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

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• 作者：Yu-Chi Pan ; Hao-Yiang Wu ; Chia-Chun Kao ; Hsien-Ming Kao ; Yaw-Nan Shieh ; George T. K. Fey ; Jen-Hsuan Chang ; Hui-Hsu Gavin Tsai
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：October 22, 2009
• 年：2009
• 卷：113
• 期：42
• 页码：18251-18258
• 全文大小：375K
• 年卷期：v.113,no.42(October 22, 2009)
• ISSN：1932-7455

文摘

Ordered periodic mesoporous organosilicas containing different fractions of benzene groups in the silica framework, based on the cubic SBA-1 mesostructure (Pmn 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 that a single mesophase with various Q (from TEOS) and T silicon species (from BTEB) located randomly within the pore walls via co-condensation of BTEB and TEOS at a molecular level. Such information is often not achievable by other characterization techniques. The ¹H−²⁹Si distance information between phenylene protons and nearby T³ silicon atoms obtained from density functional theory calculations is also in good agreement with the observations of 2D ²⁹Si{¹H} HETCOR NMR experiments.