Synthesis and application of Fe/Ni modified ZIF-8 as an environmentally friendly photocatalyst for methylene blue dye degradation under visible light

Abstract

A series of Fe(iii) and Ni(ii) bimetallic doped ZIF-8 materials were synthesized via a facile, green, room-temperature method to act as highly efficient photocatalysts for methylene blue (MB) degradation. The study reveals that the Fe/Ni bimetallic synergistic effect is crucial for enhancing photocatalytic performance. Optimization of the metal doping ratio revealed that Fe(15)/Ni(5)@ZIF-8 exhibited the highest photocatalytic efficiency. This optimized catalyst maintained the parent ZIF-8 crystalline structure but showed an increased particle size (80 nm). X-ray Photoelectron Spectroscopy (XPS) confirmed the successful metal incorporation and, importantly, the presence of mixed valence states for both iron (Fe2+/Fe3+) and nickel (Ni2+/Ni3+). This electronic modification leads to a significant reduction of the material's band gap to 2.26 eV, enabling strong visible light absorption. Consequently, the optimized photocatalyst exhibited outstanding activity, achieving 95.06% degradation of MB within 180 minutes under visible light, following pseudo-first-order kinetics (k = 2.73 × 10−2 min−1). This work not only presents a highly stable and effective catalyst but also underscores that harnessing bimetallic synergy is a powerful strategy for engineering advanced MOF-based materials for environmental remediation.