“动态模板”法可控构筑多级孔硅氢化合物材料及其作为贵金属催化剂载体的应用研究

This project aims at the synthesis of hierarchically porous hydridosilsesquioxane (HSQ) materials and their application as scaffold of noble metal nanoparticles. To accomplish our goal, hierarchically porous HSQ materials are firstly synthesized through “dynamic template” of organic mesomorphous complexes formed by polyelectrolyte (poly(ethylene oxide)-b-poly[N-(4-vinylbenzyl)-N,N’-diethylamine hydrochloride] (m-PEO-b-PVEAH)) and cationic surfactant (N-lauroylsarcosine sodium (Sar-Na)). The key of the design involves: 1) the hydrogen bonding between the ether oxygens of m-PEO chain and trialkoxysilane benefits to the stability of the HSQ during the hydrolysis process; 2) the hydrolysis of the trialkoxysilane precursors in acid condition generates positively charged silica oligomers, the inorganic species will disturb the electrostatic interactions between PVEAH chains and the anion surfactants which makes the phase separation of PVEAH chains and therefore forms a dynamic template. In our strategy, the m-PEO chain and the anion surfactants act as the mesoporous template while the phase separated PVEAH domains act as the secondary nanoporous template. The morphologys and meso-structures of the synthesized hierarchically porous HSQ materials originate from the mesomorphous complex of m-PEO-b-PVEAH/Sar-Na. By adjusting the molecular weight, chain length of the polyelectrolyte, the molar ratio of polyelectrolyte and surfactant, and reaction factors such as synthesis temperature, pH value, hierarchically porous HSQ materials with well-defined morphologys and meso-structures and controllable pore size will be prepared and the synthetic mechanism will be revealed.. Ascribe to the inherent Si-H group and the hierarchically porous structure, the synthesized HSQ materials are used as both the scaffolds and mild reducing agent for the immobilization of noble metal nanoparticles. The advantages of the hierarchically porous HSQ materials lie in: first, without using of other reducing agent simplifies the catalyst preparation process; second, the ordered mesopores in HSQ materials can effectively trap and capture the noble metal nanoparticles avoiding the loss of catalyst during the catalytic process; third, the large pores in HSQ materials can act as the warehouse of the reactant which benefit to the concentration of the reactant and therefore enhance the catalytic property. The structure-activity relationship of the morphology, meso-structure and pore size of HSQ materials with the immobilization efficiency and catalytic property of the noble metal nanoparticles will be explored by choosing the catalytic hydrogenation of nitrobenzene in water as a typical example.. This project is anticipated to develop a new strategy for the synthesis of hierarchically porous HSQ materials and offer a potential theoretical guidance for the application HSQ materials in catalysis.

本项目旨在建立一种多级孔HSQ材料可控构筑的新方法，并研究多级孔HSQ材料作为贵金属催化剂载体的应用。为此，拟采用“动态模板”方法，即以聚环氧乙烷-b-聚4-乙烯苯基-N,N’-二乙基胺盐酸盐嵌段共聚物为阳离子聚电解质，N-十二烷基肌氨酸钠为阴离子表面活性剂，利用m-PEO-b-PVEAH与Sar-Na形成的介晶复合物为模板，制备多级孔HSQ材料。通过系统研究，阐明多级孔HSQ材料的合成机制，探索出一条多级孔HSQ材料可控构筑的新方法。以多级孔HSQ材料为载体和还原剂，研究贵金属纳米催化剂在其孔道内部的固载情况，开发一种简单高效的负载型贵金属纳米催化剂的制备体系。以水相中硝基苯的催化氢化为模型反应，考察负载型贵金属催化剂的催化性能，揭示多级孔HSQ材料在贵金属纳米催化剂负载中载体材料与催化性能之间的构效关系，拓展HSQ材料在催化领域中的应用。

以带相反电荷聚电解质-表面活性剂形成的复合物介晶为模板，“动态模板”方法可控合成多级孔二氧化硅材料。系统研究反应条件如电解质、表面活性剂、硅源种类以及比例对产物形貌及孔结构的影响，系统总结了影响规律，揭示了多级孔二氧化硅合成机制;以合成的多级孔二氧化硅材料为载体，研究其固载贵金属催化剂（Pd、Ti、Ni-Co合金等）以及生物催化剂（生物酶）的能力，并评价相关催化剂的催化性能。研究表明：1）该方法具有较好的普适性，多种聚电解质与表面活性剂复配体系可成功制备多级孔二氧化硅材料，而且该方法可以拓展至多级孔碳微球的合成；2）硅源种类对多级孔二氧化硅材料的形貌影响显著，通过引入带正电荷的氨基硅源，打破体系的电荷平衡及各物种的组装，成功制备出空心结构多级孔二氧化硅材料；3）基于多级孔道结构有利于物质在材料内部的传输，该材料显示出优异的负载性能，而且制备的异相催化剂显示出良好的催化活性。