<p>CO₂ activation represents a pivotal step in the CO₂ cycloaddition reaction with propylene oxide (PO) to form propylene carbonate (PC). This study prepared a chlorine-functionalized strongly alkaline polystyrene (CPS) catalyst via copolymerization and a TEAB/SiO₂ catalyst via silane coupling for CO₂ cycloaddition reactions. The CPS catalyst achieves nearly complete PO conversion (99.8%) with high selectivity (99.6%) towards PC and maintains a PC yield &gt; 94% even after 10 reaction cycles. In contrast, the TEAB/SiO₂ exhibits rapid deactivation, with the PC yield declining from 66.8% to 5.1% after three cycles. Dynamically, the CPS catalyst exhibited a marked reduction in activation energy (20.1&#xa0;kJ·mol⁻¹) compared to TEAB/SiO₂ (32.9&#xa0;kJ·mol⁻¹), corroborating CO₂ activation through covalently anchored quaternary ammonium groups, which benefited from the higher alkalinity (2.65 mmol·g⁻¹). Moreover, the outstanding stability of the CPS catalyst arises from the robust crosslinked framework of polystyrene and divinylbenzene. This work provides a strategic approach for designing alkaline catalysts and establishes a novel pathway to develop high-performance alternatives to ionic liquids for CO₂ activation in the cycloaddition reaction between CO₂ and PO.</p> Graphical Abstract <p></p>