Succinimide-KI: An efficient binary catalyst system for mild, solvent-free cycloaddition of CO2 to epoxides

•Succinimide(SI)-KI is a cheap and efficient catalyst system for the cycloaddition of CO2 and epoxides under mild and solvent-free condition.•The overall condition is milder than the reaction catalyzed by most of the other KI involved co-catalyst systems reported in literatures.•The activation energy for the SI-KI involved reaction was 20.3 kJ/mol lower than that of the only KI involved one due to the SI-KI synergetic effect.•A possible mechanism was proposed by kinetic studies.