63. Efficient Benzylic C–H Bond Activation over Single-Atom Yttrium Supported on TiO2 via Facilitated Molecular Oxygen and Surface Lattice Oxygen Activation

Zhen Xue, Jiangrong Yang, Lina Ma, Hongchu Li, Lan Luo, Kaiyue Ji, Zhenhua Li, Xianggui Kong, Mingfei Shao, Lirong Zheng, Ming Xu,* and Haohong Duan*
ACS Catal. 2023, 14 (1), 249-261.
DOI: 10.1021/acscatal.3c04484

Abstract
Selective activation of C(sp³)–H bonds is important for value-added chemical production, but it remains challenging to proceed under moderate conditions. Herein, we report single-atom yttrium supported on TiO₂ (Y₁/TiO₂) as a catalyst for photocatalytic benzylic C–H bond activation at room temperature. In toluene oxidation, it exhibits a toluene conversion rate of 850 μmol g^–1 h^–1 with a high benzaldehyde selectivity of 94.1%. Experimental data show that abundant Y₁^δ+–O–Ti³⁺ (δ > 3) sites are formed at the interface with strong electronic metal–support interactions, inducing highly spin-polarized electrons that facilitate charge separation. Furthermore, the single-atom Y species promote the formation of oxygen vacancies and lead to lattice distortion on TiO₂, which facilitates molecular oxygen and surface lattice oxygen activation. These reactive oxygen species can directly react with benzyl radical under light irradiation to produce benzaldehyde and hence increase the photocatalytic performance. This work shows the great potential of rare-earth single-atom catalysts in C(sp³)–H bond activation under mild conditions driven by renewable solar energy.