基于瓜环的贵金属纳米催化剂的制备及其在(杂)芳环C-H活化反应中的催化性能研究

Since nanomaterials have unique advantages compared to traditional catalytic materials, they are attractive candidates for use as catalysts with the most promising future. Now，exciting new opportunities are emerging in the field of catalysis based on nanotechnology approaches. Presently，fundamental understanding of mechanism of nanocatalysis as well as rational design and fabrication of nanocatalysts with extremely high activity and selectivity, long lifetime, and low energy consumption are key objectives of nanocatalysis. Cucurbit[n]uril(CB[n]) is a family of macromolecules and has gain much attention in recent years for their unique structural features and physicochemical properties. These distinguishing features ensure a potential applications in nanocatalysis for CB[n]. This project will design and synthesize nanocatalysts for direct functionalization of (hetero)arenes by C-H bond cleavage by using CB[n] as protecting agents and support with liquid phase methods.. This goal can be achieved by precisely controlling the size, shape, spatial distribution, surface composition and electronic structure of the nanocatalysts. Through this project to explore the fabrication conditions for nanocatalysts with high activity and selectivity, such as changing reducing agents, the molar ratio of CB[n] and metal precursor, the speed of nucleation and growth. This project also intend to reveal the relationship between the structure and catalytic properties of nanocatalysts, the mechanism of nanocatalysis, and the potential role of CB[n] in nanocatalysis. Through the systematically studies, we render the experimental data and scientific basis for nanocatalysis in direct C-H bond activation and the application of CB[n] in nanotechnology.

相对于传统催化材料，纳米材料的独特优势使其在催化领域极具光明前景。而纳米科技的发展也为纳米催化领域带来了新的契机。目前，揭示纳米催化机理以及合理设计并制备高效、高选择性，能够多次循环使用以及低能耗的纳米催化剂是纳米催化领域的主要任务。瓜环是近年来备受瞩目的大环状化合物，其独特的结构特征和物理、化学性质使其在纳米催化领域具有潜在的优势。本项目拟采用液相合成法，采用瓜环作为载体和保护剂，设计并制备出形貌可控的贵金属纳米催化剂，催化(杂)芳环碳-氢活化官能团化反应。通过对还原剂种类、瓜环与金属前驱体之间的比例、成核速度、生长速度等动力学因素的调节来探索高效高选择性纳米催化剂的制备条件；并深入研究纳米催化剂的结构和性能之间的构效关系，探索纳米催化机理以及瓜环在催化过程中的作用。这为瓜环在纳米科技领域中的应用以及纳米催化剂在直接碳-氢活化官能团化反应中的应用提供实验依据。

本项目成功制备了一系列基于瓜环的贵金属纳米颗粒作为有机合成反应的催化材料。该催化材料在C-H活化官能团化反应中，展示了优于市售钯炭催化剂以及传统均相催化剂的催化活性、选择性和稳定性，能够多次循环利用且活性得以维持。瓜环是一类具有刚性结构的大环状分子，其独特的结构特征和物理、化学性质使其在纳米科学领域有着潜在的优势。本项目采用简单的一锅液相合成法，利用瓜环作为载体和保护剂，制备出一系列分散均匀、粒径均一可控的金属纳米颗粒，并且通过IR、XRD、TEM、NMR等表征手段的表征详细的研究了不同元数瓜环对金属纳米颗粒形貌的影响。通过对还原条件的调节，例如，温度，还原剂，金属前躯体和瓜环投料比等，就可以实现对金属纳米颗粒形状的控制，合成了近似球形、立方体、锥形以及表面富含缺陷的纳米花等结构。基于瓜环的纳米催化剂在含氟芳烃化合物以及吲哚类杂芳烃的这两类化合物C-H键活化官能团化反应中均表现出较高的催化活性、稳定性和官能团容忍性。通过对照试验，异相催化的反应机理得到了验证。该催化剂能够多次循环使用，成功的解决了传统Pd盐均相催化剂不能回收利用的问题以及市售的Pd/C异相催化剂容易团聚失活的问题。更为重要的是我们开发的催化体系比均相反应的条件温和，对湿度和温度不敏感，在普通的外界条件下就能以极小的催化剂用量实现该反应，这为实际工业生产提供了一个新的选择。本项目经过三年的执行，解决了基金申请之初所提出的科学问题，发表了高水平的学术论文并申请了专利，达到了预期的目标。