Self-catalyzed cycloaddition of CO2 and epoxides over covalent organic frameworks without adding solvent and co-catalyst

• Triazine-based covalent organic frameworks (PC-COFs) serve as efficient, solvent-free, and co-catalyst-free catalysts for CO2 cycloaddition with epoxides. • A synergistic self-catalysis mechanism is revealed, where the cyclic carbonate product enhances catalytic activity by forming Lewis acid-base pairs with the COF surface. • The optimized PC-COF-50-30 catalyst achieves 98.7% epichlorohydrin conversion and 97.6% selectivity to cyclic carbonate, with a high CO2 conversion rate of 9.0 g·g−1·h−1. • The catalyst exhibits remarkable stability and activity enhancement over multiple cycles, with a 35% increase in activity after five cycles, addressing the instability issues of metal-organic frameworks.