Assembly of an indium–porphyrin framework JLU-Liu7: a mesoporous metal–organic framework with high gas adsorption and separation of light hydrocarbons

Abstract

By reacting with indium nitrate and tetrakis(4-carboxyphenyl)-porphyrin (H₄TCPP), a mesoporous indium–porphyrin framework, named JLU-Liu7, which features a rare (4,4)-connected frl net based on 1D inorganic indium rod SBUs, has been constructed. It exhibits high performance for gas adsorption and light hydrocarbon separation.

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Introduction

In the last three decades, assembly and functionalization of metal–organic frameworks (MOFs) have attracted significant attention. This is not only due to their intriguing varieties of architectural diversity, chemical multiformity and tailorability,¹ but also because of their ground potential applications in storage, carbon dioxide capture, separation, catalysis, drug delivery, and sensing.² Recently, metal–porphyrin frameworks (MPFs) as an important branch of MOFs have been widely investigated for their applications such as guest molecule adsorption and separation, catalysis, nano-thin films and light-harvesting.^1e,3–6 To our knowledge, there are three effective synthetic strategies implemented to construct MPFs: (i) crystal engineering synthesis of MPFs by using porphyrin ligands;^3,4 (ii) pillared-layer construction of MPFs with pyridyl–porphyrin as pillars;⁵ (iii) postsynthetic modification of MPFs. In addition, porphyrin molecules as guest molecules can also be encapsulated into the cavities of MOFs.⁶ The secondary building unit (SBU) strategy as an elementary and the most important synthetic method has been approved to be a triumphant strategy to assemble MOFs.⁷ M(OH)(COO)₂ is a kind of common SBU which is comprised of bi/trivalent metal cations (such as Mg²⁺, Al³⁺, Sc³⁺, V³⁺, Cr³⁺, Mn²⁺, Fe³⁺ and In³⁺), a bridging OH⁻ group and a ligand.^2b,8 Plenty of MOFs based on M(OH)(COO)₂ SBUs have been reported, such as the famous MIL-47^9a and MIL-53 series,^9b In(OH)L (L = C₁₇F₆O₄H₈),^9c JUC-77,^9d In₂(OH)₂(TBAPy),^9e Mg-CPF-1,^9f InOF-1,^9g Al-PMOF,^9h NOTT-300⁹ⁱ and 437-MOF.^9j However, examples of MPFs based on In(OH)(COO)₂ SBU still remain scarce and need to be further developed.

Light hydrocarbons are very essential rare chemicals and energy resources. Separation of propane (C3), ethene and ethane (C2s) from methane (C1) is a very significant industrial process. Recently, scientists have focused on separating light hydrocarbons by using porous MOF materials, which have tunable pore sizes, high surface areas and open metal coordination sites. The famous MOF-74/CPO-27 series reported by Long's group and Snurr's group were exploited to separate light hydrocarbons and demonstrated remarkable performance.¹⁰ In particular, MOF-74-Fe was successfully used in the separation of C₃H₈/C₃H₆ and CH₄/C₂H₂/C₂H₄/C₂H₆.^10b Moreover, some porous MOF materials are promising candidates for application in the separation of light hydrocarbons, such as UTSA-33, UTSA-34 and UTSA-35 reported by Chen's group,¹¹ CID-5/CID-6 reported by Kitagawa's group,¹² MCOF-1/ZnP-CTFs reported by Zhu's group,¹³ FIR-7 reported by Zhang's group,¹⁴ and some part of the JLU-Liu series by our group.¹⁵

Herein, we demonstrate a mesoporous MPF material [In₂(OH)₂(C₄₈H₂₆N₄O₈)]·(DMF)₆(H₂O)₄ (named JLU-Liu7) based on In(OH)(COO)₂ SBU, which exhibits a high gas uptake capacity (such as O₂ and CO₂ at low temperatures, and CO₂, C₂H₄, C₂H₆ and C₃H₈ at room temperature) and separation ability (such as CO₂/CH₄, C₂H₄/CH₄, C₂H₆/CH₄ and especially C₃H₈/CH₄).

