Catalytic Activity of Cu-MOF Catalyst for 4-Nitrophenol Reduction

Nitroaromatic compounds are widely used in various industries, including dye manufacturing, leather processing, plastics, fungicides, pesticides, insecticides, pharmaceuticals, and paper production. However, specific nitrophenols such as para-nitrophenol are recognized as hazardous environmental pollutants. Therefore, their removal or conversion into less harmful compounds, such as 4-aminophenol is of paramount importance. In this study, a copper-based metal-organic framework (Cu-BDC MOF) was synthesized via a simple, cost-effective hydrothermal method at different deposition temperatures. The synthesized materials were characterized using techniques such as X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The Cu-BDC MOF, which exhibited a square plate-like morphology served as an efficient catalyst for the reduction of 4-nitrophenol to 4-aminophenol. Sodium borohydride (NaBH₄) was employed as the reducing agent in conjunction with the Cu-MOF catalyst. An increase in the concentration of NaBH₄ enhanced the catalytic performance by supplying more BH₄^- ions, which act as electron donors in the reduction reaction. The 4-NP reduction reaction follows a Langmuir-Hinshelwood mechanism and demonstrates apparent pseudo-first-order kinetics, indicating the reaction proceeds via adsorption of both reactants on the catalyst surface followed by surface-mediated electron transfer.