Oxygen Vacancy-Modified TiO2/Ti3C2/CdS Nanocomposites for Photocatalytic Selective Oxidation of Amines

A TiO2/Ti3C2/CdS (TTCS) photocatalytic material with oxygen vacancies (OVs) was prepared by using a one-step solvothermal method, and it was applied for photooxidative coupling reactions involving benzylamine. Under the influence of dimethyl sulfoxide and high temperatures, most of the Ti3C2-MXene was oxidized into TiO2 nanosheets and embedded on its surface. The decomposition simultaneously generated H2S, which could react with Cd2+ to form CdS. In addition, it could reduce the thermodynamically unstable transition metal atoms on the surface of MXene, resulting in OVs in TiO2. The surface OVs not only activated the O-2 molecules adsorbed on the metal oxide photocatalyst surfaces to produce active oxygen but also formed shallow donor states that promoted photogenerated charge carrier separation. This TTCS composite achieved a high conversion of benzylamine with a relatively high selectivity of N-benzylbenzaldimine. This work not only provides ideas for synthesizing composite photocatalytic materials but also offers strategies for defect engineering regulation.