Experimental

Materials and methods

All the reagents were obtained from commercial sources and used without further purification. Powder X-ray diffraction (PXRD) data were collected on a Rigaku D/max-2550 diffractometer with CuKα radiation (λ = 1.5418 Å). Elemental analyses were performed on a Perkin-Elmer 2400 element analyzer. Thermogravimetric (TG) analyses were performed on a TGA Q500 thermogravimetric analyzer in the temperature range 35–800 °C under air flow with a heating rate of 5 °C min⁻¹.

Synthesis of JLU-Liu7

A mixture of H₄TCPP (3 mg, 0.004 mmol), In(NO₃)₃·4H₂O (12 mg, 0.025 mmol) and 0.2 mL HNO₃ (0.35 M in DMF) in 1 mL DMF and 1 mL DMSO were sealed in a 20 mL vial, ultrasonically, then heated at 85 °C for 48 h to give purple rod crystals (85% yield based on H₄TCPP). Elemental analysis: Found (wt%) C, 49.47; H, 4.88; N, 8.95. Calcd: C, 50.7; H, 5.0; N, 8.97.

X-ray crystallography

Crystallographic data for JLU-Liu7 were collected on a Bruker X8 Prospector APEX II CCD diffractometer using Cu-K_α (λ = 1.54178 Å) radiation at 100 K. All non-hydrogen atoms were easily found from the difference Fourier map. The structure was solved by direct methods and refined by full-matrix least-squares on F² using version 5.1.¹⁶ All non-hydrogen atoms were refined anisotropically. Since the highly disordered cations and guest molecules were trapped in the channels of JLU-Liu7 and could not be modeled properly, there are “Alert level A” about “Check Reported Molecular Weight” and “VERY LARGE Solvent Accessible VOID(S) in Structure” in the “checkCIF/PLATON report” files for JLU-Liu7. The final formula of JLU-Liu7 was derived from crystallographic data combined with elemental and thermogravimetric analysis data. Crystallographic data for JLU-Liu7 have been deposited with the Cambridge Crystallographic Data Centre. Topology information for the compound was calculated by using TOPOS 4.0.¹⁷

Gas adsorption measurements

Gas sorption isotherm measurements were carried out on a Micromeritics ASAP 2420 and Micromeritics ASAP 2020 instrument. The as-synthesized samples were continuously extracted by Soxhlet extraction with acetone under reflux for 2 days to remove the guest molecules. The purity of the as-synthesized samples and guest-exchanged samples was evaluated using PXRD studies (Fig. S2†). About 110 mg of acetone-exchanged samples were activated at 80 °C for 10 h for adsorption test.

Results and discussion

Solvothermal reaction of In(NO₃)₃·4H₂O and tetrakis(4-carboxyphenyl)-porphyrin (H₄TCPP) in DMF and DMSO at 85 °C for 48 h afforded red rod-shaped crystals of JLU-Liu7. Single crystal X-ray diffraction analysis reveals that JLU-Liu7 crystallizes in the Cmmm space group. There is one crystallographically independent indium atom in the structure, and the In atom is coordinated to six oxygen atoms, four of them at the equatorial sites are supplied by four different H₄TCPP ligands, and the other two oxygen atoms are provided by two axial μ₂trans hydroxide anions (Fig. 1a). The H₄TCPP ligand is unmetalized, which is confirmed by the single crystal X-ray diffraction analysis and UV/Vis solid-state absorption spectra, associated with eight indium atoms (Fig. 1a and S1, ESI†). As shown in Fig. 1b and c, JLU-Liu7 contains one-dimensional channels with dimensions of 5.2 × 10.8 Å along the [001] direction and there exists a pore with a diameter of 3.8 × 29.3 Å along the [100] direction. From one topological point of view, the 1D inorganic indium SBU can be viewed as a zigzag ladder with the points of extension (carboxylate C atoms), meanwhile, the ligand can be seen as a 4-connected node and link to the zigzag ladders to make up a (4,4)-connected network with frl topology (Fig. 1d). From another topological perspective, the ligand can be simplified as a 3-connected node and connect to the zigzag ladders to form a (3,4)-connected network with fry topology (Fig. 1e). The framework of JLU-Liu7 is similar to the Al-MOF based on the infinite Al(OH)(COO)₂ rod SBU and H₄TCPP ligand.¹⁸ Calculation performed using PLATON reveals that the pore volume of JLU-Liu7 is 0.69 cm³ g⁻¹ and the total solvent-accessible volume is equal to 2398.2 ų per unit cell, which accounts for 60% of the cell volume, offering opportunities for gas adsorption.

