Synergistic effect of alkali halide and Lewis base on the catalytic synthesis of cyclic carbonate from CO2 and epoxide

► Alkali metal halide catalyzed cyclic carbonate synthesis using epoxide and CO2. ► Convenient and solventless reaction achieved at 130 °C and 2 MPa of CO2 pressure. ► Excellent synergic effect between alkali metal halide and Lewis base on the catalytic reactions. ► Absence of Lewis base makes the reaction ∼40 times less efficient. ► Spectroscopic investigation leading to elucidation of possible reaction pathway.