Surfactant-Templated Organic Functionalized Mesoporous Silica with Phosphino Ligands

Ordered organic functionalized mesoporous silica containing covalently bonded diphenylphosphinoethyl ligands was synthesized using a surfactant-templating approach. Briefly, hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) and 2-(diphenylphosphino)ethyl triethoxysilane (PPETS) in an acidic condition produced phosphino-ligand containing organosilicate species. Subsequent co-assembly of the organosilicate species with surfactants led to the formation of ordered organic/inorganic nanocomposites. Selective surfactant removal by controlled thermal decomposition created organic functionalized mesoporous silica with diphenylphosphinoethyl ligands covalently bonded to the silica framework. Pore structures and pore sizes of the functionalized mesoporous silica were controlled by using different surfactants such as P123, F127, Brij-58, and CTAB. It was found that the added organosilane may significantly affect the mesostructure possibly through participating in the cooperative assembly process. These organic functionalized mesoporous silicas were bonded with palladium ions, resulting in the formation of catalytically active organometallic complexes that show excellent activities in both Heck and epoxides allylation reactions. Compared with the conventional homogeneous catalysts, these heterogeneous organometallic complexes can be readily separated from the reaction systems and reused without deteriorating their catalytic activities. This study provides a direct synthesis approach to efficiently synthesize a large variety of organic functionalized mesoporous silica with controlled pore sizes, pore surface chemistry, and pore structure for heterogeneous catalysts and other applications.