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

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.