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Cite this: Chem. Commun., 2013, 49, 11433 Received 30th September 2013, Accepted 14th October 2013
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Assembly of a unique octa-nuclear copper cluster-based metal–organic framework with highly selective CO2 adsorption over N2 and CH4† Jiahuan Luo, Jing Wang, Guanghua Li, Qisheng Huo and Yunling Liu*
DOI: 10.1039/c3cc47462c www.rsc.org/chemcomm
By using 4-(pyrimidin-5-yl) benzoic acid (4-PmBC) as a ligand, a porous metal–organic framework based on unique octa-nuclear copper clusters was constructed, which exhibited highly selective CO2 uptake over N2 and CH4.
Assembly and functionalization of metal–organic frameworks (MOFs) are fascinating and significant topics in crystal engineering. Numerous MOFs have been reported not only because of their intriguing varieties of architectures and topologies,1 but also due to their potential applications in carbon dioxide capture,2 gas storage,3 separation4 and catalysis.5 Implementation of secondary building units (SBUs) as a basic and most important synthetic method, which is based on poly-nuclear metal clusters linked with numerous organic ligands, has permitted the successful assembly of MOFs.6 Plenty of MOFs have been reported mainly based on fascinating bi-nuclear, tri-nuclear, tetra-nuclear, and hexa-nuclear SBUs, such as HKUST-1 with Cu2(OH)2(CO2)4 units,7 MIL-100 and MIL-101 with Cr3O(OH)3(CO2)6 units,8 MOF-5 with Zn4O(CO2)6 units,9 and MOFs constructed from the rare Cu4Cl units,10 Yb4O units11 and Zr6O4(OH)4(CO2)12 units.12 Recently, MOFs based on a series of rare-earth metal clusters RE6(OH)8(CO2)6(CN4)6 and RE6(OH)8(CO2)12 were reported by Eddaoudi’s group.13 With the progress of human society and industry, a great amount of CO2 emissions caused by human-induced consumption are changing the climate, which has become a major and serious topic of environmental science. One of the urgent tasks to benefit today’s energy and environment is to reduce CO2 emissions. Carbon capture and storage (CCS) is one technical solution found by scientists to reduce CO2 emissions and prevent climate change.14 Thus, discovery of new materials is the core of the CCS technology. Porous materials as the newly developing materials State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China. E-mail: [email protected]; Fax: +86-431-85168624; Tel: +86-431-85168614 † Electronic supplementary information (ESI) available: Materials and methods, crystal data and structure refinement, structure information, IR spectrum, TGA, XRD, N2 isotherm, H2 isotherm and CO2:CH4 selec tivity. CCDC 947183. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/ c3cc47462c
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have been researched by scientists for CO2 capture, such as carbon-based material,15 zeolites,16 ZIFs,17 COFs,18 PPNs,19 PAFs,20 MOFs,21 and so on. Of all porous materials, MOFs have many advantages such as abundant topological structures, designability, regulation of the structure, high specific surface area and low density, which make this type of material extremely promising for CO2 capture and separation. Herein, we report the synthesis, structure and gas adsorption properties of a novel MOF [Cu4(OH)(SO4)3(4-PmBC)(DMF)]0.5DMF 3H2O (JLU-Liu1) based on a unique octa-nuclear copper SBU, which exhibits highly selective CO2 uptake over N2 and CH4. Solvothermal reaction of CuSO45H2O and 4-PmBC in DMF at 115 1C for 24 h afforded green block-shaped crystals of JLU-Liu1;‡ single crystal X-ray diffraction analysis reveals that JLU-Liu1 crystallizes in the P43212 space group.§ There are four crystallographically independent copper atoms in the structure which exhibit four different coordination states (Fig. 1a and Fig. S1a, ESI†). Both Cu1 and Cu4 are four-connected, meanwhile Cu2 and Cu3 are fiveconnected. Cu1 is bonded with two central m4-oxygen atoms and two
Fig. 1 Single-crystal structure of JLU-Liu1 showing the 4-PmBC SBU, which can be viewed as a 3-connected node (red) and the octa-nuclear copper SBU, which can be simplified to a 6-connected node (green) (a); a schematic representation of the ant net (b); framework of JLU-Liu1 viewed along the [111] direction (c).
