A simple, efficient, and environmentally benign method has been developed for the synthesis of 2-substituted benzimidazole using one pot reaction of o-phenylenediamine with substituted aldehydes in good to excellent yields under mild conditions using low catalyst loading (CuSO4 as the selective catalyst) and atmospheric air as an oxidant. All synthesized compounds were evaluated for their in vitro anti bacterial activity against six microorganisms: Staphylococcus aureus (ATCC 11632), Streptococcus feacalis (clinically isolated), Bacillus cerus (MTCC 7350), Escherichia coli (ATCC 35218), Salmonella typhi (ATCC15499), and Pseudomonas aeruginosa (ATCC 23564). It was observed that all compounds exhibited good to moderate activity as compared to standard drug. The easy setup and purification procedure of this sustainable method and biological importance makes it appealing for bulk industry applications.