Photocatalytic Selective Oxidation of Toluene into Benzaldehyde on Mixed-Valence Vanadium Oxide V.sub.6O.sub.13 Catalyst with Density Functional Theory

• Published in: Catalysis letters 2023-10, Vol.153 (10), p.2917
• Main Authors: Liu, Yue-Lan, Ding, Yu-Feng, Yin, Shuang-Feng, Cai, Meng-Qiu
• Format: Article
• Language: English
• Subjects: Activation energy; Aldehydes; Density functionals; Oxidation-reduction reaction; Toluene; Vanadium
• ISSN: 1011-372X
• DOI: 10.1007/s10562-022-04184-z

The photocatalytic oxidation of toluene to benzaldehyde has attracted wide attention due to its mild condition, low cost and green process. In general, the traditional semiconductor photocatalytic mechanism is an oxidation-reduction reaction between photogenerated carriers and reactants. Recently, the catalyst V.sub.6O.sub.13 shows the high photocatalytic activity because of the different photocatalytic mechanism from the oxidation-reduction reaction. The catalyst V.sub.6O.sub.13 and aliphatic alcohol would form V.sub.6O.sub.13-alkoxide, which could be excited by visible light to effectively activate the C-H bond of [alpha]-C. However, it is unknown whether the catalyst V.sub.6O.sub.13 could efficiently achieve photocatalytic oxidation of toluene and there is a similar photocatalytic mechanism for toluene by catalyst V.sub.6O.sub.13. In this work, the photocatalytic selective oxidation of toluene to benzaldehyde by V.sub.6O.sub.13 catalyst is systematically investigated by density functional theory. The results show that V.sub.6O.sub.13 catalyst can effectively activate toluene C(sp.sup.3)-H bond into benzyl with the activation energy is 14.2 kcal mol.sup.-1. The V.sub.6O.sub.13-toluene complex has stronger light absorption in the range from 200 to 800 nm than that of the individual V.sub.6O.sub.13 clusters. Furthermore, the barrier for the dehydration of C.sub.6H.sub.5CH.sub.2OOH and C.sub.6H.sub.5CHOHOH decreased from 49.0 to 35.0 kcal mol.sup.-1 and from 26.3 to 19.5 kcal mol.sup.-1, respectively. We trace these surprising results to the novel photocatalytic mechanism that the V.sub.6O.sub.13-toluene complex could be excited by light to effectively activate the toluene C(sp.sup.3)-H bond. Our work may provides new opportunities and challenges for photocatalytic field.