Fixation of Diluted CO ₂ into Dimethyl Carbonate by Bifunctional Base-Functionalized Poly(ionic liquid)s

Direct valorization of diluted CO2 streams remains a critical hurdle for the sustainable carbonate synthesis. Here, we report a class of bifunctional poly(ionic liquid)s that unite nucleophilic bromide anions with tunable base sites on a robust porous framework. The catalysts are readily prepared via self-condensation followed by diamine quaternization, affording high surface areas and exceptional thermal stability. Under 1 MPa CO2 and 140 °C, the optimized PDBX-TMHDA catalyst realized one-step synthesis of dimethyl carbonate in >68% yield. Notably, it maintains 65% yield when challenged with 15% CO2 in N2, mimicking flue gas. The catalyst retains a constant activity over five cycles and is easily recovered by centrifugation. This work establishes a scalable, one-step route for converting low-grade CO2 into high-value carbonates and provides insights into integrating capture and catalysis within multifunctional solid materials.