Intensifying Photocatalytic Baeyer–Villiger Oxidation of Ketones with the Introduction of Ru Metalloligands and Bimetallic Units in POM@MOF
Jing Wang, Jing Wang, Luoning Li, Yanan Liu, Zelong Yuan, Sha Meng, Pengtao Ma, Jingping Wang, Jingping Wang, Jingyang Niu
Abstract
The synthesis of visible light-responsive and efficient photocatalysts toward green Baeyer–Villiger oxidation organic synthesis is of extraordinary significance. In this work, we have synthesized two examples of visible light responsive crystalline polyoxometalate@metal–organic framework materials Ru-NiMo and Ru-CoMo by introducing Ru metalloligands and {CdM 3 O 12 } bimetallic units (M = Ni or Co). This is the first report of metalloligand-modified polyoxometalate@metal–organic framework materials with bimetallic nodes, and the materials form a three-dimensional framework directly through coordination bonds between {CdM 3 O 12 } bimetallic units and metalloligands. In particular, Ru-NiMo can achieve efficient photocatalytic conversion of cyclohexanone to ε-caprolactone in yields as high as 95.5% under visible light excitation in the range of λ > 400 nm, achieving a turnover number and turnover frequency of 955 and 440 h –1, respectively, which are the best known photocatalysts for Baeyer–Villiger oxidation, while apparent quantum yield measured at 485 nm is 4.4%. Moreover, Ru-NiMo exhibited excellent structural stability and recyclability, producing a 90.8% yield after five cycles of recycling.