Phenanthroimidazolium-Based Hypercrosslinked Polymers for Catalytic CO₂ Conversion to Cyclic Carbonates

In this work, two phenanthroimidazolium-based ionic hypercrosslinked polymers, PIB-iHCP and PIBB-iHCP, have been successfully synthesized via AlCl₃-catalyzed Friedel-Crafts alkylation and fully characterized. Owing to the rigid structure of the building blocks, the resultant PIB-iHCP and PIBB-iHCP demonstrated relatively high specific surface areas of 612 and 568 m² g^-1, respectively. The presence of imidazolium rings endows hypercrosslinked networks with not only high CO₂ uptake capacity (3.07 mmol g^-1 for PIB-iHCP and 3.37 mmol g^-1 for PIBB-iHCP at 273 K and 1000 mbar), but also high catalytic activity toward the cycloaddition of CO₂ to epoxides. For example, PIBB-iHCP was found to be effective for converting epibromohydrin to the corresponding cyclic carbonate under mild conditions (60°C, 0.1 MPa), with a quantitative conversion (99%) and selectivity (99%). Owing to its high catalytic versatility and recyclability, PIBB-iHCP emerges as a promising heterogeneous catalyst for the cycloaddition of CO₂ to epoxides.