The Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) were modified with 1,10‐ phenanthroline‐5,6‐diol and the relevant Co complex (Fe3O4@Phendiol@Co) synthesized as a nano‐magnetic heterogeneous catalyst to be used for the N‐formylation of various amines at room temperature under solvent‐free conditions. Also, in order to find the better concept of the catalyst role, the N‐formylation reaction was carried out by the use of ultrasound irradiation in the absence of the Co nano‐catalyst and the results were compared. The catalyst characterized by different methods such as the elemental analysis (CHN), ICP, FT‐IR, XRD, EDX, SEM, TEM, TG‐DTA, VSM and XPS. In addition, the antioxidant and the antibacterial activities of the Fe3O4@Phendiol@Co nano‐catalyst and its Phendiol ligand were in vitro screened by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical scavenging and disc diffusion methods. Results showed that they possess strong antioxidant activity (IC50; 0.182 ± 0.006 mg/ml) and good antibacterial potential in comparison to standards.
