Zn(<sc>ii</sc>) and imidazolium salt ionic liquids bifunctionalized catalysts as efficient heterogeneous catalysts for CO2 cycloaddition: preparation, mechanism and stability

Bifunctional catalysts (Zn/BMMs-ILs) were synthesized via co-condensation involving zinc, followed by post-grafting with imidazolium salt ionic liquids (ILs). Furthermore, the content of Zn in the bifunctional catalysts can be tuned by changing the molar ratio of Zn to Si during the synthesis process of Zn functionalized BMMs. 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/BMMs-ILs. Moreover, kinetics studies and density functional theory (DFT) calculations were conducted along the single and dual functional catalyst pathways to gain a deep understanding of the enhanced catalytic activity of the bifunctional catalysts in the CO2 cycloaddition reaction. Finally, by comparing Zn/BMMs-ILs with our previously reported BMMs-ILs, the recycle stability and deactivation mechanisms of the catalysts were investigated. It has been proven that the hybrid of Zn in the bifunctional catalysts not only enhances catalytic activity but also significantly contributes to the improved stability.