High-efficiency acid-base catalysts: ZrO2, TiO2, amine, and Br functionalized porous polymers for CO2 and epoxide to cyclic carbonate conversion

The development of new materials capable of converting carbon dioxide (CO2) into value-added products has emerged as a crucial strategy in addressing global climate change and promoting sustainable industrial practices. As CO2 emissions continue to rise, innovative catalytic systems that facilitate its utilization as a C1 carbon source are gaining significant attention. Such advancements not only contribute to carbon capture and utilization (CCU) efforts but also support the transition toward greener chemical processes by reducing dependence on fossil-derived feedstocks. The design of high-performance heterogeneous catalysts with synergistic acid-base sites is particularly important for improving catalytic efficiency in CO2 conversion. In this study, bifunctional catalysts were synthesized by embedding ZrO2 and TiO2 (ZT) nanoparticles into a polyamide-imide polymer dope, followed by phase inversion using a "dry-jet, wet-quench spinning" process to form porous hollow fibers (PF). The fibers were then post-grafted with 3-aminopropyltrimethoxysilane (APF) to introduce amine functional groups and further modified with 1,2-dibromopropane at 110 degrees C to immobilize covalent hydrogen-bond donor groups (-OH and -NH) and nucleophilic (Br-) species. These heterogeneous bifunctional catalysts were then evaluated for the synthesis of cyclic carbonates from CO2 and epoxides. The catalytic performance was systematically investigated under various reaction conditions, including temperature, reaction time, solvent selection, and CO2 pressure. The optimized catalyst system achieved 100% styrene oxide (SO) conversion and >99% selectivity for styrene carbonate (SC) via the cycloaddition reaction using the Br@ZT-APF catalyst in the presence of solvents. Beyond achieving high conversion rates, the catalyst demonstrated excellent recovery, thermal stability, and recyclability for at least five consecutive cycles without significant loss of activity.