Significant Gas Adsorption and Catalytic Performance by a Robust CuII-MOF Derived through Single-Crystal to Single-Crystal Transmetalation of a Thermally Less-Stable ZnII-MOF

By using a bent tetracarboxylic acid ligand that incorporates a pendent -NH2 functional group, a 3D Zn-II-framework (1) based on Zn-2(CO2)(4) secondary building units and Zn-12(CO2)(24) supramolecular building blocks has been synthesized. Framework 1 is thermally less stable, which precludes its application as a porous framework for gas adsorption or catalytic studies. This framework undergoes single-crystal to single-crystal transmetalation to give isostructural 1(Cu center dot) Unlike 1, the Cu-II analogue is very stable and can be activated by removing metal-bound lattice solvent molecules by heating to afford 1(Cu)'. The activated 1(Cu)' exhibits excellent H-2 storage (2.29 wt%) at 77K and a high 32.1 wt% CO2 uptake at 273 K. Additionally, it displays significant selectivity for CO2 adsorption over N-2 and H-2 and can catalyse size-selective Knoevenagel condensation reactions.