基于氮杂环sp3 C-H键选择氧化的碳基非贵金属催化剂可控制备与性能研究

As an important branch of C-H bond activation, selective oxidation of sp3 C-H bond in nitrogen heterocyclic compounds has an important position in medicine, food and chemical industry, in which selective oxidation of sp3 C-H bond in methyl pyridine is the most representative. In this research plan, nonprecious metal nanoparticles coated with nitrogen-doped carbon materials (M@NC) which has been designed as an advanced and novel catalyst for oxidative reaction of alcohols to esters is chosen as a catalyst and used in selective oxidation of sp3 C-H bond in methyl pyridine, with the aim of precise regulating the thickness of nitrogen-containing carbon layer and the type of coated metal to investigate the catalytic performance of M@NC. For the purpose of avoiding the uncontrollability of the M@NC structure caused by the method of thermolysis of the mixture of carbon and nitrogen precursors and metal precursors, this project manages to synthesize M@NC with controllable structure via post-treatment cladding nitrogen-containing carbon layers on the surface of the supported metals, and understand the relationship between physicochemical property of M@NC and the thickness of nitrogen-containing carbon layer and the type of coated metal. Further, M@NC with various factors is used to catalyze selective oxidation of sp3 C-H bond in methyl pyridine molecule. Efforts will be directed to understand the physicochemical mechanism in the corresponding conversion processes, seek and fabricate highly efficient catalytic system for selective oxidation of sp3 C-H bond in nitrogen heterocyclic compounds, and thus providing guidance and reference for developing new technologies for transformation of sp3 C-H bond in nitrogen heterocyclic compounds.

氮杂环sp3 C-H键的选择氧化是C-H键活化领域内一个重要的分支，在医药、食品和化工中具有不可忽视的地位，其中以甲基吡啶sp3 C-H键的选择氧化最具代表性。本项目以甲基吡啶sp3 C-H键的选择氧化为探针反应，选取近年来在醇的氧化酯化反应中表现良好的氮掺杂碳包覆非贵金属材料（M@NC）作为催化剂，目标在于精准调控含氮碳层的厚度和被包覆金属的种类来研究M@NC的催化特性。为避免以往采取热解碳氮前驱体与金属盐前驱体混合物的方法所导致的M@NC结构的不可控性，本项目主要采用先负载金属再包覆含氮碳层的方法来调控M@NC的结构，并理解M@NC的理化性质与所包覆金属的种类和含氮碳层厚度之间的关系。进一步地，围绕甲基吡啶sp3 C-H键的催化氧化，探究不同因素水平的M@NC的催化性能，研究相关过程中的物理化学机制，筛选和创制高效的催化剂，为发展氮杂环sp3 C-H键多相催化转化新技术提供参考依据。

纳米碳材料具有较高的比表面积、丰富可调的表面化学性质，且容易大批量合成，同时环境友好，因此，纳米碳材料不仅可以作为金属活性组分的载体，而且可以直接作为催化剂广泛应用于催化化学领域。氮杂环sp3 C-H键的选择氧化是C-H键活化领域内一个重要的分支，在医药、食品和化工中具有不可忽视的地位，其中以甲基吡啶sp3 C-H键的选择氧化最具代表性。虽然纳米碳材料或杂原子（氮、氧等）掺杂/修饰的纳米碳材料在环己烷、苯乙烯、甲苯/乙苯等C-H键的选择性氧化反应中都有一定的应用，但是这些碳催化体系多使用H2O2或TBHP作为氧化剂，才能在较温和的条件下使C-H键活化。然而在氧气作为氧化剂的条件下， 纳米碳催化剂并不能高效地将C-H键选择性活化。基于此，本项目针对纳米碳材料的可控设计（制备具有单一石墨氮结构的多孔碳材料并应用于乙苯的选择氧化）和杂原子修饰的多孔碳材料催化C-H键氧化氨化为主要内容展开研究。其中，纳米碳材料直接作为催化剂在氧气作为氧化剂的条件下可以将含氮杂环化合物中sp3 C-H键选择氧化氨化为相应的酰胺化合物是本项目所取得的重要进展。