TiO2 nanoparticles decorated with Co-Schiff base-g-C3N4 as an efficient photocatalyst for one-pot visible light-assisted synthesis of benzimidazoles.

In this study, a novel heterogeneous visible light-driven nanocatalyst was produced via the complexation of Co(ii) with g-C3N4-imine-functionalized TiO2 nanoparticles. It was characterized using different techniques such as Fourier-transform infrared (FT-IR), energy-dispersive X-ray spectrum (EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), thermogravimetric analysis (TGA), ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The catalyst promoted several different transformations in a one-pot reaction sequence: aerobic photooxidation of benzylic alcohols to aldehydes and then the tandem synthesis of benzimidazoles through the dehydrogenative coupling of primary benzylic alcohols and aromatic diamines. The photocatalyst proved to be highly active, robust, selective, and recyclable under organic reaction conditions and provided affordable products with good to high yields. The results proposed that the improved photoactivity predominantly benefits from the synergistic effects of the heterojunction of Co-carbon nitride on TiO2 nanoparticles. Moreover, this protocol provides standard conditions avoiding undesirable additives and limitations of oxidation methods, and may help to develop a new strategy for the development of photocatalysis based organic transformations.