New amine-functionalized cobalt cluster-based frameworks with open metal sites and suitable pore sizes: multipoint interactions enhanced CO2 sorption.

By employing the mixed-linker synthetic strategy, two new cobalt(II) cluster-based frameworks, [Co(2.5)(btc)(atz)2(Hatz)(DMF)]·2DMF (1) and [Co(2.5)(btc)(Hbtc)0.5(atz)(CH3CN)(H2O)]·H2O (2), constructed from the same initial materials Co(NO3)2, 1,3,5-benzenetricarboxylic acid (H3btc) and 3-amino-1,2,4-triazole (Hatz), have been synthesized by solvothermal reactions. Crystal-structure analyses demonstrated that 1 and 2 are three-dimensional (3D) porous frameworks based on Co-triazolate chain/layer and tricarboxylate pillars. Thermogravimetric analysis (TGA) and power X-ray diffraction (PXRD) measurements showed that both of them have high thermal stability and good water stability. Remarkably, both the structures of desolvated 1 and 2 contain suitable pore sizes and highly polar channel systems functionalized by amino groups, open metal sites, carbonyl or free carboxylic acid sites and uncoordinated triazolate nitrogen atoms on the pore surfaces, exhibiting multipoint interactions between CO2 molecules and frameworks, resulting in high CO2 uptake and selectivity for CO2 over N2.