乙苯在金属修饰的TiO2（110）表面碳氢键活化机理研究

Efficient, highly selective and “green” chemical synthesis process is urgently demanded considering the energy crisis and environmental problems human beings are currently facing. C-H activation is regarded as the direction of future development for synthetic chemistry, because it can convert hydrocarbon straightly to the required product. The present study mainly focus on the development of transition metal complex catalysts to improve the reaction efficiency and selectivity, and the surface chemical study of C-H activation is mostly on metal surface currently. The research of C-H activation using metal nanoparticles as catalyst is much less reported, which is however more suitable for large-scale industrial production. Thus this project intends to adopt ethylbenzene as model molecular to study the C-H activation catalyzed by metal particles supported on titanium oxide. Scanning tunneling microscope (STM) and temperature programmed stripping spectrum (TPD) combined with density functional theory (DFT) calculation will be employed to study the adsorption of ethylbenzene on rutile TiO2 (110), and the changes in reactive site, reaction efficiency and selectivity when different transition metal is deposited on TiO2 (110) surface, exploring the catalytic process of C-H activation catalyzed by metal particles from micro-scale. In addition, this project is expected to provide theoretic support for the design of new highly efficient catalyst by studying the influence of metal particle size, and the interaction between TiO2 (110) surface defect and metal on the C-H activation of ethylbenzene.

日益严峻的能源和环境问题要求更为高效、高选择性、“绿色”的化学合成方法。碳氢键活化可将天然碳氢化合物的C-H键直接断裂得到所需产物，是未来合成化学的发展方向。目前的研究主要集中在过渡金属络合物催化剂的开发以提高反应效率和选择性方面，且近年来利用表面化学方法研究碳氢键活化主要在金属表面进行；对于更适合大规模化工生产过程的金属颗粒催化剂研究则比较少。因此本项目拟采用乙苯作为模型分子研究其在金属颗粒修饰氧化钛表面的碳氢键活化，计划使用扫描隧道显微镜（STM）和程序升温脱附谱（TPD）并结合密度泛函理论（DFT）计算研究乙苯在金红石TiO2(110)表面的吸附，以及负载不同金属时反应活性位、反应效率和反应选择性变化，从微观尺度探索金属颗粒催化的碳氢键活化过程。此外，通过研究金属颗粒尺寸效应，以及TiO2(110)表面缺陷态与金属相互作用对乙苯碳氢键活化的影响，为设计发展新型高效催化剂提供理论支持。

日益严峻的能源和环境问题要求更为高效、高选择性、“绿色”的化学合成方法。碳氢键活化可将天然碳氢化合物的C-H键直接断裂得到所需产物，是未来合成化学的发展方向。目前报道的研究主要集中在过渡金属络合物催化剂的开发以提高反应效率和选择性方面，且近年来利用表面化学方法研究碳氢键活化主要在贵金属表面进行；对于更适合大规模化工生产过程的廉价金属氧化物催化剂表面研究则比较少。因此本项目采用乙苯作为模型分子，使用扫描隧道显微镜（STM）并结合密度泛函理论（DFT）计算，研究了其在金红石TiO2(110)表面的吸附以及光致碳氢键活化过程。实验发现，80K低温下，乙苯在氧化钛表面受紫外光激发可发生β-CH键断裂，选择性接近100%，且是一个两步过程。本研究为认识碳氢键活化微观机理提供了依据，并可为设计新型高效催化剂提供理论支持。