基于MOF限域高负载量单原子催化剂的设计制备及其芳香硝基化合物选择加氢性能研究

The single-atom catalysts, owning the unique property of atomtic dispersion and 100% atom utilization, show excellent performance in many fields, especially in heterogeneous catalysis. At present, the metal loading of single atom catalysts is low, which restricts their practical application in industry. So, it is imperative to develop the high metal loading and stable single atom catalysts. On this ground, this project aims to develop single atom catalyst with high metal loading based on MOF confinement, which is expected to show both high activity and high selectivity for the chemoselective hydrogenation of substituted nitroaromatics. In this project, we will combine experimental and theoretical methods to study：(1) the effects of preparation parameters on the dispersion/aggregation of supported metal single atoms, so as to uncover the stabilizing mechanism of metal single atoms on the support and finally to accomplish the controllable preparation of supported single atom catalysts with high metal loading; (2) the catalytic performances of the obtained catalysts for the chemoselective hydrogenation of substituted nitroaromatics, in order to reveal the structure-performance correlationship. These studies will provide scientific basis for the design and development of a highly active, selective, and practical catalyst for the chemoselective hydrogenation of substituted nitroaromatics. This project will not only contribute to the understanding the stabilizing mechanism of high loading metal single atoms, but also provide a highly effective catalyst for the green production of substituted anilines.

单原子催化剂因具有原子分散性、活性原子利用率100%的独特优势，在诸多领域尤其是多相催化方面表现优异。目前单原子催化剂中活性中心金属浓度普遍偏低，限制其实际工业化应用，因此亟需发展高负载量、分散稳定的单原子催化剂。本项目针对含易还原基团芳香硝基化合物选择加氢反应，采用MOF限域的方法设计制备高负载量单原子催化剂。以实验和理论相结合的方法:（1）考察催化剂制备参数对单原子分散/团聚行为的影响，揭示单原子在载体上的稳定机制，为实现高负载量单原子催化剂的可控制备提供理论指导；（2）考察催化剂在含易还原基团芳香硝基化合物选择加氢反应中的催化性能，研究催化剂结构、组成与性能之间的关系，为实现芳香硝基化合物选择加氢提供科学基础。本项目的实施，在基础研究领域将加深高负载量单原子稳定机制的认识，在工业应用方面将为取代基芳胺的合成提供一种新型高效催化剂。

负载型催化剂由于其独特物理化学性质在精细化学品合成中表现出优异的催化性能，但仍存在活性中心稳定性问题。本项目以芳香硝基化合物选择加氢和氢甲酰化等为探针反应，借助HAADF-STEM、XAFS等先进表征方法，对MOF限域负载型催化剂及其催化性能进行系统研究：（1）考察了在PtO2/Fe2O3前驱体表面原位生长MIL-100(Fe)，研究发现由于配体酸性弱，未能有效在前驱体表面原位生长MIL-100(Fe)；（2）制备了Rh/ZnO@ZIF-8催化剂，XPS、SEM等研究表明ZIF-8壳层的存在有效抑制了催化剂在高碳烯烃氢甲酰化反应中金属Rh的流失，提高催化剂的稳定性；（3）制备了Ru/ZnO@N-C-ZnO催化剂，多孔N-C-ZnO壳层的构建不仅有效抑制了Ru纳米粒子长大，同时促进了反应底物与活性中心的接触，在对氯硝基苯的选择加氢反应中表现出优异性能，循环使用20次，活性和选择性没有下降；（4）采用发泡法制备了Co@NC催化剂，结合XAFS、XPS、HAADF-STEM等表征证明催化剂中Co-N物种含量可通过催化剂热解温度进行调控，研究发现在3-硝基苯乙烯的选择加氢反应中催化剂Co-N物种含量与催化活性成正相关。本项目的实施，在基础研究领域加深了MOF限域活性组分构效关系的认识，在工业应用方面为功能化苯胺、高碳醇的制备提供了绿色环保的合成路径。