Direct Synthesis and Solid-State NMR Characterization of Cubic Mesoporous Silica SBA-1 Functionalized with Phenyl Groups

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• 作者：Hsien-Ming Kao ; Chia-Hsiu Liao ; Tzu-Ti Hung ; Yu-Chi Pan ; Anthony S. T. Chiang
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：March 25, 2008
• 年：2008
• 卷：20
• 期：6
• 页码：2412 - 2422
• 全文大小：681K
• 年卷期：v.20,no.6(March 25, 2008)
• ISSN：1520-5002

文摘

Well-ordered mesoporous silicas SBA-1 (cubic Pm3n symmetry) functionalized with phenyl groups have been synthesized via co-condensation of tetraethoxysilane (TEOS) and phenyltriethoxysilane (PhTES) under acidic conditions. The synthesis parameters such as temperature, type of surfactant, and synthesis composition have been systematically investigated as a function of PhTES contents. The phenyl-containing units are incorporated quantitatively and reach a maximum PhTES loading up to 33 mol % (based on silicon) without a significant degradation of the structural ordering of the Pm3n mesophase. A combination of multinuclear (¹H, ¹³C, ²⁹Si) solid-state NMR and two-dimensional (2D) solid-state NMR correlation techniques such as ¹³C{¹H} and ²⁹Si{¹H} HETCOR (heteronuclear correlation) and ¹H-¹H exchange NMR has been used to establish framework locations of phenyl functional groups that are incorporated in the mesoporous structure and their interactions with the surfactant molecules. 2D ¹³C{¹H} HETCOR NMR experiments reveal that the phenyl moieties are in close spatial proximity to the trimethylammonium headgroups of the cationic surfactant species in the as-synthesized materials, suggesting that there are some specific interactions between them to maintain the surfactant packing parameter (g) smaller than 1/3 necessary for the formation of the cubic mesophase. The detection of couplings between the protons associated with various ²⁹Si species via ²⁹Si{¹H} HETCOR NMR established that the T silicon species due to the phenyl groups incorporated are in closer proximity to the Q⁴ silicon species than to the Q³ silicon species. This observation also provides direct molecular-level evidence for the co-condensation of PhTES and TEOS in the synthesis of mesoporous organosilicas.