Model System for Solid-State NMR Study on Co-condensation Behavior of Silicon Precursors in Periodic Mesoporous Organosilicas

Ordered periodic mesoporous organosilicas containing different fractions of benzene groups in the silica framework, based on the cubic SBA-1 mesostructure (Pm3n mesophase), were synthesized with the direct-synthesis route via co-condensation of tetraethoxysilane (TEOS) and 1,4-bis(triethoxysilyl)benzene (BTEB) under acidic conditions using cetyltriethylammonium bromide as a structure-directing agent. A significantly large amount of TEOS, up to 70 mol % based on silica, can be incorporated into the silica wall without degrading the structural integrity of the materials. By optimization of the synthesis compositions, the resulting materials exhibited much higher surface areas (up to 1210 m2/g) and larger pore volumes (up to 0.64 cm3/g) as compared to the previous analogue, which only exhibited a surface area of 381 m2/g and a pore volume of 0.11 cm3/g. Two-dimensional (2D) 29Si{1H} heteronuclear correlation (HETCOR) NMR spectra, acquired as a function of contact time, provided direct spectroscopic evidence...