Heterogeneous photocatalysts proffer a promising method to actualize eco-friendly and green organic transformations. Herein, a new photochemical-based methodology is disclosed in the preparation of a wide range of benzimidazoles through condensation of o-phenylenediamine with benzyl alcohols in the air under the illumination of an HP mercury lamp in the absence of any oxidizing species catalyzed by a new photocatalyst W-ZnO@NH2-CBB. In this photocatalyst, coomassie brilliant blue (CBB) is heterogenized onto W-ZnO@NH2 to improve the surface characteristics at the molecular level and enhance the photocatalytic activity of both W-ZnO@NH2 and CBB fragments. This unprecedented heterogeneous nanocatalyst is also identified by means of XRD, FT-IR, EDS, TGA-DTG, and SEM. The impact of some influencing parameters on the synthesis route and effects on the catalytic efficacy of W-ZnO@NH2-CBB are also assessed. The appropriate products are attained for both the electron-withdrawing and electron-donating substituents in the utilized aromatic alcohols. Furthermore, preparation of benzimidazoles is demonstrated to occur mainly via a radical mechanism, which shows that reactive species such as ·O2 -, OH˙ and h+ would be involved in the photocatalytic process. Stability and reusability studies also warrant good reproducibility of the nanophotocatalyst for at least five runs. Eventually, a hot filtration test proved that the nanohybrid photocatalyst is stable in the reaction medium. Using an inexpensive catalyst, UV-vis light energy and air, as a low cost and plentiful oxidant, puts this methodology in the green chemistry domain and energy-saving organic synthesis strategies. Finally, the anticancer activity of W-ZnO nanoparticles is investigated on MCF7 breast cancer cells by MTT assay. This experiment reveals that the mentioned nanoparticles have significant cytotoxicity towards the selected cell line.
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