This work reports the catalytic activity of nitrogen-doped carbon nanotubes (N-CNT) in the reductive N-alkylation of nitro compounds. N-CNT catalyze the reductive N-methylation of nitro- and dinitrobenzenes and nitrotoluenes to the corresponding N-methyl and N,N-dimethyl amines when methanol is used as the solvent. N-CNT were synthesized via a chemical vapor deposition method using acetonitrile over a Ni/CaO catalyst. The obtained N-CNT were characterized by transmission electron microscopy, scanning electron microscopy, x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, nitrogen adsorption/desorption, thermogravimetric analysis, and Fourier-transform infrared spectroscopy. The influence of surface carboxyl functional groups and nitrogen doping of carbon nanotubes on hydrogenation and N-methylation reactions is demonstrated. The results provide the first evidence that carbon material, particularly N-CNT can serve as efficient metal-free catalyst for the one-step synthesis of secondary and tertiary aromatic amines from the corresponding nitro compounds. The demonstrated bifunctional behavior of N-CNT, which combines redox activity for nitro group reduction and acid-base functionality for N-alkylation, highlights their potential as sustainable alternatives to conventional metal-based catalysts.
Stets et al. (Wed,) studied this question.