Diaspore as an efficient halide-free catalyst for the conversion of CO2 into cyclic carbonates

Abstract

Efficient fixation of carbon dioxide (CO₂) into epoxides under atmospheric pressure generally necessitates the use of halide ion-containing co-catalysts. However, the use of halide ion-containing materials as catalysts is less encouraged, particularly from an industrial point of view. This demands the development of a suitable halide-free catalyst for the successful fixation of CO₂ into epoxides to prepare cyclic carbonates under atmospheric pressure. In this work, we report diaspore [α-AlO(OH)] as an efficient halide-free catalyst for CO₂ fixation. Diaspore in the presence of a small amount of dimethyl formamide is able to convert a range of epoxides into their corresponding cyclic carbonates. Hardly any loss in the catalytic activity or change in the functional/chemical characteristics of diaspore was observed after five cycles. DFT calculations reveal the spontaneity of the diaspore-catalyzed cycloaddition reaction compared to that of the diaspore-free reaction. The stabilization of the substrates and intermediates on diaspore resulted in an overall negative change in Gibb's free energy of the reaction.