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Communication oxygen atoms supplied by sulfate ions while Cu4 is linked to one sulfate ion, one DMF molecule, one oxygen atom and one nitrogen atom of the 4-PmBC ligand. Cu2 is connected to four sulfate ions and one nitrogen atom of the 4-PmBC ligand, whereas Cu3 is associated with one central m4-oxygen atom, three oxygen atoms of three sulfate ions and an oxygen atom of the 4-PmBC ligand. There are six sulfate ions exhibiting three-connected coordination states (Fig. S1b, ESI†). Four copper atoms (Cu2, Cu3, Cu4 and Cu4) are connected to two oxygen atoms and two nitrogen atoms of the 4-PmBC ligand (Fig. S1c, ESI†). Around the central core of the two m4-oxygen atoms, the octanuclear copper cluster is made up of six sulfate ions and eight copper atoms. The octa-nuclear copper cluster, which is connected with six 4-PmBC ligands and two DMF molecules, can be simplified to be a 6-connected node (Fig. 1a). And the ligand 4-PmBC coordinates with three copper clusters that can be seen as a 3-connected node (Fig. 1a). Consequently, the structure of JLU-Liu1 can be described as a 3,6-connected network (Fig. 1b), which belongs to mineral-like ant topology. In the framework, there exist one-dimensional channels with dimensions 3.45 4.03 Å, after considering the van der Waals radii, running along the [111] direction (Fig. 1c). More interestingly, the distortion of the 4-PmBC ligands leads to the crystallization of JLU-Liu1 in the chiral space group P43212 which possesses four types of helices. Two opposite helices along the [001] direction intersect at the copper clusters to form a double helical chain (Fig. S2a, ESI†), and these two helical chains can be viewed as four copper clusters linked by ligands arranged in a clockwise/anticlockwise direction to generate two helices with a pitch of 42.2 Å. While other two helices along the [110] direction can be viewed as two copper clusters linked by two ligands and arranged in the clockwise–anticlockwise direction to generate a left-handed helix and a right-handed helix with a pitch of 19.31 Å (Fig. S2b, ESI†). Calculation performed using PLATON22 reveals a total solventaccessible volume equal to 3544.7 Å3 per unit cell, which accounts for 45.1% of the cell volume, offering possibilities for gas adsorption. The thermal stability of JLU-Liu1 has been measured by thermogravimetric analysis (TGA) and variable-temperature powder X-ray diffraction (VTXRD). The TGA curve (Fig. S5, ESI†) and the VTXRD patterns (Fig. S6, ESI†) indicate that JLU-Liu1 is stable up to 260 1C. The first weight loss of 17.5% from 30 to 260 1C corresponds to the loss of half a guest DMF molecule, three H2O guest molecules and one coordinated DMF molecule (calcd. 17.7%). The framework of JLU-Liu1 begins to collapse with loss of the 4-PmBC1 ligand, one central OH ions and three SO42 ions from 260 to 800 1C (found 54.6%; calcd. 54.8%). Gas adsorption studies were executed with the activated JLU-Liu1 sample to test its permanent porosity. The as-synthesized samples were immersed in methanol, acetone, dichloromethane, and acetonitrile solvents for 24 hours, respectively, to remove the high boiling point DMF and H2O guest molecules as the samples we treated before.23,24 The phase purity of the guest-exchanged samples was evaluated using X-ray powder diffraction studies (Fig. S7, ESI†). About 110 mg of dichloromethane-exchanged sample was activated at 80 1C for 10 h for the adsorption test. We executed four different gas adsorption experiments to investigate the porosity of JLU-Liu1, including N2, H2, CH4 and 11434
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Fig. 2
CO2, N2 and CH4 adsorption isotherms of JLU-Liu1 at 298 K.