Fig. 1 Single-crystal structure of JLU-Liu7: (a) topology simplification of the ligand and metal chain; (b) framework of JLU-Liu7 viewed along the [100] direction; (c) framework of JLU-Liu7 viewed along the [001] direction; (d) a schematic representation of the (4,4)-connected frl network; (e) a schematic representation of the (3,4)-connected fry network.

The TGA curve indicates that JLU-Liu7 is stable up to nearly 400 °C (Fig. S5†). The first weight loss of 4% before 100 °C corresponds to the release of four guest H₂O molecules (calcd 4.6%). And the second weight loss of 28% from 100 °C to 250 °C corresponds to the release of six guest DMF molecules (calcd 28%). The framework of JLU-Liu7 starts to collapse with loss of the TCPP⁴⁻ ligand from 400 to 800 °C (found 50%; calcd 50.4%). Moreover, the framework still holds its integrity when immersed in water for one week, which can be proved by the crystallinity in powder X-ray diffraction (PXRD) (Fig. S2†). The extraordinarily stable behaviour indicated that JLU-Liu7 may possess industrial applications in the future.

To investigate the porosity of JLU-Liu7, H₂, N₂ O₂, Ar and CO₂ adsorption experiments at low temperatures were executed (Fig. 2). The total N₂ sorption of JLU-Liu7 is about 363 cm³ g⁻¹ at 77 K and 1 atm (Fig. 2a), having BET and Langmuir surface areas of 879 and 1198 m² g⁻¹, respectively. The measured pore volume from the N₂ sorption is up to 0.56 cm³ g⁻¹. The total Ar sorption of JLU-Liu7 is about 421 cm³ g⁻¹ at 1 atm (Fig. 3), having BET and Langmuir surface areas of 1001 m² g⁻¹ and 1315 m² g⁻¹, respectively.

Fig. 2 Gas isotherms for JLU-Liu7: N₂ (a), H₂ (b) and O₂ (c) at 77 K and 1 atm; CO₂ (d) at 195 K and 1 atm.

Fig. 3 The argon isotherm of JLU-Liu7 at 87 K and 1 atm. Inset: The pore size distribution of JLU-Liu7 calculated by using the DFT method.

The measured pore volume from the Ar sorption is up to 0.57 cm³ g⁻¹. The two experimental pore volumes are similar, but a little less than the theoretical calculating value (0.69 cm³ g⁻¹). The pore size distribution from about 0.66 to 3.79 nm is demonstrated by the fit of the adsorption data using the DFT method (Fig. 3). It shows that there exist two types of pores with diameters of 0.8 nm and 2.85 nm, which are homologous to the crystallographic data after considering the van der Waals radii. Both the N₂ and Ar sorption isotherms are similar to the PCN-222 series^4d and IRMOF-74 series,¹⁹ displaying typical type-IV sorption behaviours and exhibiting a steep increase at the point of P/P₀ = 0.2, which is a characteristic of mesoporous materials. Both the PXRD data and single crystal X-ray diffraction analysis confirm that JLU-Liu7 is an example of mesoporous metal–organic frameworks (Meso-MOFs). The H₂ adsorption isotherm at 77 K displays typical type-I sorption behaviours, showing that the hydrogen sorption volume JLU-Liu7 reaches 163 cm³ g⁻¹ (1.46 wt%) at 77 K and 1 atm (Fig. 2b), which is comparable to those of the reported MOFs. In order to calculate the isosteric heat (Q_st), an H₂ adsorption isotherm at 87 K was also tested (Fig. S6a†). At low coverage, the Q_st of JLU-Liu7 for H₂ is 7.8 kJ mol⁻¹ (Fig. S6b†), which is higher than that of MOF-5 (5.2 kJ mol⁻¹), MIL-100 (6.3 kJ mol⁻¹), HKUST-1 (6.6 kJ mol⁻¹) or Soc-MOF (6.5 kJ mol⁻¹), and comparable to that of SNU-4 and MOF-646.^2e

