Benzyl substituted imidazolium ionic liquids as efficient solvent-free catalysts for the cycloaddition of CO2with epoxides: Experimental and Theoretic study

•Eight benzyl substituted imidazolium ionic liquids are firstly synthesized.•They are efficient homogeneous catalysts for cycloaddition of CO2with PO.•The reaction condition is benign with high product yield.•No solvent and co-catalyst are required.•The reaction mechanism is elucidated by DFT calculation.