Dual hydrogen bond donor functionalized hierarchical porous poly(ionic liquid)s for efficient CO2 fixation into cyclic carbonates

Abstract

CO2 capture and conversion to high-value-added products is critical for the purposes of environmental preservation and carbon resource utilization. In this study, a novel class of porous poly(ionic liquid)s has been synthesized, incorporating dual hydrogen bond donors (amide and hydroxyl groups) and nucleophiles (Br-) as multiple effective active sites for the cycloaddition reaction between CO2 and epoxides. The presence of dual hydrogen bond donors not only provides two active sites for synergistic catalysis with epoxides but also enhances the capacity for CO2 adsorption. Comprehensive characterization has been conducted to elucidate the structural features and properties of these innovative materials. By regulating the ratio between ionic liquid monomer and divinylbenzene, a hierarchical porous structure favorable for the reaction was constructed, resulting in optimized catalytic activity comparable to that of bulk ionic liquid monomers. Furthermore, this catalyst exhibits remarkable structural stability with minimal activity loss even after five consecutive use cycles. Combining density functional theory calculations with in-situ Fourier transform infrared spectroscopy analysis, the catalytic mechanism was proposed that the dual hydrogen bond donors and Br- synergistically promote ring-opening reactions of epoxides, while amide groups serve as basic sites to enhance CO2 adsorption during the reaction process.