The O₂ sorption isotherm at 77 K shows typical type-I sorption behaviour (Fig. 2c), showing that the O₂ sorption capacity of JLU-Liu7 is 342 cm³ g⁻¹ (15.3 mmol g⁻¹) at 77 K and 0.19 atm. The O₂ capacity of JLU-Liu7 is pretty high around the reported MOFs, such as PCN-17 (210 cm³ g⁻¹), Cu(BDT) (314 cm³ g⁻¹), SNU-25 (233 cm³ g⁻¹) and Zn(TCNQ-TCNQ)bpy (268 cm³ g⁻¹).²⁰

The CO₂ adsorption isotherm at 195 K shows typical type-I sorption behaviour (Fig. 2d), showing that the CO₂ sorption volume of JLU-Liu7 is 291 cm³ g⁻¹ (13 mmol g⁻¹) at 195 K and 1 atm. The CO₂ adsorption isotherms at 273 and 298 K are obtained to investigate the isosteric heat of adsorption. It is found that the total CO₂ adsorptions of JLU-Liu7 are 113 cm³ g⁻¹ (22.2%, 273 K, 1 atm) and 60 cm³ g⁻¹ (11.8%, 298 K, 1 atm), respectively (Fig. S7a†). The CO₂ capacity of JLU-Liu7 is pretty high around the reported MOFs.^2f The Q_st for JLU-Liu7 was calculated to be 28.7 kJ mol⁻¹ at zero-loading, indicating that there were strong interactions between CO₂ molecules and the host framework of JLU-Liu7 (Fig. S7c†).

The pure component adsorption isotherms for CH₄, C₂H₄, C₂H₆ and C₃H₈ of JLU-Liu7 were tested under ambient conditions to investigate its utilization in the adsorption and separation of small hydrocarbons (C1–C3). The different total gas uptake amounts are CH₄ (34 and 17 cm³ g⁻¹), C₂H₄ (114 and 88 cm³ g⁻¹), C₂H₆ (140 and 107 cm³ g⁻¹), and C₃H₈ (143 and 113 cm³ g⁻¹) at 273 and 298 K under 1 atm, respectively (Fig. S8a–S11a†). At zero-coverage, the Q_st values of CH₄, C₂H₄, C₂H₆ and C₃H₈ are 20.9, 27.5, 34.8 and 28.5 kJ mol⁻¹, respectively, which are estimated from the sorption isotherms at 273 and 298 K (Fig. S8c–S11c†).

In order to examine the separation ability of JLU-Liu7, the gas selectivities of CO₂/CH₄, C₂H₄/CH₄, C₂H₆/CH₄ and C₃H₈/CH₄ in a binary mixture were calculated by using ideal solution adsorbed theory (IAST). The selectivity of CO₂/CH₄ (50% and 50%, 5% and 95%) is 6.9 and 6.5. And the selectivities of C₂H₄/CH₄, C₂H₆/CH₄ and C₃H₈/CH₄ are 23.3, 50.4 and 128.5, respectively (Fig. 4). It is obvious that the selectivity of C₃H₈ over CH₄ is higher than many reported MOFs, such as FIR-7,¹⁴ JLU-Liu5^15a and JLU-Liu18,^15b but lower than JLU-Liu22^15c and JLU-Liu15.^15d

Fig. 4 The adsorption isotherms of CO₂, CH₄, C₂H₄, C₂H₆ and C₃H₈ at 298 K along with the dual-site Langmuir Freundlich (DSLF) fits (a, b); the adsorption selectivity of CO₂/CH₄, C₂H₄/CH₄, C₂H₆/CH₄, and C₃H₈/CH₄ is predicted by IAST at 298 K for JLU-Liu7 (c, d).

