Synthesis and Development of Nano-structured Organic-Inorganic Cooperative Catalysts

在这项研究中，我们研究了原型催化体系，以证明“有机-无机协同催化体系”概念的优势。一种是负载在介孔氧化铝上的Pd，其具有有机改性以控制α-β不饱和醛氢化的选择性。另一种体系是包含杂多酸无机分子和疏水性中孔二氧化硅的高活性固体酸催化剂。在前者中，各种有机分子被接枝到介孔氧化铝的孔壁上，以控制肉桂醛加氢的选择性。结果表明，在介孔氧化铝的孔壁上接枝氯丙基基团可以提高C= O键加氢的选择性。X射线光电子能谱表明，氯丙基接枝使Pd表面的负电荷移动。Pd的结合能和加氢选择性表现出良好的相关性，表明有机-无机协同催化。本研究所考察的另一体系，高活性固体酸催化剂也是有机-无机协同催化剂的原型。我们已经获得了在水介质中具有高活性的固体酸催化剂。该催化剂是<12><40>在介孔二氧化硅的纳米空间中由疏水性烷基基团包围的无机活性物种（H_3PW_0_聚氧乙烯酸酯分子）。疏水环境中的酸性质子对酯水解反应表现出最高的活性。介孔二氧化硅纳米结构提供了反应物分子和水的有效方法的活性位点的路径。本研究表明，在介孔二氧化硅纳米结构的基础上设计有机-无机协同功能是一种很有前途的新型功能材料的策略。

In this study, we investigated prototypic catalytic systems to demonstrate the advantage of a concept "Organic-inorganic cooperative catalytic system". One is Pd supported on mesoporous alumina with organo-modification to control selectivity for alpha-beta unsaturated aldehyde hydrogenation. Another system is a highly active solid acid catalyst comprising heteropolyacid inorganic molecules and hydrophobic mesoporous silica. In the former system, various organic molecules were grafted on the pore-walls of mesoporous alumina to control selectivity for cinnamaldehyde hydrogenation. It was found that the C=0 bond hydrogenation selectivity was improved by grafting chloropropyl groups on the pore walls of mesoporous alumina. X-ray photoelectron spectroscopy indicated that chloropropyl grafting brought about negative charge shifts of Pd surface. The Pd binding energy and the hydrogenation selectivity showed a good correlation, demonstrating an organic-inorganic cooperative catalysis. Another system investigated in this study, the highly active solid acid catalyst is also a prototype of organic-inorganic cooperative catalyst. We have achieved a solid acid catalyst highly active in aqueous media. The catalyst comprises inorganic active species (H_3PW_<12>0_<40> polyoxometalate molecules) surrounded by hydrophobic alkyl groups in the nanospaces of mesoporous silica. The acidic protons in the hydrophobic environment showed the highest activity for the ester hydrolysis reaction. The mesoporous silica nanostructure afforded paths for the efficient approach of reactant molecules and water to the active sites. The present study indicates that a promising strategy for novel functional materials is to design an organic-inorganic cooperative function on the basis of the mesoporous silica nanostructure.