Visible light driven selective oxidation of amines to imines with BiOCl: Does oxygen vacancy concentration matter?

The relationship between oxygen vacancy (OV) concentration of semiconductors and their photocatalytic performances is far from clarified. In this study, by tuning the OV concentration of BiOCl (001) surface via a novel H2O2 treatment coupled infrared irradiation method, we demonstrate that OV concentration of BiOCl (001) surface strongly determine its surface atomic and electronic structures to modulate the photocatalytic pathways. Being of shorter BiBi and BiO bond lengths as well as more electrons being less localized, BiOCl (001) surface with higher OV concentration favored molecular oxygen activation to generate O22− via a two-electron transfer pathway, while the generated O22− could prevent the over oxidation of amines and thus achieve high selectivity in the oxidation of amines to imines. Similar phenomena were also observed for other semiconductor photocatalysts such as TiO2 and Nb2O5, suggesting the generality of oxygen vacancy concentration mediated selectivity enhancement. These findings shed light on the relationship between the oxygen vacancy concentration and the surface structure of semiconductor photocatalysts and offer a novel pathway to realize photocatalytic selective oxidation of amines to imines.