Conclusions

In summary, we have successfully synthesized a stable Meso-MPF JLU-Liu7 based on an In(OH)(COO)₂ SBU and porphyrin-containing ligand. The novel framework is constructed by using a 1D inorganic indium chain to form a rare (4,4)-connected frl net. JLU-Liu7 exhibits high adsorption performance for small gases and selectivity for CO₂, C₂H₄, C₂H₆ and C₃H₈ over CH₄. Furthermore, this material may be used for gas storage and purification in the future.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (no. 21373095, 21371067 and 21621001).

Notes and references

1. (a) H. Li, M. Eddaoudi, M. O'Keeffe and O. M. Yaghi, Nature, 1999, 402, 276–279; (b) O. M. Yaghi, M. O'Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi and J. Kim, Nature, 2003, 423, 705–714; (c) J. R. Long and O. M. Yaghi, Chem. Soc. Rev., 2009, 38, 1213–1214; (d) H.-C. Zhou, J. R. Long and O. M. Yaghi, Chem. Rev., 2012, 112, 673–674; (e) T. R. Cook, Y.-R. Zheng and P. J. Stang, Chem. Rev., 2013, 113, 734–777; (f) M. Li, D. Li, M. O'Keeffe and O. M. Yaghi, Chem. Rev., 2014, 114, 1343–1370.
2. (a) R. B. Getman, Y.-S. Bae, C. E. Wilmer and R. Q. Snurr, Chem. Rev., 2011, 112, 703–723; (b) P. Horcajada, R. Gref, T. Baati, P. K. Allan, G. Maurin, P. Couvreur, G. Férey, R. E. Morris and C. Serre, Chem. Rev., 2011, 112, 1232–1268; (c) L. E. Kreno, K. Leong, O. K. Farha, M. Allendorf, R. P. Van Duyne and J. T. Hupp, Chem. Rev., 2011, 112, 1105–1125; (d) J.-R. Li, J. Sculley and H.-C. Zhou, Chem. Rev., 2011, 112, 869–932; (e) M. P. Suh, H. J. Park, T. K. Prasad and D.-W. Lim, Chem. Rev., 2011, 112, 782–835; (f) K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald, E. D. Bloch, Z. R. Herm, T.-H. Bae and J. R. Long, Chem. Rev., 2011, 112, 724–781; (g) M. Yoon, R. Srirambalaji and K. Kim, Chem. Rev., 2011, 112, 1196–1231; (h) H. Wu, Q. Gong, D. H. Olson and J. Li, Chem. Rev., 2012, 112, 836–868; (i) H. Furukawa, K. E. Cordova, M. O'Keeffe and O. M. Yaghi, Science, 2013, 341, 974; (j) Q. Yang, D. Liu, C. Zhong and J.-R. Li, Chem. Rev., 2013, 113, 8261–8323.
3. (a) M. E. Kosal, J.-H. Chou, S. R. Wilson and K. S. Suslick, Nat. Mater., 2002, 1, 118–121; (b) K. S. Suslick, P. Bhyrappa, J. H. Chou, M. E. Kosal, S. Nakagaki, D. W. Smithenry and S. R. Wilson, Acc. Chem. Res., 2005, 38, 283–291; (c) W.-Y. Gao, M. Chrzanowski and S. Ma, Chem. Soc. Rev., 2014, 43, 5841–5866; (d) L. D. DeVries and W. Choe, J. Chem. Crystallogr., 2008, 39, 229–240; (e) F. Cao, M. Zhao, Y. Yu, B. Chen, Y. Huang, J. Yang, X. Cao, Q. Lu, X. Zhang, Z. Zhang, C. Tan and H. Zhang, J. Am. Chem. Soc., 2016, 138, 6924–6927; (f) Q. Lin, X. Bu, A. Kong, C. Mao, X. Zhao, F. Bu and P. Feng, J. Am. Chem. Soc., 2015, 137, 2235–2238; (g) K. Wang, X.-L. Lv, D. Feng, J. Li, S. Chen, J. Sun, L. Song, Y. Xie, J.-R. Li and H.-C. Zhou, J. Am. Chem. Soc., 2016, 138, 914–919.
