A room temperature synthesizable and environmental friendly heterogeneous ZIF-67 catalyst for the solvent less and co-catalyst free synthesis of cyclic carbonates

Catalysts capable of materializing high performance without compromising the green credentials are a pre-requisite for the establishment of a sustainable process. Herein, ZIF-67, a cobalt based zeolitic imidazolate framework possessing acid-base bifunctionalities, is reported for its application in the artificial fixation of CO2 via cyclic carbonate synthesis. The ZIF-67 is synthesizable in water at room temperature with inexpensive precursors in less than 3 h. The heterogeneous ZIF-67 was found catalytically efficient towards CO2-oxirane coupling under moderate reaction conditions with nearly complete selectivity towards five membered cyclic carbonates under solvent free and co-catalyst free conditions and it exhibited good reusability, outperforming the previously reported ZIF catalyst systems on efficiency and economic-environmental aspects. Crystal defects on the surface of the catalyst supposedly assumed to exert opportunistic catalytic roles in this liquid phase cycloaddition reaction and the plausible mechanism with multiple physico-chemical characterizations was proposed. In comparison with the previously reported heterogeneous catalysts synthesized by complicated multistep synthesis involving organic solvents and high temperature, the facile one-pot water mediated room temperature synthesis of ZIF-67 with acido-basic dual active sites makes it more practical for high-performance heterogeneous catalysis ensuring green chemistry perspectives.