Halogen‐Site Regulation in Cs<sub>3</sub>Bi<sub>2</sub>X<sub>9</sub> Quantum Dots for Efficient and Selective Oxidation of Benzyl Alcohol Driven by Solar Light
Ben Lei, Wen Cui, Jianping Sheng, Fengyi Zhong, Fan Dong
Abstract
Abstract Sluggish charge kinetics and low selectivity limit the solar‐driven selective organic transformations under mild conditions. Herein, an efficient strategy of halogen‐site regulation, based on the precise control of charge transfer and molecule activation by rational design of Cs 3 Bi 2 X 9 quantum dots photocatalysts, is proposed to achieve both high selectivity and yield of benzyl‐alcohol oxidation. In situ PL spectroscopy study reveals that the Bi─Br bonds formed in the form of Br‐associated coordination can enhance the separation and transfer of photoexcited carriers during the practical reaction. As the active center, the exclusive Bi─Br covalence can benefit the benzyl‐alcohol activation for producing carbon‐centered radicals. As a result, the Cs 3 Bi 2 Br 9 with this atomic coordination achieves a conversion ratio of 97.9% for benzyl alcohol and selectivity of 99.6% for aldehydes, which are 56.9‐ and 1.54‐fold higher than that of Cs 3 Bi 2 Cl 9 . Combined with quasi‐in situ EPR, in situ ATR‐FTIR spectra, and DFT calculation, the conversion of C 6 H 5 ‐CH 2 OH to C 6 H 5 ‐CH 2 * at Br‐related coordination is revealed to be a determining step, which can be accelerated via halogen‐site regulation for enhancing selectivity and photocatalytic efficiency. The mechanistic insights of this research elucidate how halogen‐site regulation in favor of charge transfer and molecule activation toward efficient and selective oxidation of benzyl alcohol.