Magnetically recyclable nano-sized Fe3O4@TiO2 heterogeneous photocatalyst for 2-substituted benzimidazoles synthesis under visible light.

• The different nano-sized Fe 3 O 4 was prepared orange oil was used as a protective agent and the different surfactants was used as a dispersant by co-precipitation method. • The nano-sized Fe 3 O 4 @TiO 2 was prepared using HNO 3 as a hydrolysis inhibitor by sol-gel method under the optimal reaction condition. • 17 target products were synthesized using Fe 3 O 4 @TiO 2 as a photocatalyst in a 15 W incandescent lamp radiation under the optimum reaction condition. Also, the photocatalysis mechanism was studied by the aid of the action of different scavengers. • The effect of substituents on reaction time has been found to have good catalytic performance for substituents with smaller steric hindrance. • The recyclability of catalysts have been studied, and it was found that Fe 3 O 4 @TiO 2 had good catalytic activity, reusability and easy separation performance in the synthesis of 2-substituted benzimidazole. The method for immobilizing TiO 2 nanoparticles on Fe 3 O 4 was presented. On the base of microscopic and spectroscopic characterizations, the prepared Fe 3 O 4 @TiO 2 nanoparticle composites were employed as a heterogeneous photocatalyst to catalyze the synthesis of 2-substituted benzimidazoles under incandescent light. The composite material exhibited the enhanced photoactivity compared to bare TiO 2 and Fe 3 O 4 , being able to yield a variety of 2-substituted benzimidazoles in moderate to good yield with recyclability and stability. A possible photocatalysis mechanism was investigated based on the free radical scavengers tracking method. It was evident that holes, ·OH radical and singlet oxygen played the important roles in the synthesis of 2-substituted benzimidazole. Fe 3 O 4 @TiO 2 was prepared and applied to the photocatalytic synthesis of 2-substituted benzimidazole compounds. [Display omitted] [ABSTRACT FROM AUTHOR]