4. (a) B. J. Burnett, P. M. Barron, C. Hu and W. Choe, J. Am. Chem. Soc., 2011, 133, 9984–9987; (b) C. Y. Lee, O. K. Farha, B. J. Hong, A. A. Sarjeant, S. T. Nguyen and J. T. Hupp, J. Am. Chem. Soc., 2011, 133, 15858–15861; (c) X.-S. Wang, L. Meng, Q. Cheng, C. Kim, L. Wojtas, M. Chrzanowski, Y.-S. Chen, X. P. Zhang and S. Ma, J. Am. Chem. Soc., 2011, 133, 16322–16325; (d) D. Feng, Z.-Y. Gu, J.-R. Li, H.-L. Jiang, Z. Wei and H.-C. Zhou, Angew. Chem., Int. Ed., 2012, 51, 10307–10310; (e) W. Morris, B. Volosskiy, S. Demir, F. Gándara, P. L. McGrier, H. Furukawa, D. Cascio, J. F. Stoddart and O. M. Yaghi, Inorg. Chem., 2012, 51, 6443–6445; (f) H.-L. Jiang, D. Feng, K. Wang, Z.-Y. Gu, Z. Wei, Y.-P. Chen and H.-C. Zhou, J. Am. Chem. Soc., 2013, 135, 13934–13938; (g) Q. Lin, X. Bu, A. Kong, C. Mao, X. Zhao, F. Bu and P. Feng, J. Am. Chem. Soc., 2015, 137, 2235–2238; (h) K. Wang, D. Feng, T.-F. Liu, J. Su, S. I. Yuan, Y.-P. Chen, M. Bosch, X. Zou and H.-C. Zhou, J. Am. Chem. Soc., 2014, 136, 13983–13986; (i) T.-F. Liu, D. Feng, Y.-P. Chen, L. Zou, M. Bosch, S. Yuan, Z. Wei, S. Fordham, K. Wang and H.-C. Zhou, J. Am. Chem. Soc., 2015, 137, 413–419.
5. (a) H.-J. Son, S. Jin, S. Patwardhan, S. J. Wezenberg, N. C. Jeong, M. So, C. E. Wilmer, A. A. Sarjeant, G. C. Schatz, R. Q. Snurr, O. K. Farha, G. P. Wiederrecht and J. T. Hupp, J. Am. Chem. Soc., 2012, 135, 862–869; (b) S. Jin, H.-J. Son, O. K. Farha, G. P. Wiederrecht and J. T. Hupp, J. Am. Chem. Soc., 2013, 135, 955–958.
6. (a) M. H. Alkordi, Y. Liu, R. W. Larsen, J. F. Eubank and M. Eddaoudi, J. Am. Chem. Soc., 2008, 130, 12639–12641; (b) R. W. Larsen, L. Wojtas, J. Perman, R. L. Musselman, M. J. Zaworotko and C. M. Vetromile, J. Am. Chem. Soc., 2011, 133, 10356–10359; (c) Z. Zhang, L. Zhang, L. Wojtas, M. Eddaoudi and M. J. Zaworotko, J. Am. Chem. Soc., 2011, 134, 928–933; (d) Z. Zhang, L. Zhang, L. Wojtas, P. Nugent, M. Eddaoudi and M. J. Zaworotko, J. Am. Chem. Soc., 2011, 134, 924–927; (e) Z. Zhang, W.-Y. Gao, L. Wojtas, S. Ma, M. Eddaoudi and M. J. Zaworotko, Angew. Chem., Int. Ed., 2012, 51, 9330–9334; (f) Z. Zhang, L. Wojtas, M. Eddaoudi and M. J. Zaworotko, J. Am. Chem. Soc., 2013, 135, 5982–5985.
