Synthesis of cyclic carbonates from epoxides over bifunctional salen aluminum oligomers as a CO2-philic catalyst: Catalytic and kinetic investigation

Abstract

The solvent-free cycloaddition reaction of carbon dioxide (CO2) with epoxides has been efficiently achieved with the enhanced catalytic activity employing a series of polyether-based salen aluminum oligomers as excellent bifunctional catalysts. These CO2-philic Al(salen) derivatives could act as an easy-to-handle and homogenous catalyst and might present the enhanced recycling performance compared to the polyether-free catalysts. The promising catalysis data such as the reduced apparent activation energy suggested the synergistic effect of the metal center (Lewis acid) and the halide anion (nuclephile) had significant impact on the catalytic performance. Finally, the preliminary kinetic investigations further demonstrated that the reaction was apparent first order with respect to the concentration of epoxide and catalyst and thus followed a possible monometallic synergistic catalytic mechanism, whereas the binary catalytic system was connected with the non-first-order kinetics.