多溴联苯醚碳溴键界面光化学还原断裂机理

The mechanism detail of photoinduced interfacial reductive cleavage of carbon-halogen bond (C-X + 2e- + H+ → C-H + X-) will be investigated on cuprous oxide(Cu2O) and titanium dioxide, with polybrominated diphenyl ethers (PBDEs) as targeting substrates. The visible light driven reductive debromination is proposed on p-type Cu2O based on its bandgap and conduction band potential. The reaction pathways on TiO2 and Cu2O will be illustrated systematically, with focus on interfacial electron transfer dynamics between C-X bond and conduction band electrons at different energetic level. The electron transfer is coupled by proton transfer: concerted electron proton transfer or sequential electron-proton transfer. The two possibilities could affect fundamentally the debrominiation products distribution and reaction kinetics. The morphology controlled dynamics of charge (electron and hole) separation, recombination and electron accumulation efficiency correlated to the observed debromination efficiency. These studies will provide mechanistic insight for the environmental significant C-X cleavage process in halogenated organics, also the strategies for their reductive degradation under visible light irradiation.

本项目将研究多溴联苯醚等卤代有机物中碳卤键的还原断裂(C-X + 2e- + H+→ C-H + X-)机理。利用p型氧化亚铜(Cu2O)的可见光响应和强还原性的导带电子，实现此类化合物在可见光下的转化脱毒。综合Cu2O和TiO2 这两类典型体系中的结果，得到可见光和紫外光下C-X键在不同界面断裂的机理细节，特别是处于不同能级的导带电子与C-X的这一反应决速步的动力学，重点研究该过程中质子的参与方式（同步的质子耦合电子转移或分步的电子-质子转移等）。考察半导体微观型貌和界面光生空穴电子的分离/累积效率与表观光活性的关联。加深对光引发碳卤键断裂这一重要环境过程的理解，并总结出提高光还原转化效率的关键因素。

本项目选择了典型的卤代有机污染物（如多溴联苯醚、卤代羧酸等）作为目标化合物，采用还原加氢的方式实现这些污染物的光催化转化降解。确认了半导体界面活化碳卤键的活性位点，证明了光催化还原脱卤与界面电子转移驱动力的关联以及表面羟基作为质子给体参与脱卤加氢的动力学行为。利用氧化物表面金属铜纳米粒子与底物的相互作用经由內界电子转移促进卤代化合物碳卤键活化，使光催化转化速率提高达一个数量级。开发了具有高能级导带的一价铜-苯乙炔配位聚合物纳米材料实现了卤代化合物在可见光照下的还原加氢。在Adv. Mater., Appl. Catal. B: Environ.等国际SCI期刊上发表相关论文6篇。