Polyhedral Oligomeric Silsesquioxane Based Catalyst for the Efficient Synthesis of Cyclic Carbonates

Polyhedral oligomeric silsesquioxane functionalized with imidazolium chloride peripheries (POSS-Imi) was successfully synthesized through a novel synthesis protocol. The solid was extensively characterized via¹H NMR, ¹³C NMR and IR spectroscopy as well as combustion chemical analysis, mass spectrometry and transmission electron microscopy. Moreover, an in-depth investigation through ²⁹Si NMR was performed. POSS-Imi was used for the first time as a catalyst for the conversion of CO₂ and epoxides into cyclic carbonates with excellent results in terms of both yield and selectivity. The catalyst displayed improved catalytic performance with respect to unsupported 1-butyl-3-methylimidazolium chloride. The enhanced activity was ascribed to the proximity effect generated by the increased local concentration of imidazolium species surrounding the inorganic silsesquioxane core.