双金属纳米粒子基核壳结构复合材料的可控制备及其性能研究

Noble metal based nanostructured composites have been attracting more and more significant concern because they are very promising for a wide range of applications in the field of optics, electronics, biology, catalysis, et al. However, until now their practical applications still remain big challenges and there are some unresolved problems, which can be ascribed to the following three possible reasons: (1) The resource of noble metals is relatively rare and expensive, leading to high production cost. (2) Noble metal nanoparticles tend to have high surface energy, leading to the easy migration and sintering of them into large sizes and poor stability. (3) It is hard to tune their performance in a wide range due to the limit in the single noble metal component. Aimming at the selective catalytic activation of C=O bonds in typical substrate molecules, this proposal suggests to design and fabricate the composites containing bimetallic cores by controlling the nucleation and growth process of the shell materials in the solution that have special modifier as the surface primers. It should be pointed out that using the bimetallic nanoparticles composed of noble metal and non-noble metal to replace the single noble metal nanoparticles will contribute to the decrease in the use of noble metals. Moreover, non-noble metal can tune the electronic structure of nobel metals in bimetallic composites, and change the coordinative environment of noble metals and the metal distribution on the surface, thus leading to the improved catalytic efficiency. Meanwhile, to improve the stability of individual bimetallic nanoparticles, porous materials are used as the supports to encapsulate single bimetallic nanopartile with the core-shell structures, in which the bimetallic cores are completely sorrounded by porous materals and thus promote the synergestic interaction between them. In this project, the mechanism of heterogeneous nucleation and growth including bimetallic nanoparticles and core-shell structure will be elucidated in detail, and the interfacial microstructures of both will be disclosed. By using different types of characterization methods and density functional theory (DFT), the influence of the microstructure of the core-shell structured composites on their catalytic performance based on the selective catalytic activation of C=O bonds in typical substrate molecules will be also studied. These will benefit us to understand the relationships including bimetallic nanoparticles and shell materials, and the structure and activity of the core-shell composites.

贵金属基纳米复合材料在光学、电学、生物和催化等领域展现出了一些优异的性能，然而，这类材料的实际应用仍存在一些问题，如贵金属相对稀缺且价格昂贵；贵金属纳米粒子具有高的表面能，稳定性较差；单一贵金属纳米粒子的性能调控空间有限等。针对上述问题，本项目拟以典型的选择性催化“C=O键活化”反应为出发点，设计和可控制备以非贵金属与贵金属的双金属纳米粒子为内核和多孔材料为壳层的核壳型复合材料。采用双金属代替单一贵金属不仅可以减少贵金属用量，而且可以调控贵金属的电子结构、改变其配位环境和表面元素分布，提高其催化效率。采用核壳结构可以避免纳米粒子的聚集和脱落，提高其稳定性；同时内核表面可与壳层完全接触利于两者间协同作用。本项目将重点探讨双金属之间以及双金属核与壳层的异相成核和生长机制，揭示双金属粒子与壳层间的界面微观结构。同时，结合多种表征手段和密度泛函理论，揭示双金属纳米粒子与壳层间的协同催化作用原理。

研究工作主要围绕着构筑以双金属纳米粒子为核和以多孔材料为壳的多功能复合材料，重点探讨核壳结构的形成机制；揭示双金属纳米粒子与壳层间界面微纳结构与其催化性能间的内在构效关系。已取得的创新性成果如下：1）以催化CO2与炔醇羧化环化为模型，构筑了多孔共轭微孔聚合物包覆AgAu双金属纳米粒子的空心三明治结构，利用双金属间的协同效应实现了高效催化转化制备α-亚烷基环状碳酸酯。2）以选择性氧化硫醚为模型，构筑了以AuPd双金属纳米粒子为夹层和以PCN-223(Mn)为壳层的三明治结构催化剂，AuPd双金属纳米粒子可以实现原位产H2O2作为氧化剂，同时与PCN-223(Mn)协同催化氧化硫醚高选择制备亚砜。3）以选择性加氢反应为模型，利用UiO-67(Zr)可控包覆Pd纳米粒子构筑三明治结构催化剂，限域孔道中通过两者协同实现了对底物炔烃的富集及其高选择性转化制烯烃；进一步，利用UiO-66(Zr)可控包覆Pd1Cu4双金属纳米粒子构筑三明治结构催化剂，实现了原位产氢，同时高选择转化3-硝基苯乙烯制备3-氨基苯乙烯；此外，还利用MIL-101(Cr)包覆PtNi双金属纳米粒子，实现了串联催化苯酚加氢制备KA油，Ni位点可以显著增强Pt的催化活性。该系列研究工作可为新型双金属纳米粒子基核壳型纳米催化剂的设计和可控制备提供新思路。截至目前，在面上项目的资助下，共发表论文10篇，包括Science Advances（1篇）、Angewandte Chemie International Edition（2篇）、Advanced Materials（1篇）、Advanced Energy Materials（1篇）、Journal of Materials Chemistry A（1篇）等，申请发明专利5项。