Magnetically recyclable Fe3O4@SiO2 supported phosphonium ionic liquids for efficient and sustainable transformation of CO2 into oxazolidinones

Carbon dioxide (CO2) as a C1 building block to synthesize 2-oxazolidinones is an environmental and sustainable approach. In this work, we present the synthesis and characterization of novel heterogeneous catalysts by immobilizing homogeneous phosphonium ionic liquids (ILs) onto magnetic Fe3O4@SiO2, which could realize the cycloaddition of CO2 and a range of aziridines into 2-oxazolidinones under mild conditions of 90 degrees C and 1 atm CO2 pressure. The immobilized IL Fe3O4@SiO2@PILCeCl4 demonstrated remarkable catalytic activity in the CO2 transformation, leading to high to excellent yields (87-95%) as well as excellent selectivities (98-99.2%) in the absence of solvent at reaction times of 8-10 h, from alkyl- or aryl-substituted and N-alkyl-substituted aziridines. The heterogeneous and magnetic nature of the catalyst facilitated effortless recovery and efficient reusability, which could be easily separated and reused up to five consecutive cycles without considerable decrease in catalytic activity. This protocol provides a novel and efficient strategy for producing 2-oxazolidinones, with potential applications in chemical transformation of CO2 into value-added chemicals.