Photocatalytic Selective Oxidation of Toluene into Benzaldehyde on Mixed-Valence Vanadium Oxide V6O13 Catalyst with Density Functional Theory

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 V6O13 shows the high photocatalytic activity because of the different photocatalytic mechanism from the oxidation-reduction reaction. The catalyst V6O13 and aliphatic alcohol would form V6O13-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 V6O13 could efficiently achieve photocatalytic oxidation of toluene and there is a similar photocatalytic mechanism for toluene by catalyst V6O13. In this work, the photocatalytic selective oxidation of toluene to benzaldehyde by V6O13 catalyst is systematically investigated by density functional theory. The results show that V6O13 catalyst can effectively activate toluene C(sp(3))-H bond into benzyl with the activation energy is 14.2 kcal mol(-1). The V6O13-toluene complex has stronger light absorption in the range from 200 to 800 nm than that of the individual V6O13 clusters. Furthermore, the barrier for the dehydration of C6H5CH2OOH and C6H5CHOHOH decreased from 49.0 to 35.0 kcal mol(-1) and from 26.3 to 19.5 kcal mol(-1), respectively. We trace these surprising results to the novel photocatalytic mechanism that the V6O13-toluene complex could be excited by light to effectively activate the toluene C(sp(3))-H bond. Our work may provides new opportunities and challenges for photocatalytic field. [GRAPHICS] .