Homogeneous and Heterogeneous Catalysis for the Synthesis of Cyclic and Polymeric Carbonates from CO 2 and Epoxides: A Mechanistic Overview

The utilization of CO2 for the production of useful chemicals is nowadays considered as a promising way to contribute to the reduction of greenhouse gases in the atmosphere, while valorizing at the same time this widely available resource. The synthesis of cyclic carbonates and polycarbonates via cycloaddition of CO2 to epoxides is part of the few processes already industrialized. In this field, a critical challenge is the activation of the CO2 molecule, which can be achieved by the use of effective catalysts. Catalytic systems based on metal complexes, ionic liquids or organic bases have been developed to this end. This review focuses on the different mechanisms proposed in the literature for the reaction of CO2 addition to epoxides. Better understanding of these mechanisms should allow the development of high-performance catalytic systems, able to answer industrial constraints in term of stability, separation, handling and reuse of the catalysts.