Lewis Acid Catalysis of TiO4 Tetrahedra on Mesoporous Silica in Water
Lewis Acid Catalysis of TiO4 Tetrahedra on Mesoporous Silica in Water
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DOI：
10.1021/cs401149n
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发表时间：
2014-03
期刊：
影响因子：
12.9
通讯作者：
H. Shintaku;K. Nakajima;M. Kitano;N. Ichikuni;M. Hara
中科院分区：
文献类型：
--
作者：
H. Shintaku;K. Nakajima;M. Kitano;N. Ichikuni;M. Hara
研究了TiO 4沉积介孔二氧化硅（TDMS）作为耐水固体刘易斯酸催化剂的性能。通过使用Ti（i-pro）4的简单后接枝技术制备的TDMS具有大的BET表面积（约1000 m2）。450 m2 g-1）和有序的介孔结构。紫外-可见漫反射光谱（UV-vis DRS），X射线吸收近边结构（XANES），和CO吸附测量与傅里叶变换红外（FTIR）光谱表明，孤立的TiO 4四面体TDMS具有刘易斯酸性，即使在水的存在下。TDMS上的刘易斯酸中心对苯甲醛到乳酸的氢化物转移以及苯甲醛与1-三甲基甲硅氧基-环己烯在水中的Mukaiyama-aldol缩合反应表现出比常规的多相和均相刘易斯酸更高的催化性能，包括三氟甲磺酸钪（III）（Sc（OTf）3），其甚至在水中也起作用。TDMS的高催化性能可归因于在水中孤立的TiO 4四面体的刘易斯酸催化。
TiO4-deposited mesoporous silica (TDMS) was studied as a water-tolerant solid Lewis acid catalyst. TDMS prepared by a simple postgrafting technique using Ti(i-pro)4 has a large BET surface area (ca. 450 m2 g–1) and ordered mesoporous structure. Ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray absorption near edge structure (XANES), and CO adsorption measurements with Fourier transform infrared (FTIR) spectroscopy revealed that isolated TiO4 tetrahedra on TDMS have Lewis acidity, even in the presence of water. Lewis acid centers on TDMS exhibit higher catalytic performance for the hydride transfer of pyruvaldehyde to lactic acid and the Mukaiyama-aldol condensation of benzaldehyde with 1-trimethylsilyloxy-cyclohexene in water than that of conventional heterogeneous and homogeneous Lewis acids, including scandium(III) triflate (Sc(OTf)3), which also works even in water. The high catalytic performance of TDMS can be attributed to Lewis acid catalysis of isolated TiO4 tetrahedra in water.