A photochromic composite with enhanced carrier separation for the photocatalytic activation of benzylic C–H bonds in toluene

Photocatalysis based on the use of semiconducting materials is an emerging alternative to conventional thermochemical catalysis, and it has the potential to promote chemical synthesis under greener and milder conditions. However, heterogeneous photocatalytic organic reactions are still in their infancy, limited by the low-efficiency carrier separation of the currently available photocatalytic materials. Here, we report photochromic Bi2WO6–x/amorphous BiOCl (p-BWO) nanosheets, which, distinct from pristine Bi2WO6, show blue colouration upon visible light irradiation and are bleached by atmospheric oxygen. Studies on the microscopic structure of the material reveal the existence of abundant W(vi)O6–x units, which serve as the sites for the fast and continuous consumption of photogenerated electrons, thereby effectively facilitating the separation of electron–hole pairs. The prepared composite features a remarkable enhancement in performance for the photocatalytic oxidation of toluene with a conversion rate 166-fold higher compared with that of pristine Bi2WO6. Despite its potential, the visible light-triggered photocatalytic oxidation of toluene remains difficult due to the lack of efficient and scalable catalytic strategies. Now, a photochromic Bi2WO6–x/amorphous BiOCl composite is reported with the ability to oxidize toluene into benzaldehyde and benzoic acid with outstanding rates and quantum efficiencies.