Chemoselective reduction of nitro and nitrile compounds using an Fe3O4-MWCNTs@PEI-Ag nanocomposite as a reusable catalyst

Multi-walled carbon nanotubes (MWNTs) were modified with carboxylic acid functional groups (MWCNTs-(COOH)(n)) prior to decoration with Fe3O4 nanoparticles. A further modification step by polyethyleneimine (PEI) resulted in Fe3O4-MWCNTs@PEI which provided a suitable platform for coordination and in situ reduction of silver ions to obtain an Fe3O4-MWCNTs@PEI-Ag nanocomposite with highly dispersed Ag nanoparticles. The Fe3O4-MWCNTs@PEI-Ag hybrid material was characterized by various techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), and was used as an efficient catalyst for chemoselective reduction of nitroaromatic and nitrile compounds to their corresponding amines in aqueous solution at ambient temperature. Nitrofurazone, a cytotoxic antibiotic, as a non-aromatic example was also reduced selectively at the nitro group without reduction of the other functionalities in the presence of Fe3O4-MWCNTs@PEI-Ag. The catalyst was magnetically recoverable and maintained its activity for at least six cycles without considerable loss of efficiency.