Construction of a Novel TiO₂-Covalent-Organic-Framework Heterojunction for Highly Selective Photo-Oxidation Coupling of Amines under Visible Light Irradiation

A novel heterojunction material constructed with titanium dioxide nanoparticles and covalent organic frameworks, TiO2@COF-5 NPs, was designed and synthesized successfully from HHTP, PBBA and TiO2 under solvothermal conditions. Notably, the TiO2@COF-5 heterojunction demonstrated excellent photocatalytic performance for the aerobic oxidative coupling reaction of benzylamines to N-benzyl-1-phenyl methanimines under visible light irradiation, and both high conversions (up to 99 %) and high selectivity (99 %) were achieved for various benzylamines. The ameliorated photocatalytic performance might owe much to establishing the systematic coupling between the TiO2 nanoparticles and covalent organic frameworks, which could effectively extend the wavelength range of visible light absorption and increase more reactive active sites. This study might provide a versatile approach to combining covalent organic frameworks with inorganic semiconductors to give full play to the synergistic effect of catalysis.