Fabrication of a ZnFe2O4@Co/Ni-MOF nanocomposite and photocatalytic degradation study of azo dyes

Abstract

This study addresses the critical issue of removing organic pollutants from water, focusing on the photocatalytic degradation of Congo red (CR) dye using a novel ZnFe₂O₄@Co–Ni metal–organic framework (MOF) nanocomposite (ZFCNM). The primary aim was to develop a photocatalyst with enhanced efficiency by combining the properties of ZnFe₂O₄ with Co/Ni-MOF, leading to a low band gap (2.89 eV) and a high surface area (723 m² g⁻¹). The ZFCNM nanocomposite, synthesized via a hydrothermal method, was characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), confirming the formation of face-centered cubic ferrite and hexagonal MOF structures. Fourier-transform infrared spectroscopy (FTIR) verified the presence of carboxyl (–COOH) groups and Fe–O bonds in the composite. Photodegradation efficiency was evaluated under varying conditions, including reaction time, pH, catalyst dosage, contaminant concentration, and light intensity. The ZFCNM photocatalyst, with an equal mass ratio of Co/Ni-MOF and ZnFe₂O₄, achieved a 98% removal efficiency of CR (75 min reaction time, pH 5, at 25 °C, and visible-light intensity of a 50 W LED lamp) significantly outperforming Co/Ni-MOF (24%) and ZnFe₂O₄ (36%) alone. The estimated quantum yield (QY) was 3.00 × 10⁻⁶ molecules per photon, and kinetic studies revealed a first-order reaction pathway with an R² value of 0.9813. These results highlight the potential of ZFCNM as an effective photocatalyst for water purification applications.