Silica-Grafted Basic Amino Acids as Environmentally Benign Catalysts for the Solventless Synthesis of Cyclic Carbonates from Epoxides and CO2 under Metal-Free and Halide-Free Conditions

A series of basic amino acids immobilized onto solid supports that can play cooperative roles was developed and applied as environmentally benign catalytic systems for the solventless synthesis of cyclic carbonates from epoxides and carbon dioxide under metal-free and halide-free conditions. The highest yield of styrene carbonate was achieved with silica supported l-histidine, associated with the acidic nature of silica: Si-OH groups on the silica surface act as a weak acid to activate the epoxide for the synergetic effect with the basic amino acid. The influence of various reaction parameters on catalytic activity was investigated. Moreover, the catalyst exhibited good recyclability.