Significant Gas Adsorption and Catalytic Performance by a Robust Cu(II) -MOF Derived through Single-Crystal to Single-Crystal Transmetalation of a Thermally Less-Stable Zn(II) -MOF.

By using a bent tetracarboxylic acid ligand that incorporates a pendent-NH2 functional group, a 3D Zn(II)-framework (1) based on Zn2 (CO2)4 secondary building units and Zn12 (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 1Cu. Unlike 1, the Cu(II) analogue is very stable and can be activated by removing metal-bound lattice solvent molecules by heating to afford 1Cu'. The activated 1Cu' exhibits excellent H2 storage (2.29 wt%) at 77 K and a high 32.1 wt% CO2 uptake at 273 K. Additionally, it displays significant selectivity for CO2 adsorption over N2 and H2 and can catalyse size-selective Knoevenagel condensation reactions.