Ionic Polymers with Phenolic Hydroxyl Groups as Hydrogen Bond Donors Toward Enhanced Catalytic Performance for CO2 Conversion

In this study, imidazolium-based multifunctional ionic polymer (IP 1-IP 3) series, co-incorporated with phenolic hydroxyl groups as hydrogen bond donors (HBDs) and Cl- as nucleophiles, are synthesized by a facile quaternization method. The physicochemical characterizations of these IPs are systematically examined by using FTIR, XPS, BET, TGA, CO2-TPD, SEM with elemental mapping and TEM methods. Their catalytic activities are evaluated toward the conversion of carbon dioxide (CO2) and epoxides into cyclic carbonates under solvent- and additive-free environments. Apart from the synergy effect between HBDs and Cl-, it is found that the types of the spacer linking the two imidazole units in the diimidazole precursors (L-1-L-3) also play an important role in the catalytic activity. And IP 2, with a pyridine spacer as a Lewis base site, exhibits the best catalytic performance under solvent-free mild conditions i. e., atmospheric pressure CO2, 80 degrees C, and 5 h. Notably, the catalyst demonstrates a good substrate applicability. Furthermore, IP 2 exhibited good reusability, stability, and it can be recycled for ten successive runs with stable and potential catalytic activity. This study provides an alternative route to construct IPs with efficient activity for CO2 catalytic conversion and fixation under mild-conditions.