7. (a) J. J. Perry Iv, J. A. Perman and M. J. Zaworotko, Chem. Soc. Rev., 2009, 38, 1400–1417; (b) D. J. Tranchemontagne, J. L. Mendoza-Cortes, M. O'Keeffe and O. M. Yaghi, Chem. Soc. Rev., 2009, 38, 1257–1283; (c) S. Wang, T. Zhao, G. Li, L. Wojtas, Q. Huo, M. Eddaoudi and Y. Liu, J. Am. Chem. Soc., 2010, 132, 18038–18041; (d) S.-T. Zheng, J. T. Bu, Y. Li, T. Wu, F. Zuo, P. Feng and X. Bu, J. Am. Chem. Soc., 2010, 132, 17062–17064; (e) J. F. Eubank, L. Wojtas, M. R. Hight, T. Bousquet, V. C. Kravtsov and M. Eddaoudi, J. Am. Chem. Soc., 2011, 133, 17532–17535.
8. (a) S. Bourrelly, P. L. Llewellyn, C. Serre, F. Millange, T. Loiseau and G. Férey, J. Am. Chem. Soc., 2005, 127, 13519–13521; (b) G. Ferey and C. Serre, Chem. Soc. Rev., 2009, 38, 1380–1399; (c) L. Chen, J. P. S. Mowat, D. Fairen-Jimenez, C. A. Morrison, S. P. Thompson, P. A. Wright and T. Düren, J. Am. Chem. Soc., 2013, 135, 15763–15773.
9. (a) K. Barthelet, J. Marrot, D. Riou and G. Férey, Angew. Chem., Int. Ed., 2002, 41, 281–284; (b) C. Serre, F. Millange, C. Thouvenot, M. Noguès, G. Marsolier, D. Louër and G. Férey, J. Am. Chem. Soc., 2002, 124, 13519–13526; (c) F. Gándara, B. Gomez-Lor, E. Gutiérrez-Puebla, M. Iglesias, M. A. Monge, D. M. Proserpio and N. Snejko, Chem. Mater., 2007, 20, 72–76; (d) Z. Jin, H.-Y. Zhao, X.-J. Zhao, Q.-R. Fang, J. R. Long and G.-S. Zhu, Chem. Commun., 2010, 46, 8612–8614; (e) K. C. Stylianou, R. Heck, S. Y. Chong, J. Bacsa, J. T. A. Jones, Y. Z. Khimyak, D. Bradshaw and M. J. Rosseinsky, J. Am. Chem. Soc., 2010, 132, 4119–4130; (f) Q. Lin, T. Wu, S.-T. Zheng, X. Bu and P. Feng, Chem. Commun., 2011, 47, 11852–11854; (g) J. Qian, F. Jiang, D. Yuan, M. Wu, S. Zhang, L. Zhang and M. Hong, Chem. Commun., 2012, 48, 9696–9698; (h) A. Fateeva, P. A. Chater, C. P. Ireland, A. A. Tahir, Y. Z. Khimyak, P. V. Wiper, J. R. Darwent and M. J. Rosseinsky, Angew. Chem., Int. Ed., 2012, 51, 7440–7444; (i) S. Yang, J. Sun, A. J. Ramirez-Cuesta, S. K. Callear, I. F. DavidWilliam, D. P. Anderson, R. Newby, A. J. Blake, J. E. Parker, C. C. Tang and M. Schröder, Nat. Chem., 2012, 4, 887–894; (j) M. Du, M. Chen, X.-G. Yang, J. Wen, X. Wang, S.-M. Fang and C.-S. Liu, J. Mater. Chem. A, 2014, 2, 9828–9834.
10. (a) Y.-S. Bae, C. Y. Lee, K. C. Kim, O. K. Farha, P. Nickias, J. T. Hupp, S. T. Nguyen and R. Q. Snurr, Angew. Chem., Int. Ed., 2012, 51, 1857–1860; (b) E. D. Bloch, W. L. Queen, R. Krishna, J. M. Zadrozny, C. M. Brown and J. R. Long, Science, 2012, 335, 1606–1610.
