<p>This study investigates the synthesis, characterization, and catalytic application of Fe₃O₄ nanoparticles (NPs) derived from the <i>Euphorbia milii</i> leaf extract. The nanoparticles were synthesized by reducing iron salts (FeSO₄ and FeCl₃) in the presence of the plant extract, with the formation of Fe₃O₄ confirmed through UV–visible, FTIR, and SEM analyses. The catalytic activity of Fe₃O₄ NPs was evaluated through the reduction of 4-nitrophenol (4NP) to amino phenol in the presence of sodium borohydride (NaBH₄). The reaction exhibited a high reduction in efficiency, achieving 82.63% conversion at 20 min at a 0.1 mM 4NP concentration. The reduction reached 80.36% at 0.2 mM 4NP after 24 min, highlighting the influence of substrate concentration on the reaction rate. Optimization of reaction conditions revealed that a 2.0 mM NaBH₄ concentration achieved the highest reduction, with a 90.68% conversion within 14 min. Kinetic studies indicated that the reduction followed pseudo-first-order kinetics with an apparent rate constant (<i>k</i>_app) of 0.0962 min⁻¹ and an R² value of 0.9424. The recyclability of the catalyst was also evaluated, showing that Fe₃O₄ NPs maintained 82.63% reduction efficiency in the first cycle, which decreased to 71.09% in the third cycle. These findings highlights the potential of Fe₃O₄ NPs for environmental and industrial applications, particularly in catalytic remediation of organic pollutants.</p> Graphical Abstract <p></p>