CO2 gases. The resulting isotherms are shown in Fig. 2. The N2 gas sorption isotherm measured at 77 K (Fig. S8, ESI†) shows that the activated JLU-Liu1 almost cannot adsorb N2 (0.065 cm3 g1). It reveals that N2 molecules hardly enter the 1D channels of the framework; the adsorption happens on the external surface of the material. The total H2 uptake of JLU-Liu1 at 77 K is 38 cm3 g1 (Fig. S9, ESI†). The CH4 adsorption isotherm measured at 298 K reveals that the activated JLU-Liu1 scarcely adsorbs CH4 (0.5 cm3 g1). However, the activated JLU-Liu1 exhibits CO2 adsorption. The total CO2 uptake of the activated JLU-Liu1 at 298 K is 34.7 cm3 g1. This result can be attributed to the difference in the kinetic diameters of probe gases, such as CO2 (3.30 Å), N2 (3.64 Å) and CH4 (3.76 Å).2 There are 1D channels along the [111] direction in the framework of JLU-Liu1; the uncoordinated oxygen atoms of the sulfate ion are arrayed along the inner wall of the channels. The distance between two nearest opposite oxygen atoms is 3.45 Å (considering van der Waals radii of oxygen), which is smaller than the kinetic diameters of N2 and CH4. The N2 and CH4 molecules are limited from entering the channels, however the H2 (the kinetic diameter of 2.89 Å) and CO2 molecules are not restricted. The H2 uptake is pretty low compared to CO2; this result confirms that different interactions between copper and gases are one of the reasons for high CO2 selective adsorption. As mentioned above, the probable reasons for the high selective adsorption of CO2 over N2 and CH4 gases should be attributed to a cooperative effect of the size exclusion and different host–guest interactions.4 The CO2 adsorption isotherms at 273, 283 and 298 K are measured to calculate the isosteric heat of adsorption. And it is found that the total CO2 adsorptions of JLU-Liu1 are 49.6 cm3 g1 (9.7 wt%, 273 K, 760 Torr), 43.6 cm3 g1 (8.6 wt%, 283 K, 760 Torr), and 34.7 cm3 g1 (6.8 wt%, 298 K, 760 Torr) (Fig. 3a). The BET and Langmuir surface areas are estimated to be 145 m2 g1 and 221 m2 g1, respectively, which are calculated by the CO2 adsorption isotherms at 273 K. At zero-loading, JLU-Liu1 exhibits a heat of sorption (Qst) of 47.7 kJ mol1 (Fig. 3b), which is higher than those of most MOFs, similar to that of Mg-MOF-74, and smaller than that of Mmen-Cu-BTTri.2,25,26 There are only a few MOF materials that exhibit a Qst of adsorption of above 40 kJ mol1, most of them containing exposed cation or amine functionality.2 The high Qst value of JLU-Liu1 can be attributed to the small pore size effect which has been reported to increase the heat of adsorption. In the narrow-pore structures, CO2 molecules can interact with multiple pore surfaces simultaneously. This journal is
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7 Fig. 3 CO2 adsorption isotherms of JLU-Liu1 at 273 K, 283 K and 298 K (a); isosteric heat of adsorption for CO2 in JLU-Liu1 (b).
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From the CO2 and CH4 adsorption results obtained on JLU-Liu1 at 298 K, the selectivity for CO2 and CH4 was calculated to be 98 by using the initial slopes of CO2 and CH4 adsorption isotherms (Fig. S10, ESI†), which is higher than those for most MOFs.2,4,27,28 This result suggests that JLU-Liu1 is a promising candidate for separation of CO2 from CH4. In summary, a microporous MOF JLU-Liu1 with ant topology based on the 3-connected 4-PmBC ligand and unique octa-nuclear copper cluster secondary building units has been successfully constructed. Activated JLU-Liu1 exhibits higher Qst for CO2 and highly selective gas adsorption of CO2 over N2 and CH4. Further research in this area is ongoing in our group. This work was supported by the National Natural Science Foundation of China (No. 21373095, 21071059 and 21171064).
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Notes and references
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‡ Preparation of JLU-Liu-1: a mixture of 4-PmBC (0.005 g, 0.025 mmol) and CuSO45H2O (0.003 g, 0.0125 mmol) in 2 mL N,N 0 -dimethylformamide (DMF) was sealed in a 20 mL vial, then heated at 115 1C for 24 h to give green block-shaped crystals (76% yield based on CuSO45H2O). Elemental analysis: found (wt%) C, 19.8; H, 3.28; N, 5.64; S, 12.1. Calcd. (wt%) C, 20.2; H, 2.67; N, 5.3; S, 10.4. § Crystal data for JLU-Liu-1: C15.5H24.5Cu4N3.5S3O19.5, Mr = 922.23, tetragonal, space group P43212, a = b = 13.6542(9) Å, c = 42.160(4) Å, V = 7860.1(10) Å3, Z = 8, rcalc = 1.559 g cm3. A total of 49 638 reflections were collected, of which 9858 were unique (Rint = 0.0494). R1(I > 2s(I)) = 0.0349, wR2 = 0.0931. Flack parameter = 0.00(1). CCDC 947183.
