光诱导卤代有机污染物碳卤键活化机理

Reductive activation of carbon-halogen (C-X) bond is the key step in the elimination of organic halide contaminants. Metal oxides based semiconductor photocatalytic hydrogenation is a promising strategy. However the precise pathways for cleavage/formation of C-X/C-H bond is yet to be established. In this proposal, model organic halides with characteristic structure/functioning groups will be used to explore the mechanistic details in light driven hydrogenation of organic halides on metal oxides interfaces, focusing on the sequence of electron transfer, proton transfer, as well as the intermediates associate with bond cleavage and formation. The unique C-X activation pathways, such as concerted multiple electron transfer, or the rate determining proton transfer, which distinguished from the dissociative single electron transfer and/or nucleophilic addition/substitution in other systems, will be discussed in terms of thermodynamics advantages, properties of electron/protons accumulated on metal oxides surfaces and the interactions of surface-substrate. With these knowledges, the photocatalytic transformation could be regulated by surface doping and defects. These studies will also provide fundamental guide for the development of more efficient photocatalytic systems for organic halides elimination.

碳卤键的还原活化是卤代有机污染物去除的关键步骤。目前认为碳卤键活化的路径包括解离单电子转移和亲核加成/取代。然而卤代有机化合物在金属氧化物表面还原转化的确切机理尚不明确。本项目将系统研究具有特定结构特征的模型卤代有机污染物的光(电)催化还原转化规律，阐明碳卤键活化的引发和速率控制步骤中的电子-质子转移顺序，例如同步多电子转移，同步质子耦合电子转移和质子加成等；识别碳卤键断裂和碳氢键生成过程涉及的中间体和过渡态构型。深入理解碳卤键活化机理与半导体界面电子、质子的存在形态和表面与卤代有机物之间作用模式的关系，并通过表面掺杂或引入缺陷等方式调控反应路径。确认影响脱卤程度和选择性的主导因素，为设计开发更高效去除有机卤代污染物的体系提供理论依据。

碳卤键的还原活化是卤代有机污染物分解去除过程的关键步骤。本项目旨在理解碳卤键活化的分子机制并通过光催化方法有效去除卤代污染物。结合动力学特征分析，表面修饰，反应分子探针，固体核磁和原位光谱等表征，建立了金属氧化物半导体及金属光催化材料界面不同的碳卤键活化机制，如电子转移、负氢转移或亲核进攻等；并进一步研究了表面配体或其它组分对碳卤键活化路径的影响。根据该步骤的难点和可行调控方法，设计了一系列光催化体系完成高惰性难降解卤代有机污染物的深度脱卤以及卤代有机物的高附加值转化。