Conversion of CO2 to cyclic carbonates using metal- and halogen-free Lewis pairs

Abstract

The development of efficient and environmentally-friendly catalysts for the catalytic conversion of carbon dioxide (CO₂) has been extensively investigated over a prolonged period. In this work, we successfully performed a cycloaddition reaction between CO₂ and epoxides using metal- and halogen-free Lewis pairs as catalysts. Mechanistic investigations have revealed that Lewis acid-base pairs (LPs), a combination of Lewis acids (LAs) and Lewis bases (LBs), act in concert to activate epoxide and CO₂, resulting in the efficient synthesis of various cyclic carbonates with high yields. Various epoxides are converted into cyclic carbonates with yields as high as 99% under cocatalyst-free and solvent-free conditions. Moreover, this homogeneous Lewis pair was incorporated into hypercrosslinked polymers through the Friedel-Crafts reaction, enabling the convenient recovery and reuse of the catalysts.