Surface hydrogen bonds assisted meso-porous WO3 photocatalysts for high selective oxidation of benzylalcohol to benzylaldehyde

- Fm-WO3 achieved high selectivity(∼99%) and conversion(∼57%).
- Photo-generated holes oxidized benzyalcohol indirectly through OH.
- Multi-electron reduction of O2 to H2O2 further oxidized benzyalcohol.
- Suitable oxidation ability of reactive species depressed the peroxidation.

Selective photo-oxidation of alcohols displays high potential in solar energy conversion and reducing environmental pollution, yet its selectivity and conversion in aqueous phase is still far from expectation. Here we report a fluorinated meso-porous WO3 photocatalyst (Fm-WO3) exhibits significant selectivity (∼99%) and conversion (∼57%) in transforming benzylalcohol to benzaldehyde in the aqueous solution under the simulated sunlight irradiation. This high reactivity is attributed to the synergistic effect between meso-porous nanostructure and surface fluorination, where meso-porous structure supplies active sites to promote the multi-electron reduction of O2 and the surface fluorination assists the transmission of photogenerated holes. First-principles calculations further suggest that surface fluorination brings in an unoccupied impurity state in the band structure of WO3, which exhibits a strong correlation with the hydroxyl group of benzyalcohol and thus bridges the interaction between surfaces and alcohols. Meanwhile, the fluorination promotes the generation of OH by holes which can be considered as another way to oxidize benzyalcohol. Finally, a generalized reaction mechanism for selective photo-oxidation has been proposed.

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