Enhanced cycloaddition of CO2 to epichlorohydrin over zeolitic imidazolate frameworks with mixed linkers under solventless and co-catalyst-free condition

An efficient dual-ligand zeolitic imidazolate framework ZIF-8-90 was fabricated for the synthesis of five-membered cyclic carbonate from CO2 and epichlorohydrin (ECH) in the absence of co-catalysts and solvents. The effects of various reaction parameters were studied. The dual-ligand ZIF-8-90 showed very high selectivity (up to 99%). ZIF-8-90 exhibited better catalytic ability with lower cost than ZIF-90 and enhanced framework stability with significantly improved selectivity compared to ZIF-8. Moreover, the catalyst has been successfully reused for three cycles with negligible decrease in the catalytic activity. A plausible mechanism for the ZIF-8-90 catalyzed ECH - CO2 cycloaddition under solvent-free and co-catalyst-free has been proposed.