11. (a) Y. He, Z. Zhang, S. Xiang, F. R. Fronczek, R. Krishna and B. Chen, Chem. Commun., 2012, 48, 6493–6495; (b) Y. He, Z. Zhang, S. Xiang, F. R. Fronczek, R. Krishna and B. Chen, Chem. – Eur. J., 2012, 18, 613–619; (c) Y. He, Z. Zhang, S. Xiang, H. Wu, F. R. Fronczek, W. Zhou, R. Krishna, M. O'Keeffe and B. Chen, Chem. – Eur. J., 2012, 18, 1901–1904.
12. S. Horike, Y. Inubushi, T. Hori, T. Fukushima and S. Kitagawa, Chem. Sci., 2012, 3, 116–120.
13. (a) H. Ma, H. Ren, S. Meng, Z. Yan, H. Zhao, F. Sun and G. Zhu, Chem. Commun., 2013, 49, 9773–9775; (b) H. Ma, H. Ren, S. Meng, F. Sun and G. Zhu, Sci. Rep., 2013, 3, 2611.
14. Y.-P. He, Y.-X. Tan and J. Zhang, Chem. Commun., 2013, 49, 11323–11325.
15. (a) D. Wang, T. Zhao, Y. Cao, S. Yao, G. Li, Q. Huo and Y. Liu, Chem. Commun., 2014, 50, 8648–8650; (b) D. Wang, B. Liu, S. Yao, T. Wang, G. Li, Q. Huo and Y. Liu, Chem. Commun., 2015, 51, 15287–15289; (c) S. Yao, D. Wang, Y. Cao, G. Li, Q. Huo and Y. Liu, J. Mater. Chem. A, 2015, 3, 16627–16632; (d) X. Luo, L. Sun, J. Zhao, D.-S. Li, D. Wang, G. Li, Q. Huo and Y. Liu, Cryst. Growth Des., 2015, 15, 4901–4907; (e) S. Yao, X. Sun, B. Liu, R. Krishna, G. Li, Q. Huo and Y. Liu, J. Mater. Chem. A, 2016, 4, 15081–15087.
16. G. M. Sheldrick, SHELXTL-NT, version 5.1, Bruker AXS Inc., Madison, WI, 1997.
17. V. A. Blatov, A. P. Shevchenko and D. M. Proserpio, Cryst. Growth Des., 2014, 14, 3576–3683.
18. A. Fateeva, P. A. Chater, C. P. Ireland, A. A. Tahir, Y. Z. Khimyak, P. V. Wiper, J. R. Darwent and M. J. Rosseinsky, Angew. Chem., Int. Ed., 2012, 51, 7440–7444.
19. H. Deng, S. Grunder, K. E. Cordova, C. Valente, H. Furukawa, M. Hmadeh, F. Gándara, A. C. Whalley, Z. Liu, S. Asahina, H. Kazumori, M. O'Keeffe, O. Terasaki, J. F. Stoddart and O. M. Yaghi, Science, 2012, 336, 1018–1023.
20. (a) S. Q. Ma, X. S. Wang, D. Q. Yuan and H.-C. Zhou, Angew. Chem., Int. Ed., 2008, 47, 4130–4133; (b) M. Dincă, A. F. Yu and J. R. Long, J. Am. Chem. Soc., 2006, 128, 8904–8913; (c) Y. E. Cheon, J. Park and M. P. Suh, Chem. Commun., 2009, 36, 5436–5438; (d) S. Shimomura, M. Higuchi, R. Matsuda, K. Yoneda, Y. Hijikata, Y. Kubota, Y. Mita, J. Kim, M. Takata and S. Kitagawa, Nat. Chem., 2010, 2, 633–637.

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Footnote

† Electronic supplementary information (ESI) available: Crystal data and structure refinement, structure information, XRD, TGA, gas adsorption and adsorptive selectivity. CCDC 1443466. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6qi00440g

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