氢键驱动钒氧簇基分子笼自组装构建多孔分子材料及其催化性能研究

The polyoxovanadate-based metal-organic cage (VMOC), which has sufficient intrinsic porosities and catalytic sites, is an ideal building block for the molecular porous material (MPM). However, its catalytic application is impeded by the self-assembly of VMOC and its counter-ion in a close-packing manner which can inevitably lead to the shield of its pores and catalytic sites. This project focuses upon using the charge-assisted hydrogen bond between ammonium and oxyanion as the driving force for the self-assembly of VMOC and metallocyclam/cyclen to generate the MPM catalyst with sufficient catalytic sites and intrinsic/extrinsic porosities. The catalytic property of the prepared catalyst will be evaluated in the context of the selective alcohol oxidation reaction. This project is mainly concerned on critical scientific problems including the hydrogen bond-driven self-assembly principle between VMOC and metallocyclam/cyclen and synergistic catalytic effect between building blocks. The specific research contents are the synthetic approach of VMOC and the self-assembly behavior between VMOC and metallocylam/cyclen, then the structure-property correlation with respect to the selective oxidation of alcohols will be uncovered. Furthermore, varieties of characterization techniques will be utilized during the evaluation of catalysts in order to investigate the catalytic mechanism in terms of both molecular level and reaction kinetics. The success of this project will provide the scientific support for both fundamental and applied aspects of MPM in the field of catalysis.

钒氧簇基金属有机分子笼（VMOC）具有丰富的本征孔和催化活性位，是制备多孔分子材料（MPM）的理想构筑单元。但VMOC与抗衡阳离子之间的自组装过程不可控，易形成密堆积结构，导致孔道和催化活性位被屏蔽，限制其在催化反应中的应用。本项目提出以铵根离子与氧阴离子形成的电荷辅助氢键驱动VMOC与抗衡阳离子金属大环多胺自组装的方法，制备具有丰富本征孔、外源孔和催化活性位的MPM催化剂，再以醇选择性氧化作为探针反应考察催化剂性能。围绕VMOC与金属大环多胺之间氢键驱动的自组装机理、构筑单元的协同催化作用等关键性科学问题，研究不同VMOC的合成方法以及VMOC与金属大环多胺的自组装规律，实现MPM催化剂的可控合成。探索MPM催化剂在醇选择性氧化反应中的催化性能，揭示催化剂结构与性能的关系。利用多种反应表征手段，从分子水平和反应动力学两方面阐明催化反应机理，为MPM在催化领域的发展与应用提供科学支撑。

金属氧簇具有丰富的催化活性位，是构筑配位分子笼和金属有机骨架的理想构筑单元。本项目主要研究催化剂中钒氧簇、碱土氧簇等金属氧簇的结构调控方法，明确制备过程中的结构演化机制以及与客体分子的相互作用，评价催化剂在加氢、氧化、聚合、水解等反应中的催化性能，通过原位、准原位的技术手段揭示催化反应机理。通过本项目的顺利实施，开发了节点-连接体匹配、离子交换后修饰等策略分别调控钒氧簇和镁氧簇结构的有效方法；针对配位分子笼和金属有机骨架结构稳定性弱的问题，开发了“纳米浇筑-热处理”组合策略，将金属氧簇转化为介孔氧化硅镶嵌的纳米颗粒催化剂，在抗生素水解反应中展现出远高于传统催化剂的催化性能。面向新型催化材料的成型，开发“交联共聚-超临界干燥”组合策略，实现铜氧簇基配位分子笼的原位合成和凝胶成型。成型催化剂中配位分子笼基本实现单分散，在环氧丙烷与二氧化碳环加成反应中呈现出较高的催化性能和重复使用性。基于上述催化材料的开发策略，分别针对异丁烯与乙二醇加成的连串副反应、异丁烯与羧酸加成的平行副反应，对催化剂活性位和孔道结构进行设计。通过探索性数据分析方法、原位表征技术、分子模拟手段的综合运用，揭示了催化剂孔道结构乙二醇单叔丁基醚选择性的影响规律，以及锆氧簇基催化剂表面原料和反应中间体的相对密度差异对羧酸叔丁酯选择性的影响规律，进而构建环保涂料用绿色溶剂和酯类单体的原子经济催化反应工艺。