悬浮离子框架催化剂的设计合成与催化性质

This research program is aimed to develop novel suspended ionic framework catalysts and study their catalytic properties. We expect to synthesize anionic metal-organic frameworks (MOFs) in the presence of anionic organic bridging ligands or anionic guests, such as polyoxometalates (POMs). The anionic MOFs are used to synthesize suspended ionic framework catalysts by exchanging the endogenous extra-framework cations with exogenous catalytic-active metal ions inside the anionic pores. Suspending ionic metal sites inside the anionic pores of MOFs would eliminate the coordination of small balance anions, and result in maximum dangling bonds and empty d atomic orbitals to maximize the surface free energy and the valence electron activity of active metal sites. We expect to tune the catalytic properties of suspended ionic framework catalysts with different or mixed metal ions in the presence of different auxiliary ligands. To improve further the catalytic properties, we will introduce co-catalytic centers for synergistic catalysis. Assisted by the special nanoporous microenvironments, catalytic centers and co-catalytic sites, and the selective accumulation properties of pore channels toward reactant over product molecules, the catalytic efficiency and selectivity are expected to be highly improved through synergistic work, which should be much superior to the corresponding homogeneous molecular catalysts. We expected to study systematically the relationships between micro-structures and catalytic properties, and illustrate the specificity, characters and catalytic mechanisms of suspended ionic framework catalysts based on their crystal structures. We expect to set up a unique system for the synthesis of suspended ionic framework catalysts with unusual heterogeneous catalytic activity for the activation of inert small organic molecules under mild conditions.

本项目瞄准学科发展前沿，通过多学科的交叉与融合，提出了新型悬浮离子框架催化剂的设计合成与催化性质调控策略。拟以阴离子型有机桥联配体或杂多酸簇阴离子客体控制合成阴离子型金属-有机框架材料(Metal-Organic Frameworks, MOFs)，通过离子交换在MOFs阴离子孔道内引入活性金属离子，合成悬浮离子框架催化剂，防止抗衡阴离子占据催化活性位点，最大限度降低活性中心配位数，最大化表面能，增强价电子活性，提高催化效率。通过调节金属离子的种类与组成以及辅助配体调控催化性质，引进助催化组分协同活性中心催化，以MOFs纳米孔道作为微反应器，调控催化微环境与传输通道性质，保持微反应器中高反应物浓度，实现高效催化活化惰性有机物分子，得到数个具有特异催化性质的悬浮离子框架催化剂。系统研究微观结构与催化性质之间的关系，诠释悬浮离子催化反应的特异性和优点，深入研究催化反应机理。

本项目选择离子型框架材料为载体，或通过修饰将中性框架材料转变为离子型框架材料，引入离子型活性中性，使其悬浮在离子型框架材料的孔道中，实现了多相催化剂中的活性组分自由移动，有效解决了多相催化剂存在的问题，制备了一系列悬浮离子催化剂，并应用于多相热催化、光催化与电催化。通过调控催化活性中心微环境，以纳米孔道作为微反应器，引入辅助催化活性中心，结合纳米孔道效应，通过快速富集反应物和排出产物分子保持孔道中高反应物浓度，实现在温和条件下活化惰性反应物分子，取得了远优于传统多相催化的结果。以共价键取代配位键，以金属-有机框架材料（MOFs）为原料制备了新型有机框架材料，使所得材料继承了原MOFs的多孔骨架及性质，提高了催化剂的稳定性。以金属有机配位片段为模板，制备了新型多孔金属硅酸盐材料，为开发新型工业催化剂奠定了基础。实现了多次循环使用而不降低催化活性，并能保持催化剂组成与结构不变，拓宽了悬浮离子催化剂的使用条件范围。提出了微纳电池催化剂模型，为深入研究了催化反应机理，设计合成新型催化剂用于显著提高催化效率开辟了新途径，为进一步调控微观结构进而提高催化性能提供了依据。