Novel and reusable magnetic MOF nanocomposite coupled ionic liquid-promoted efficient chemical fixation of CO2 into α-alkylidene cyclic carbonates

Carbon dioxide as a C1 building block to synthesize α-alkylidene cyclic carbonates is an environmental and sustainable approach. In this work, we designed and synthesized a type of multifunctional magnetic MOF nanocomposite catalysts, which could realize the carboxylic cyclization of CO₂ and propargylic alcohols into α-alkylidene cyclic carbonates under solvent-free conditions. Among all the prepared nanocomposites, the MnFe₂O₄@SiO₂@Cu-MOF nanocomposite is the best in catalytic activity combined with the tetrabutylphosphonium acetate ([Bu₄P]OAc) ionic liquid cocatalyst. The catalytic system MnFe₂O₄@SiO₂@Cu-MOF/[Bu₄P]OAc displayed excellent performance in catalyzing the carboxylic cyclization of CO₂ and different propargylic alcohols, and a series of α-alkylidene cyclic carbonates were obtained in high to excellent yields (88 ∼ 98 %) under mild reaction conditions (0.2 MPa, 35 °C). In addition, the two-component catalytic system had high stability and reusability, and can be easily separated and reused up to six consecutive cycles without considerable decrease in catalytic activity. Moreover, using the ionic liquid [Bu₄P]OAc as the cocatalyst, the nanocomposite had good substrate adaptability for the catalytic carboxylic cyclization, which opens interesting prospects for the development of new magnetic MOF nanocomposites as efficient heterogeneous catalysts for the chemical transformation of CO₂ into value-added chemicals.