Two porous metal-organic frameworks (MOFs) based on mixed ligands: synthesis, structure and selective gas adsorption

摘要

Two new three-dimensional (3D) porous structures based on the mixed flexible and rigid organic ligands, [Cd_(1.5)(bmip)(tpa)_(1.5)(DMF)_(1.5)]_n (1) and [Co_(1.5)(bmip)_(0.5)(bpdc)_(1.5)(DMF)2]_n (2) (bmip = 1,3-bis(2-methylimidazolyl)propane, H2tpa = terephthalic acid, H2bpdc = biphenyl-4,4′-dicarboxylic acid, DMF = N,N-dimethylformamide) have been prepared under solvothermal conditions. Complex 1 contains a trinuclear Cd unit, in which the trinuclear Cd cluster acts as an eight-connected node with two pairs of flexible bmip and six rigid tpa ligands. Complex 2 exhibits a two-fold interpenetrated porous network based on a trinuclear Co cluster as eight-connected vertices with two flexible bmip and six rigid tpa ligands. Both 1 and 2 show selective gas adsorption of CO2 over N2 and H2. Furthermore, complex 1 displays an uncommon CO2 adsorption isotherm and hysteretic desorption behaviors at 195 K.