20
1 (a) B. Moulton and M. J. Zaworotko, Chem. Rev., 2001, 101, 1629–1658; (b) M. O’Keeffe and O. M. Yaghi, Chem. Rev., 2012, 112, 675–702. 2 (a) P. Nugent, Y. Belmabkhout, S. D. Burd, A. J. Cairns, R. Luebke, K. Forrest, T. Pham, S. Ma, B. Space, L. Wojtas, M. Eddaoudi and M. J. Zaworotko, Nature, 2013, 495, 80–84; (b) K. Sumida,
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Chem. Commun., 2013, 49, 11433--11435
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Cite this: Chem. Commun., 2013, 49, 11433 Received 30th September 2013, Accepted 14th October 2013
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Assembly of a unique octa-nuclear copper cluster-based metal–organic framework with highly selective CO2 adsorption over N2 and CH4† Jiahuan Luo, Jing Wang, Guanghua Li, Qisheng Huo and Yunling Liu*
DOI: 10.1039/c3cc47462c www.rsc.org/chemcomm
By using 4-(pyrimidin-5-yl) benzoic acid (4-PmBC) as a ligand, a porous metal–organic framework based on unique octa-nuclear copper clusters was constructed, which exhibited highly selective CO2 uptake over N2 and CH4.
Assembly and functionalization of metal–organic frameworks (MOFs) are fascinating and significant topics in crystal engineering. Numerous MOFs have been reported not only because of their intriguing varieties of architectures and topologies,1 but also due to their potential applications in carbon dioxide capture,2 gas storage,3 separation4 and catalysis.5 Implementation of secondary building units (SBUs) as a basic and most important synthetic method, which is based on poly-nuclear metal clusters linked with numerous organic ligands, has permitted the successful assembly of MOFs.6 Plenty of MOFs have been reported mainly based on fascinating bi-nuclear, tri-nuclear, tetra-nuclear, and hexa-nuclear SBUs, such as HKUST-1 with Cu2(OH)2(CO2)4 units,7 MIL-100 and MIL-101 with Cr3O(OH)3(CO2)6 units,8 MOF-5 with Zn4O(CO2)6 units,9 and MOFs constructed from the rare Cu4Cl units,10 Yb4O units11 and Zr6O4(OH)4(CO2)12 units.12 Recently, MOFs based on a series of rare-earth metal clusters RE6(OH)8(CO2)6(CN4)6 and RE6(OH)8(CO2)12 were reported by Eddaoudi’s group.13 With the progress of human society and industry, a great amount of CO2 emissions caused by human-induced consumption are changing the climate, which has become a major and serious topic of environmental science. One of the urgent tasks to benefit today’s energy and environment is to reduce CO2 emissions. Carbon capture and storage (CCS) is one technical solution found by scientists to reduce CO2 emissions and prevent climate change.14 Thus, discovery of new materials is the core of the CCS technology. Porous materials as the newly developing materials State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China. E-mail: [email protected]; Fax: +86-431-85168624; Tel: +86-431-85168614 † Electronic supplementary information (ESI) available: Materials and methods, crystal data and structure refinement, structure information, IR spectrum, TGA, XRD, N2 isotherm, H2 isotherm and CO2:CH4 selec tivity. CCDC 947183. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/ c3cc47462c
This journal is
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The Royal Society of Chemistry 2013
have been researched by scientists for CO2 capture, such as carbon-based material,15 zeolites,16 ZIFs,17 COFs,18 PPNs,19 PAFs,20 MOFs,21 and so on. Of all porous materials, MOFs have many advantages such as abundant topological structures, designability, regulation of the structure, high specific surface area and low density, which make this type of material extremely promising for CO2 capture and separation. Herein, we report the synthesis, structure and gas adsorption properties of a novel MOF [Cu4(OH)(SO4)3(4-PmBC)(DMF)]0.5DMF 3H2O (JLU-Liu1) based on a unique octa-nuclear copper SBU, which exhibits highly selective CO2 uptake over N2 and CH4. Solvothermal reaction of CuSO45H2O and 4-PmBC in DMF at 115 1C for 24 h afforded green block-shaped crystals of JLU-Liu1;‡ single crystal X-ray diffraction analysis reveals that JLU-Liu1 crystallizes in the P43212 space group.§ There are four crystallographically independent copper atoms in the structure which exhibit four different coordination states (Fig. 1a and Fig. S1a, ESI†). Both Cu1 and Cu4 are four-connected, meanwhile Cu2 and Cu3 are fiveconnected. Cu1 is bonded with two central m4-oxygen atoms and two
Fig. 1 Single-crystal structure of JLU-Liu1 showing the 4-PmBC SBU, which can be viewed as a 3-connected node (red) and the octa-nuclear copper SBU, which can be simplified to a 6-connected node (green) (a); a schematic representation of the ant net (b); framework of JLU-Liu1 viewed along the [111] direction (c).
