Vinyl-containing covalent organic frameworks co-polymerized with imidazolium ionic liquids for the efficient cycloaddition of CO2 with epoxides

The chemical fixation of CO 2 into high value-added cyclic carbonates over metal- and cocatalyst-free heterogeneous catalyst has attracted considerable attention and is still a challenge. Rationally integrating multifunctional units into porous materials has been regarded as a promising strategy to enhance catalytic efficiency. In this study, the poly (ionic liquid)-hierarchical covalent organic framework (R-PIL-COF, R refers to CH 2 NH 2 /CH 2 OH/COOH/CH 3 ) hybrids were successfully fabricated via in situ copolymerization of vinyl-containing covalent organic framework and hydrogen bond donors (HBDs)-functionalized imidazolium ionic liquids. Among, CH 2 NH 2 -PIL-COF hybrid bearing acidic and basic sites possess moderate CO 2 adsorption ability and hierarchical pore structure which promoted the activation of CO 2 and epichlorohydrin. Furthermore, the influence on the catalytic activity of various HBD groups and grafting amounts of poly (ionic liquid)s were systematically investigated, and CH 2 NH 2 -PIL–COF–45 % exhibited an exceptional catalytic performance under mild conditions (100 °C and 1 MPa CO 2 pressure). Additionally, CH 2 NH 2 -PIL–COF–45 % had broad substrate tolerance and excellent stability. Finally, a synergistic catalytic mechanism was proposed based on the experimental and characterization results. The strategy of co-polymerizing ionic liquids to COF provides a new way to develop efficient COF-based hybrids by the integration of nucleophilic units into the COF skeleton for CO 2 fixation under cocatalyst-free and mild conditions.