Linker-defect assisted catalytic fixation of CO₂ in a dual-linker metal–organic framework

We investigated the effect of linker defects induced by recycling MOF-508, a metal–organic framework with dual linkers, for the catalytic cycloaddition of the CO₂ reaction. MOF-508 catalysts are characterized using various analytical techniques such as powder XRD, FT-IR, FE-SEM, HR-TEM, TGA, BET, NH₃- and CO₂-TPD, NMR, and CO₂ adsorption isotherm. MOF-508 catalysts could perform the coupling reaction between epoxide and CO₂ with > 99% selectivity toward cyclic carbonates under solvent-free and moderate reaction conditions. After the cycloaddition reaction, the recycled MOF-508 exhibited higher catalytic activity than freshly prepared MOF-508 at all the temperature ranges. The origin of increased cyclic catalytic activities was attributed to the creating of additional catalytic active sites from the linker defects. Molecular modeling techniques were used to elucidate the catalytic mechanism and quantify the degree of linker defects in MOF-508.