Flexible Metal-Organic Frameworks for Light-Switchable CO2 Sorption Using an Auxiliary Ligand Strategy.

We report the synthesis and characterization of two photoactive metal-organic frameworks (MOFs), TCM-14 and TCM-15. The compounds were synthesized by incorporating 4,4'-azopyridine auxiliary ligands into pto-type scaffolds that are composed of dinuclear copper(II) "paddle-wheel"-based secondary building units and flexible, acetylene-extended, tritopic benzoate linkers. Room temperature CO2 sorption of the MOFs was studied, and UV-light irradiation is shown to result in reduced CO2 adsorption under static conditions. TCM-15 reveals a dynamic response leading to an instant desorption of up to 20% of CO2 upon incidence of UV light because of the occurrence of nonperiodic structural changes. Physicochemical and computational density functional theory studies were carried out to gain insight into the mechanism of the interaction of light with the frameworks.