Disilazane functionalization of large-pore hybrid periodic mesoporous organosilicas

Ordered inorganic–organic hybrid periodic mesoporous organosilicas (HPMOs) with hexagonal symmetry were synthesized under acidic conditions by using triblock copolymer Pluronic P123 as a structure-directing agent and mixtures of tetraethylorthosilicate (TEOS) and bis(triethoxysilyl)ethane (BTEE) as the silica source. All mesoporous materials were characterized by powder X-ray diffraction, N2 physisorption, and 13C CP MAS NMR and 29Si MAS NMR spectroscopy. High TEOS : BTEE molar ratios improved the long-range ordering of the HPMOs remarkably, and increased the pore diameter, while the pore wall thickness gradually decreased. Addition of the organic expander molecule mesitylene to the synthesis gel also enlarged the pore diameter and improved the long-range ordering of the materials. Surface silylation with the bissilylamine reagents tetramethyldisilazane (HN(SiHMe2)2), hexamethyldisilazane (HN(SiMe3)2) and diphenyltetramethyldisilazane (HN(SiMe2Ph)2) revealed that the silylation efficiency decreased according to the steric bulk of the silyl groups affording surface silanol populations in the range 0.76–2.19 OH nm−2.