Dicationic ionic liquid-grafted UiO-66 as efficient catalyst for CO2 conversion into cyclocarbonate under cocatalyst-free and solventless conditions

CO 2 chemical fixation offers a feasible approach for carbon mitigation and high-value utilization, but it is still challenging to develop an efficient catalyst for CO 2 conversion into cyclic carbonate. Herein, the triethylenediamine-derived dicationic ionic liquids (DIL-X, X = Cl, Br, and I) were grafted into UiO-66 linkers through self-assembly of Zr 4+ ions and the mixed ligands of terephthalic acid and DIL-bearing dicarboxylic acid, resulting in UiO-66-DIL-X n , ( n designated as molar amount of the feeding DIL-X). Their catalytic performance was evaluated by the epoxide cycloaddition reaction in the absence of solvent and cocatalyst. Among them, the UiO-66-DIL-Cl 0.4 catalyst exhibited outstanding performance, with a chloropropene carbonate yield of 92% and a high selectivity of 99% under 0.1 MPa CO 2 at 110 °C for 16 h. Its high activity could be ascribed to the cooperativity among Lewis acidity of MOF nodes, the enhanced CO 2 absorption, and the strong nucleophilicity offered by halogen ions of ionic liquid-modified MOF. Moreover, UiO-66-DIL-Cl 0.4 presented excellent recyclability and substrate extension. A potential catalytic mechanism for the epoxide-CO 2 cycloaddition into cyclic carbonate has been proposed. This work will shed light on the rational design of functionalized MOFs-based catalysts for CO₂ utilization.