Recently, Prof. Mingxue Li and Qiuxia Han in Henan Key Laboratory of Polyoxometalate Chemistry, the College of Chemistry and Chemical Engineering, Henan University, published a work of the application of hybrid polyoxometalate in photocatalysis that was entitled: “Special-selective C–H oxidation of toluene to benzaldehyde by a hybrid polyoxometalate photocatalyst including a rare [P₆W₄₈Fe₆O₁₈₀]^30– anion” in Journal of Catalysis.

Selective oxidation of primary carbon-hydrogen bonds under mild condition is a major challenge in academic and industrial aspects. In this work, a rare hybrid K₆(H₂O)₈H₂₄(C₂₆H₁₆N₄O₄)₈[P₆W₄₈Fe₆O₁₈₀]·6H₂O (FeW–DPNDI) was prepared from K₁₂[α-H₂P₂W₁₂O₄₈]·24H₂O, DPNDI and FeSO₄·7H₂O by solvothermal method (Figure 1). In FeW–DPNDI, [P₆W₄₈Fe₆O₁₈₀]^30– and DPNDI are orderly arranged in the three-dimensional framework by the anion···π interaction and C–H···O hydrogen bonds, that is beneficial to promote the electron transfer among components. This is not only the first example of the trimmer of Fe-substituted Dawson derivatives but also an unprecedented report on activating C-H bond of toluene by hybrid POM under white light irradiation. In contrast to the previous photocatalysts for toluene oxidation to benzaldehyde, FeW–DPNDI shows a higher selectivity. Moreover, FeW–DPNDI can be easily isolated from the products and reused at least five times with no significant change in conversion and selectivity. The mechanism of the photocatalystic reaction was also explored. This work might show one method for synthesis metal-oxo clusters for photocatalytic hydrocarbon conversion.

Figure 1. Design concept for achieving the photocatalyst for selective oxidation toluene.

Ph.D student Jie Li is the first author of this paper. Mingxue Li and Qiuxia Han are the co-corresponding authors.

This research was funded by the National Natural Science Foundation of China (21671055, 21601048), Henan University Firstclass Discipline Cultivation Project (2020YLZDYJ06, 2019YLZDJL10), the Key Scientific Research Project of Henan Higher Education Institutions (20ZX006) and Excellent Youth Foundation of Henan Province.

DOI：http://doi.org/10.1016/j.jcat.2020.10.013