Room temperature complete reduction of nitroarenes over a novel Cu/SiO2@NiFe2O4 nano-catalyst in an aqueous medium – a kinetic and mechanistic study

Abstract

The current investigation reports the preparation of a novel system, Cu/SiO₂@NiFe₂O₄, as characterised by XRD, XPS, IR, SEM-EDS, TEM, ICP-AES and VSM data. Its catalytic activity was explored in nitroarene reduction using 4-nitrophenol as the model substrate for studying the reaction kinetics. The studies revealed the rate constant of the reaction at room temperature to be 0.325 min⁻¹. Each test reaction here contained only 10.6 μg of copper, wherein the activity factor was 0.511 s⁻¹ mg⁻¹, which is by far the highest for any non-noble metal catalyst reported for this reaction. Moreover, the energy of activation of the reaction was found to be 30.4 kJ mol⁻¹, which falls in the lower range of the average E_act reported in the literature for the reaction under study. Further insights on the reaction pathway indicated that the reaction followed a direct route for nitro-reduction via the formation of a nitroso derivative. Overall, we present herein an economical, efficient and environmentally benign methodology for nitroarene reduction using the designed catalyst.