Oxygen vacancy enhanced visible light photocatalytic selective oxidation of benzylamine over ultrathin Pd/BiOCl nanosheets

Two atomic layered BiOCl nanosheets with rich oxygen vacancies (NS-OV) were constructed via surface Pd deposition (0.5 wt%) as a multifunctional photocatalyst (Pd0.5/NS-OV), which exhibits high conversion (>95%) and precise selectivity (>98%) for benzylamine coupling to N-benzylidenebenzylamine under visible light irradiation and 1 atm air pressure. XPS and UV–vis DRS indicated that ultrathin structure of the nanosheets induces the formation of surface oxygen vacancies (OV), resulting in abundant surface low-coordinated Bi atoms and expanded visible light absorpion. Moreover, in-situ EPR results revealed that surface OV sites contribute to assemble O2 molecules from air to surface of NS-OV. Additionally, in-situ FTIR suggested that low-coordinated Bi selectively adsorb benzylamine molecules via -N···Bi- coordination bonds at the interfaces, inducing polarization and activation of -C-N bonds. Furthermore, Pd sites were observed to crucially participate in formation of active ∙O2- species under visible light irradiation. Based on multifunctional features, a possible synergistic mechanism was proposed.