多金属氧簇为结点构筑多孔杂化材料及其催化性能研究

This project aims to combine polyoxometalate (POM)-based materials and metal-organic framework (MOF) materials and obtain porous POM-based MOF materials with tunable sizes by adjusting the ε-Keggin units (monomeric, dimeric and polymeric anions) and organic ligands (including azole ligands, benzene carboxylic acids, metalporphyrin fragments and so on). It is desirable to obtain POM/metalporphyrin hybrid materials once metalporphyrin and their derivatives that widely used as enzyme to simulate catalysis were introduced to this system. Such materials would take the advantages of the redox activity of POM units and the enzymatic property of metalporphyrin fragments, achieving the dispersion and immobilization of catalytic centers at the molecular level. It would be bridge the gap between POM-based MOF materials and enzyme. This kind of materials possesses discrete multi-metal site and dynamic host-guest response, which would be a biomimetic catalyst. We will investigate the catalytic activity of such materials in the oxidation of toluene and its derivatives. It is desirable to solve some technical difficulties suffered from during the catalytic process, such as, low conversion, poor catalytic activity and so on. The synthetic method, structure-function relationship of this kind of catalysts that perhaps influence on catalytic oxidation of the side chains of aromatic compounds to prepare aromatic aldehydes, aromatic acid and other important organic intermediates, will be explored. We can simulate the catalytic mechanism by using computational methods. The aim of this project is to seek a road of fast catalytic oxidation of toluene and its derivatives under mild conditions, and obtain a biomimetic catalyst that can be recycled for many times. This provides theoretical and experimental basis for the development and application of porous POM-based MOF materials as a new type of biomimetic materials.

本项目拟将多酸材料和MOF材料结合，通过调控ε-Keggin单元（单体、二聚体及多聚体）与有机配体（唑类、苯羧酸类及金属卟啉类）来制备孔尺寸可调的多酸基MOF晶体材料。在有机基元方面通过引入广泛用于模拟酶催化的金属卟啉化合物，期望构筑多酸-金属卟啉杂化材料。结合多酸的氧化还原特性和金属卟啉片段的酶特性，以实现催化中心在分子水平上的分散与固载，有望建立多酸基MOF材料与酶之间的桥梁。这类材料具有孤立的多核位点及动力学主客体响应特性，有望成为仿生催化剂；我们将研究这类材料在氧化甲苯及其衍生物中的催化活性，期望解决催化过程中催化活性差、转化率低等问题。探讨这类催化剂的合成方法、构效关系对其在催化氧化芳烃侧链中的影响；并利用理论计算研究仿生催化机理。本项目可寻求一种在温和条件下快速催化氧化甲苯及其衍生物，并可以多次重复使用的仿生催化剂。为多酸基MOF作为新型仿生材料的开发应用提供理论和实验依据。

本项目选择不同功能性的刚性或半刚性有机配体与基于ε-Keggin的纳米多酸簇单元为研究对象，以期得到具有不同孔尺寸的多酸基晶体材料。结合多酸的氧化还原特性和有机片段的特性，以实现催化中心在分子水平上的分散与固载，有望建立多酸基MOF材料与催化剂之间的桥梁。摸索构筑多孔多酸基配位材料的自组装条件，并探索所构筑的配位框架材料的催化性能。我们得到了一系列基于ε-Keggin单元的无机-有机杂化多孔材料，通过元素分析、FT/IR及单晶X-射线衍射等手段对制备的多酸基晶体材料进行结构表征；优化反应条件，提高产率，为下一步研究催化反应做好准备。然后，通过扫描电镜（SEM）、XPS、ICP、X-射线粉末衍射对催化反应前后的催化剂及反应产物进行表征，寻找活性较高的多酸晶体催化剂。总结已有成果中结构与性能间的构效关系，进一步设计优化配位材料结构，为制备具有优异催化特性的多酸基多孔材料的开发应用提供理论和实验依据。