Functional Poly(Ionic Liquid)s: Catalytic Conversion of CO2

This study reports the synthesis and catalytic evaluation of a series of imidazolium-based polymeric ionic liquids (PILs) for the cycloaddition of CO2 to epichlorohydrin (ECH). The synthesized catalysts include homopolymers, poly(3-hydroxyethyl-1-vinylimidazole chloride) (pHVImCl) and poly(3-carboxymethyl-1-vinylimidazole chloride) (pCMVImCl), and their block copolymers with polystyrene, synthesized for the first time, pS-b-pHVImCl and pS-b-pCMVImCl. Structural characterization by NMR, IR spectroscopy, and gel permeation chromatography confirmed the successful synthesis. The block copolymers exhibited a low polydispersity index (PDI 1.1–1.2), which is indicative of homogeneous chain lengths and the propensity to form ordered nanostructures, whereas the homopolymers showed higher PDI (2.4–2.9). Catalytic testing at 90 °C and 1 MPa CO2 for 4 h revealed a clear activity trend: pCMVImCl < pHVImCl < pS-b-pCMVImCl < pS-b-pHVImCl, with conversions exceeding 75% for all catalysts and a maximum of 82.69% for pS-b-pHVImCl. These results demonstrate that the catalytic performance of PILs is governed by a synergistic interplay between the local chemical functionality of the ionic moiety and the overall polymer architecture. Based on these results, the synthesized polymeric ionic liquids, particularly pS-b-pHVImCl, demonstrate strong potential for creating multifunctional materials. Their ability to self-assemble into ordered nanostructures with distinct hydrophobic and hydrophilic domains provides a foundational architecture for combined gas separation and catalysis. The observed “micellar catalytic effect”, which enhances local reagent concentration near active sites, could be leveraged in a membrane reactor to simultaneously capture and convert CO2 directly within the membrane. This integrated “separation–reaction” approach represents a promising strategy for advancing circular carbon economy technologies.