Design of Ce-doped Zr-UiO-66 integrated with dicationic ionic liquids for highly efficient CO2 cycloaddition

Metal-organic frameworks (MOFs) possess highly tunable structures, making them promising heterogeneous catalysts for efficient CO 2 conversion reactions. In this work, cerium-modified zirconium-based metal-organic frameworks (ZrCe-UiO-66) were engineered and post-synthetically functionalized with dicationic ionic liquid moieties, enabling the simultaneous introduction of strong Lewis acidic sites and nucleophilic ionic liquid units without the need for external co-catalysts. The resulting ZrCe 0.5 -UiO-66-DIL(n-PyRIm) ( n  = 2, 3, 4; R = Et, Pr, Bu, Pe) functionalized MOFs were prepared via a modular grafting approach and exhibited remarkable catalytic performance. Among them, ZrCe 0.5 -UiO-66-DIL(2-PyBuIm) converted epichlorohydrin into the corresponding cyclic carbonate with 96% yield and 98% selectivity under solvent-free conditions at 110 °C and a CO 2 pressure of 0.1 MPa. This outstanding activity arises from a cooperative activation mechanism, in which the mixed Zr 4+ /Ce 4+ activate the epoxide substrate through Lewis acid coordination with the epoxide oxygen, thereby facilitating C O bond activation, while the bromide anions embedded in the ionic liquid moieties promote nucleophilic ring opening. In addition to high catalytic efficiency, the MOF hybrids demonstrated excellent recyclability and broad substrate tolerance. Combined CO 2 adsorption measurements and in situ infrared spectroscopy further revealed key surface intermediates, enabling a plausible mechanistic pathway for the cycloaddition process to be proposed.