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 O2 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.