A green catalysis of CO₂fixation to aliphatic cyclic carbonates by a new ionic liquid system

A mixed ionic liquid system has been developed for the efficient catalysis of CO2addition to aliphatic epoxides without involving any transition metal catalysts or other additives. The ionic liquid integrated with pyridinium and pyrrolidinium groups (1·(Br)3) together with a non-polar ionic liquid (3·(Ntf)2) effectively transformed non-polar aliphatic epoxides to cyclic carbonates by the reaction with CO2under mild CO2pressure (3.0 MPa) and reaction temperature (80 C). The presence of 3·(Ntf)2remarkably improved the catalytic activity of 1·(Br)3towards non-polar epoxides by increasing the miscibility of catalyst with the substrates. The mixed ionic liquid system is robust enough to be recycled without any significant loss of catalytic activity. GC-MS studies were performed to reveal the reaction pathways to the cyclic carbonates and a feasible model accounting for the effective CO2activation in the ionic liquid system was proposed using density functional theory (DFT) calculations.