Facile reduction of nitrophenols: Comparative catalytic efficiency of MFe2O4 (M = Ni, Cu, Zn) nano ferrites

Nano ferrites of the formula MFe2O4 (M = Ni, Cu, Zn), synthesized using sol–gel technique, were employed to catalyze the reductive transformation of nitrophenols to aminophenols. The catalytic reduction was carried out in the excess of NaBH4 as reducing agent in aqueous medium at room temperature. CuFe2O4 and NiFe2O4 were found to be active for the reduction of nitrophenols with significant difference in their activities whereas ZnFe2O4 was found to be inactive. The kinetics of the reduction of nitrophenols to aminophenols was also investigated. The reaction followed pseudo first order kinetics. The first order rate constant values for 30 mol% of CuFe2O4 and NiFe2O4 for the reduction of 2-nitrophenol were observed to be 3.68 min−1 and 0.33 min−1 respectively. The rates of reduction for the three isomers of nitrophenol were also studied and were observed to follow the order – 2-nitrophenol > 4-nitrophenol > 3-nitrophenol. The selective formation of aminophenol was confirmed using LC-MS, 1H NMR and FT-IR spectroscopic techniques.