Two-dimensional metal-organic frameworks for selective separation of CO2/CH4 and CO2/N2

Two two-dimensional (2D) microporous metal-organic frameworks, [Zn-2(TMTA)(DMF)(2)].NO(3.)2H(2)O.3DMF (1, DMF = N, N-dimethylformamide) and [Zn-3(TETA)(2)(DMF)(4)].3DMF (2), were synthesized via a solvothermal reaction, where H(3)TMTA and H(3)TETA are 4,4 ',4 ''-(2,4,6-trimethylbenzene-1,3,5-triyl) tribenzoic acid and 4,4 ',4 ''-(2,4,6-triethylbenzene-1,3,5-triyl) tribenzoic acid, respectively. Crystallographic studies, including powder and single crystal X-ray diffraction (XRD) analyses, reveal that compound 1 features a 2D microporous framework composed of paddle-wheel Zn-2(RCOO)(3) clusters and TMTA(3-) ligands, while the 2D double-layered structure 2 is assembled by discrete trinuclear Zn-3(RCOO)(6) clusters and TETA(3-) ligands. Both activated frameworks of 1 and 2 show permanent porosities with Brunauer-Emmett-Teller (BET) surface areas of 788 and 421 m(2) g(-1), respectively. Desolvated 1 exhibits a considerable carbon dioxide adsorption of 94.2 cm(3) g(-1) at 1 bar and 273 K, which is higher than that of 42.0 cm(3) g(-1) for 2. Furthermore, both materials show selective carbon dioxide adsorption over methane and nitrogen at ambient temperature.