Synergistic effect of photocatalysis and thermocatalysis for selective oxidation of aromatic alcohols to aromatic aldehydes using Zn3In2S6@ZnO composite

Selective oxidation of aromatic alcohols to corresponding carbonyl compounds under mild conditions has a promising prospect in industry. In the paper, we successfully prepared a new mode of photothermocatalyst, Zn3In2S6@ZnO composite, which shows dramatically enhanced activity for selective oxidation of benzyl alcohol to benzaldehyde compared with single Zn3In2S6 and ZnO under visible light illumination. The enhancement is due to a synergistic effect of low-temperature thermocatalysis on ZnO and photocatalysis on Zn3In2S6. ZnO could weaken bonds of the CHα and the OH. Then the reactive species (O2− and h+) generated on Zn3In2S6 could be easy for selective oxidation of benzyl alcohol to produce benzaldehyde. The photoelectrochemical and photoluminescence (PL) results and a series of control experiments (e.g. reaction temperature and radical scavenger) prove this synergistic effect and proposed mechanism. Moreover, the stable performance and high activity of Zn3In2S6@ZnO for other aromatic alcohols indicate its applicable potential. This study provides a promising way to combine photocatalysis and thermocatalysis for the design of novel and efficient visible-light-driven catalyst for selective oxidation of aromatic alcohols or other organics under mild reaction conditions.