类贵金属CoN@C催化剂可控制备及其催化伯醇和仲醇氧化偶联制备α,β-不饱和酮反应的研究

α,β-unsaturated ketones are key intermediates widely used in pharmaceutical, agrochemical, perfume and other fine chemical industries. The traditional synthesis of α,β-unsaturated ketones suffer from poor selectivity and low atomic economy. On this ground, this project aim to develop a “one-pot” strategy to produce α,β-unsaturated ketones through aerobic oxidative coupling of primary and secondary alcohols, and to explore a type of “platinum-like” CoN@C based catalysts with uniform composition that are expected to be highly active and selective for the target reaction. In this project, we will combine experimental and theoretical methods, (1) to study the effect of different preparation parameters on the structure and composition of CoN@C based catalysts, and the catalytic performances of CoN@C catalysts in aerobic oxidative coupling of primary and secondary alcohols to produce α,β-unsaturated ketones, meanwhile by combining the characterization results to clarify the structure-performance relationship, in order to realize the controllable synthesis of highly active and selective CoN@C based catalysts; (2) to investigate the adsorption and activation behavior of O2 on the active species of CoN@C catalysts by DFT calculations, in order to expand the application of CoN@C catalysts into other oxidative transformations. This program will not only contribute to the understanding the catalytic behavior of “platinum-like” CoN@C catalysts in aerobic oxidative reactions, but also provide a practical avenue for the development of efficient noble-metal-free catalysts for green synthesis of α,β-unsaturated ketones.

α,β-不饱和酮是重要的有机合成中间体，广泛应用于医药、农药、香料等精细化学品合成中。鉴于传统的合成方法存在选择性差、原子经济性低等缺点，本项目提出以伯醇、仲醇、O2为原料，“一锅”制备α,β-不饱和酮的新途径，并为该反应设计制备兼具高活性和高选择性且组成单一的类贵金属CoN@C催化剂。以实验和理论相结合的方法，（1）考察不同的制备参数对催化剂组成和结构的影响规律，并以伯醇和仲醇氧化偶联制备α,β-不饱和酮为目标反应对催化剂进行活性评价，同时结合先进的表征技术，研究催化剂结构、组成与性能之间的关系，以实现高活性CoN@C催化剂的可控制备；（2）通过理论计算研究催化剂对O2的吸附活化行为，为拓宽在其它氧化反应中的应用提供理论依据。所得研究结果，在基础研究领域将加深对CoN@C催化剂具有“类贵金属”催化行为的认识，在工业应用方面将为α,β-不饱和酮的合成提供新的方法和高效的非贵金属催化剂。

Co(Fe)-N-C材料在电化学及精细化学品合成中展现出优良的催化性能，但对其真正催化活性物种的认识仍存在争议。本项目以伯醇和仲醇氧化偶联合成α,β-不饱和酮、芳香硝基化合物选择性加氢等为探针反应，借助HAADF-STEM、XAFS等先进表征手段和对照实验，对Co(Fe)-N-C催化剂真正催化活性物种及其配位结构进行了系统研究。（1）实现了以Co-N-C/CMK-3为催化剂，通过伯醇和仲醇氧化偶联的方法制备α,β-不饱和酮，并证明催化剂中Co纳米颗粒无催化活性，而Co单原子是真正催化活性中心；（2）制备出Co完全以单原子形式存在的Co-N-C催化剂，实现了芳香硝基化合物选择性加氢制备偶氮化合物，并借助DFT计算和XAFS拟合的手段解析出Co单原子中心的配位结构；（3）制备出Fe完全以单原子形式分散的Fe-N-C催化剂，实现了温和条件下C-H键选择性氧化制备醛（酮）类化合物。并借助穆斯堡尔谱和选择性毒化实验，证明Fe单原子中心存在多种配位结构，其中Fe-N5物种的活性比其它物种（Fe-N4, Fe-N6）高3-11倍，然而其含量仅占20%，为更高活性Co(Fe)-N-C催化剂的制备指明方向。本项目的实施，在基础研究领域加深了对Co(Fe)-N-C这类单原子催化剂构效关系的认识，在工业应用方面为α,β-不饱和酮、偶氮化合物的制备提供了绿色环保的合成路径。