A NbO-type copper metal-organic framework decorated with carboxylate groups exhibiting highly selective CO2 adsorption and separation of organic dyes

A porous Cu metal-organic framework (1) based on a pentacarboxylate ligand and paddlewheel SBU was synthesized and structurally characterized. Complex 1 possesses a NbO-type framework with uncoordinated -COO- groups, resulting in its good selectivity for CO2/N-2 (36) and CO2/CH4 (12) as well as a large CO2-uptake capacity of 140 cm(3) g(-1) at 273 K and 1 bar. Grand Canonical Monte Carlo (GCMC) simulations revealed that strong CO2 adsorption sites exist near the open Cu-II sites and the uncoordinated -COO- groups. Significantly, complex 1 exhibits water resistance and selective adsorption of cationic methylene blue (MB+) in aqueous solution and the adsorbed MB+ can be released in saturated NaCl solution, making it also a promising porous material for charge and pore-size dependent large-molecule capture and separation. The existence of coordinatively unsaturated metal sites as well as the exposed -COO- groups in the framework of 1 is responsible for its selective gas adsorption and dye separation.