Construction of Z-Scheme ZIF67/NiMoO4 Heterojunction for Enhanced Photocatalytic Degradation of Antibiotic Pollutants

The rational design of heterojunction photocatalysts enabling fast transportation and efficient separation of photoexcited charge carriers is the key element in visible light-driven photocatalyst systems. Herein, we develop a unique Z-scheme heterojunction consisting of NiMoO₄ microflowers (NMOF) and ZIF67, referred to as ZINM (composite), for the purpose of antibiotic degradation. ZIF67 was produced by a solution process, whereas NMOF was synthesized via coprecipitation with a glycine surfactant. The NMOF exhibited a monoclinic phase with a highly oriented, interconnected sheet-like morphology. The ZINM showed better optical and charge transfer characteristics than its constituents, ZIF67 and NiMoO₄. Consequently, the developed heterojunction photocatalysts exhibited superior photocatalytic redox capability; the ZINM30 (the composite with 30 wt.% of NiMoO₄ loaded) could degrade 91.67% of tetracycline and 86.23% of norfloxacin within 120 min. This enhanced photocatalytic activity was attributable to the reduced bandgap (E_gap = 2.01 eV), unique morphology, high specific surface area (1099.89 m²/g), and intimate contact between ZIF67 and NiMoO₄, which facilitated the establishment of the Z-scheme heterojunction. Active species trapping tests verified that •O₂^- and h⁺ were the primary species, supporting the proposed degradation mechanism. This work highlights a valid Z-scheme ZIF67/NiMoO₄ heterojunction system for efficient carrier separation and, therefore, enhanced photocatalytic degradation of antibiotics.