Novel Electron-Rich and Sterically Hindered Phosphonium as a Highly Efficient and Recyclable Heterogeneous Catalyst for CO2 Cycloaddition

A highly efficient heterogeneous catalyst is badly in need for producing cyclic carbonate by means of the CO2 cycloaddition. Here, a novel electron-rich and sterically hindered phosphonium heterogeneous catalyst was prepared by the functionalization of chloromethylated polystyrene particles with (2, 4, 6-trimethoxy phenyl) phosphine. Nine methoxyl groups not only endow the phosphonium with high electron density, which is demonstrated in X-ray photoelectron spectra, but also provide large steric hindrances between the anion and the cation. The unique phosphonium catalyst shows higher catalytic activities than all other reported ionic liquid based heterogeneous catalysts. It also exhibits a high selectivity and a good cycle performance. All these suggest that the phosphonium heterogeneous catalyst has the potential for practical applications in cycloadditions of CO2.