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Communication oxygen atoms supplied by sulfate ions while Cu4 is linked to one sulfate ion, one DMF molecule, one oxygen atom and one nitrogen atom of the 4-PmBC ligand. Cu2 is connected to four sulfate ions and one nitrogen atom of the 4-PmBC ligand, whereas Cu3 is associated with one central m4-oxygen atom, three oxygen atoms of three sulfate ions and an oxygen atom of the 4-PmBC ligand. There are six sulfate ions exhibiting three-connected coordination states (Fig. S1b, ESI†). Four copper atoms (Cu2, Cu3, Cu4 and Cu4) are connected to two oxygen atoms and two nitrogen atoms of the 4-PmBC ligand (Fig. S1c, ESI†). Around the central core of the two m4-oxygen atoms, the octanuclear copper cluster is made up of six sulfate ions and eight copper atoms. The octa-nuclear copper cluster, which is connected with six 4-PmBC ligands and two DMF molecules, can be simplified to be a 6-connected node (Fig. 1a). And the ligand 4-PmBC coordinates with three copper clusters that can be seen as a 3-connected node (Fig. 1a). Consequently, the structure of JLU-Liu1 can be described as a 3,6-connected network (Fig. 1b), which belongs to mineral-like ant topology. In the framework, there exist one-dimensional channels with dimensions 3.45 4.03 Å, after considering the van der Waals radii, running along the [111] direction (Fig. 1c). More interestingly, the distortion of the 4-PmBC ligands leads to the crystallization of JLU-Liu1 in the chiral space group P43212 which possesses four types of helices. Two opposite helices along the [001] direction intersect at the copper clusters to form a double helical chain (Fig. S2a, ESI†), and these two helical chains can be viewed as four copper clusters linked by ligands arranged in a clockwise/anticlockwise direction to generate two helices with a pitch of 42.2 Å. While other two helices along the [110] direction can be viewed as two copper clusters linked by two ligands and arranged in the clockwise–anticlockwise direction to generate a left-handed helix and a right-handed helix with a pitch of 19.31 Å (Fig. S2b, ESI†). Calculation performed using PLATON22 reveals a total solventaccessible volume equal to 3544.7 Å3 per unit cell, which accounts for 45.1% of the cell volume, offering possibilities for gas adsorption. The thermal stability of JLU-Liu1 has been measured by thermogravimetric analysis (TGA) and variable-temperature powder X-ray diffraction (VTXRD). The TGA curve (Fig. S5, ESI†) and the VTXRD patterns (Fig. S6, ESI†) indicate that JLU-Liu1 is stable up to 260 1C. The first weight loss of 17.5% from 30 to 260 1C corresponds to the loss of half a guest DMF molecule, three H2O guest molecules and one coordinated DMF molecule (calcd. 17.7%). The framework of JLU-Liu1 begins to collapse with loss of the 4-PmBC1 ligand, one central OH ions and three SO42 ions from 260 to 800 1C (found 54.6%; calcd. 54.8%). Gas adsorption studies were executed with the activated JLU-Liu1 sample to test its permanent porosity. The as-synthesized samples were immersed in methanol, acetone, dichloromethane, and acetonitrile solvents for 24 hours, respectively, to remove the high boiling point DMF and H2O guest molecules as the samples we treated before.23,24 The phase purity of the guest-exchanged samples was evaluated using X-ray powder diffraction studies (Fig. S7, ESI†). About 110 mg of dichloromethane-exchanged sample was activated at 80 1C for 10 h for the adsorption test. We executed four different gas adsorption experiments to investigate the porosity of JLU-Liu1, including N2, H2, CH4 and 11434
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Fig. 2
CO2, N2 and CH4 adsorption isotherms of JLU-Liu1 at 298 K.
