A novel magnetic core-shell nanocomposite Fe 3 O 4 @chitosan@ZnO for the green synthesis of 2-benzimidazoles

Abstract

A novel magnetic core-shell nanocomposite Fe₃O₄@Chitosan@ZnO was successfully prepared by in situ chemical precipitation method. It has a clear core-shell structure with magnetic Fe₃O₄ (about 160 nm in diameter) as core, chitosan as the inner shell, and ZnO as the outer shell, as demonstrated by the transmission electron microscopy and the related elemental mapping. Moreover, this nanocomposite has high magnetization (43.6 emu g⁻¹) so that it can be easily separated from the reaction mixture within 4 s by an external magnetic field. The introduction of the natural chitosan shell, instead of the conventional SiO₂ shell, and its combination with the active ZnO ensures this novel nanocomposite green character and good catalytic performance in the synthesis of 2-benzimidazoles with moderate to excellent isolated yields at room temperature. Notably, it can be recycled seven times without appreciable loss of its initial catalytic activity, demonstrating its good stability and making it an attractive candidate for the green synthesis of 2-benzimidazoles.

Graphical abstract