A Zn(II) metal-organic framework constructed by a mixed-ligand strategy for CO2 capture and gas separation

By introducing the 1,2,4-triazole ligand to the tetracarboxylate system, an anionic metal-organic framework [(CH3)2NH2][Zn2(ABTC)(Tz)]·3DMF (compound 1, ABTC = 2,2’,5,5’-azobenzene tetracarboxylic acid, Tz = 1,2,4-triazole and DMF = N,N-dimethylformamide), has been synthesized under solvothermal conditions. There are two types of inorganic secondary building units (SBUs) in compound 1, a classical Zn-paddlewheel [Zn2(COO)4] and a metal cluster of [Zn2(Tz)2(COO)4], which are linked by ABTC4- to form a 3D porous framework. The two inorganic SBUs as 6-connected nodes and ABTC4- as 4-connected nodes, compound 1 can be simplified to a new (4, 6, 6)-connected topology with a point symbol of (32.62.72) (34.42.64.75). Compound 1 displays CO2 adsorption capacity of 92.1 cm3 g-1 at 273 K under 1 atm. Furthermore, 1 exhibits good adsorption capacity for small molecular gases (CH4, C2H6 and C3H8) and separation selectivity for CO2/CH4, C2H6/CH4 and C3H8/CH4.