CO2 gases. The resulting isotherms are shown in Fig. 2. The N2 gas sorption isotherm measured at 77 K (Fig. S8, ESI†) shows that the activated JLU-Liu1 almost cannot adsorb N2 (0.065 cm3 g1). It reveals that N2 molecules hardly enter the 1D channels of the framework; the adsorption happens on the external surface of the material. The total H2 uptake of JLU-Liu1 at 77 K is 38 cm3 g1 (Fig. S9, ESI†). The CH4 adsorption isotherm measured at 298 K reveals that the activated JLU-Liu1 scarcely adsorbs CH4 (0.5 cm3 g1). However, the activated JLU-Liu1 exhibits CO2 adsorption. The total CO2 uptake of the activated JLU-Liu1 at 298 K is 34.7 cm3 g1. This result can be attributed to the difference in the kinetic diameters of probe gases, such as CO2 (3.30 Å), N2 (3.64 Å) and CH4 (3.76 Å).2 There are 1D channels along the [111] direction in the framework of JLU-Liu1; the uncoordinated oxygen atoms of the sulfate ion are arrayed along the inner wall of the channels. The distance between two nearest opposite oxygen atoms is 3.45 Å (considering van der Waals radii of oxygen), which is smaller than the kinetic diameters of N2 and CH4. The N2 and CH4 molecules are limited from entering the channels, however the H2 (the kinetic diameter of 2.89 Å) and CO2 molecules are not restricted. The H2 uptake is pretty low compared to CO2; this result confirms that different interactions between copper and gases are one of the reasons for high CO2 selective adsorption. As mentioned above, the probable reasons for the high selective adsorption of CO2 over N2 and CH4 gases should be attributed to a cooperative effect of the size exclusion and different host–guest interactions.4 The CO2 adsorption isotherms at 273, 283 and 298 K are measured to calculate the isosteric heat of adsorption. And it is found that the total CO2 adsorptions of JLU-Liu1 are 49.6 cm3 g1 (9.7 wt%, 273 K, 760 Torr), 43.6 cm3 g1 (8.6 wt%, 283 K, 760 Torr), and 34.7 cm3 g1 (6.8 wt%, 298 K, 760 Torr) (Fig. 3a). The BET and Langmuir surface areas are estimated to be 145 m2 g1 and 221 m2 g1, respectively, which are calculated by the CO2 adsorption isotherms at 273 K. At zero-loading, JLU-Liu1 exhibits a heat of sorption (Qst) of 47.7 kJ mol1 (Fig. 3b), which is higher than those of most MOFs, similar to that of Mg-MOF-74, and smaller than that of Mmen-Cu-BTTri.2,25,26 There are only a few MOF materials that exhibit a Qst of adsorption of above 40 kJ mol1, most of them containing exposed cation or amine functionality.2 The high Qst value of JLU-Liu1 can be attributed to the small pore size effect which has been reported to increase the heat of adsorption. In the narrow-pore structures, CO2 molecules can interact with multiple pore surfaces simultaneously. This journal is
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7 Fig. 3 CO2 adsorption isotherms of JLU-Liu1 at 273 K, 283 K and 298 K (a); isosteric heat of adsorption for CO2 in JLU-Liu1 (b).
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From the CO2 and CH4 adsorption results obtained on JLU-Liu1 at 298 K, the selectivity for CO2 and CH4 was calculated to be 98 by using the initial slopes of CO2 and CH4 adsorption isotherms (Fig. S10, ESI†), which is higher than those for most MOFs.2,4,27,28 This result suggests that JLU-Liu1 is a promising candidate for separation of CO2 from CH4. In summary, a microporous MOF JLU-Liu1 with ant topology based on the 3-connected 4-PmBC ligand and unique octa-nuclear copper cluster secondary building units has been successfully constructed. Activated JLU-Liu1 exhibits higher Qst for CO2 and highly selective gas adsorption of CO2 over N2 and CH4. Further research in this area is ongoing in our group. This work was supported by the National Natural Science Foundation of China (No. 21373095, 21071059 and 21171064).
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Notes and references
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‡ Preparation of JLU-Liu-1: a mixture of 4-PmBC (0.005 g, 0.025 mmol) and CuSO45H2O (0.003 g, 0.0125 mmol) in 2 mL N,N 0 -dimethylformamide (DMF) was sealed in a 20 mL vial, then heated at 115 1C for 24 h to give green block-shaped crystals (76% yield based on CuSO45H2O). Elemental analysis: found (wt%) C, 19.8; H, 3.28; N, 5.64; S, 12.1. Calcd. (wt%) C, 20.2; H, 2.67; N, 5.3; S, 10.4. § Crystal data for JLU-Liu-1: C15.5H24.5Cu4N3.5S3O19.5, Mr = 922.23, tetragonal, space group P43212, a = b = 13.6542(9) Å, c = 42.160(4) Å, V = 7860.1(10) Å3, Z = 8, rcalc = 1.559 g cm3. A total of 49 638 reflections were collected, of which 9858 were unique (Rint = 0.0494). R1(I > 2s(I)) = 0.0349, wR2 = 0.0931. Flack parameter = 0.00(1). CCDC 947183.
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