) Yang, S. H.; Ramirez-Cuesta, A. J.; Newby, R.; Garcia-Sakai, V.; Manuel, P.; Callear, S. K.; Campbell, S. I.; Tang, C. C.; Schröder, M. Supramolecular binding and separation of hydrocarbons within a functionalized porous metal−organic framework. Nat. Chem. 2015, 7, 121−129. (b) Matsuda, R.; Kitaura, R.; Kitagawa, S.; Kubota, Y.; Belosludov, R. V.; Kobayashi, T. C.; Sakamoto, H.; Chiba, T.; Takata, M.; Kawazoe, Y.; Mita, Y. Highly controlled acetylene accommodation in a metal−organic microporous material. Nature 2005, 436, 238−241. (c) Samsonenko, D. G.; Kim, H.; Sun, Y.; Kim, G. H.; Lee, H. S.; Kim, K. Microporous Magnesium and Manganese Formates for Acetylene Storage and Separation. Chem. - Asian J. 2007, 2, 484−488. (d) Xu, H.; Cai, J. F.; Xiang, S. C.; Zhang, Z. J.; Wu, C. D.; Rao, X. T.; Cui, Y. J.; Yang, Y.; Krishna, R.; Chen, B. L.; Qian, G. D. A cationic microporous metal−organic framework for highly selective separation of small hydrocarbons at room temperature. J. Mater. Chem. A 2013, 1, 9916− 9921. (e) Zhang, J. P.; Chen, X. M. Optimized Acetylene/Carbon Dioxide Sorption in a Dynamic Porous Crystal. J. Am. Chem. Soc. 2009, 131, 5516−5521. (12) (a) Liu, T.-F.; Zou, L.; Feng, D.; Chen, Y.-P.; Fordham, S.; Wang, X.; Liu, Y.; Zhou, H.-C. Stepwise Synthesis of Robust Metal−Organic Frameworks via Postsynthetic Metathesis and Oxidation of Metal Nodes in a Single-Crystal to Single-Crystal Transformation. J. Am. Chem. Soc. 2014, 136, 7813−7816. (b) Zhu, X.-W.; Zhou, X.-P.; Li, D. Exceptionally water stable heterometallic gyroidal MOFs: tuning the porosity and hydrophobicity by doping metal ions. Chem. Commun. 2016, 52, 6513−6516. (13) BRESE, N. E.; O’KEEFFE, M. Bond-Valence Parameters for Solids. Acta Crystallogr., Sect. B: Struct. Sci. 1991, B47, 192−197. (14) Liu, W.; Thorp, H. H. Bond valence sum analysis of metal-ligand bond lengths in metalloenzymes and model complexes. 2. Refined distances and other enzymes. Inorg. Chem. 1993, 32, 4102−4105. (15) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht University: Utrecht, The Netherlands, 2001. (16) Wen, H. M.; Wang, H. Z.; Li, B.; Cui, Y.; Wang, H.; Qian, G.; Chen, B. A Microporous Metal−Organic Framework with Lewis Basic Nitrogen Sites for High C2H2 Storage and Significantly Enhanced C2H2/CO2 Separation at Ambient Conditions. Inorg. Chem. 2016, 55, 7214−7218. (17) Hao, H.-G.; Zhao, Y.-F.; Chen, D. M.; Yu, J.-M.; Tan, K.; Ma, S. Q.; Chabal, Y.; Zhang, Z. M.; Dou, J.-M.; Xiao, Z. H.; Day, G.; Zhou, H. C.; Lu, T. B. Simultaneous Trapping of C2H2 and C2H6 from a Ternary Mixture of C2H2/C2H4/C2H6 in a Robust Metal−Organic Framework for the Purification of C2H4. Angew. Chem., Int. Ed. 2018, 57, 16067− 16071.

(18) Foo, M. L.; Matsuda, R.; Hijikata, Y.; Krishna, R.; Sato, H.; Horike, S.; Hori, A.; Duan, J.; Sato, Y.; Kubota, Y.; Takata, M.; Kitagawa, S. An Adsorbate Discriminatory Gate Effect in a Flexible Porous Coordination Polymer for Selective Adsorption of CO2 over C2H2. J. Am. Chem. Soc. 2016, 138, 3022−3030. (19) Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Hydrocarbon Separations in a Metal-Organic Framework with Open Iron(II) Coordination Sites. Science 2012, 335, 1606. (20) Zhai, Q. G.; Bu, X.; Mao, C.; Zhao, X.; Feng, P. Systematic and Dramatic Tuning on Gas Sorption Performance in Heterometallic Metal−Organic Frameworks. J. Am. Chem. Soc. 2016, 138, 2524−2527. (21) (a) Myers, A. L.; Prausnitz, J. M. Thermodynamics of mixed-gas adsorption. AIChE J. 1965, 11, 121. (b) Krishna, R.; Long, J. R. Screening Metal−Organic Frameworks by Analysis of Transient Breakthrough of Gas Mixtures in a Fixed Bed Adsorber. J. Phys. Chem. C 2011, 115, 12941. (22) Yang, S.; Ramirez-Cuesta, A. J.; Newby, R.; Garcia-Sakai, V.; Manuel, P.; Callear, S. K.; Campbell, S. I.; Tang, C. C.; Schröder, M. Supramolecular binding and separation of hydrocarbons within a functionalized porous metal-organic framework. Nat. Chem. 2015, 7, 121−129.

E

DOI: 10.1021/acs.inorgchem.9b00298 Inorg. Chem. XXXX, XXX, XXX−XXX