Catalytic cycloaddition reaction of CO₂ with epoxides in the presence of the cobalt complex...

Preparing cyclic carbonates through the cycloaddition reaction of CO₂ with epoxides is an efficient technique to produce useful chemicals from CO₂, having significant applications as chemical intermediates, high-boiling solvents, and monomers of some sustainable polymers. Herein, chloromethyl polystyrene (CMPS) as support was modified via nucleophilic attack of the nitrogen of isonicotinic acid to the -CH₂Cl motif of CMPS. The resulting functionalized CMPS contains -COOH functional groups that are suitable donors for coordination with the Co²⁺ cations. Final ion exchange with Br^- led to the replacement of Cl^- ions near the positive nitrogen of the isonicotinic acid, which resulted in the preparation of the final catalyst, CMPS-INCo-Br. The catalyst was thoroughly characterized using various physicochemical techniques, supporting the successful preparation of the desired catalyst. The synthesized catalyst facilitated the cycloaddition reaction of CO₂ with epichlorohydrin, representing a full conversion (100 %) under a short reaction time (2 h), without the need for any solvent or co-catalyst. In the next studies, the catalytic activity of CMPS-INCo-Br was examined in the cycloaddition reaction of various epoxides with CO₂ under optimized conditions, depicting high conversion for epibromohydrin and full conversion for styrene oxide and 1,2-epoxy propane at more time, and acceptable results for other epoxides.