Salen-Based ionic polymers as efficient heterogeneous catalysts for CO2 cycloaddition

A Salen-functionalized ionic polymer (Zn-Salen-IP) was synthesized through a metal-assisted method. The structure and microstructure were characterized by using different characterization methods. Subsequently, the cycloaddition of CO2 with epoxide was used to investigate the catalytic activity of Zn-Salen-IP. The relationship between the types of ions within Zn-Salen-IP and its catalytic performance was thoroughly explored. Single-factor investigations were used to determine the optimal reaction conditions for catalytic CO2 cycloaddition used Zn-Salen-IP. The universality and recyclability of Zn-Salen-IP were systematically studied under the optimized conditions. Finally, Density functional theory calculations were employed to research the mechanism and pathway of the CO2 cycloaddition reaction catalyzed by Zn-Salen-IP with dual functional active sites. This provided a deep understanding for the rate-determining step and the influence of the nucleophilicity of the halogen anion in cycloaddition reaction of CO2 and epoxide.