Fabrication of Z-scheme UiO-66-NH ₂ /g-C ₃ N ₄ /BiVO ₄ Heterojunction for Superior Visible-Light Photocatalytic Degradation of Dyes

A ternary heterojunction UiO-66-NH₂/g-C₃N₄/BiVO₄ (UGB) was synthesized by an in situ hydrothermal approach, showing superior photocatalytic degradation of Rhodamine B (RhB), Methylene Violet (MV), and Coriacide Black MR (CBMR) under visible-light irradiation. The UGB composite exhibited the highest degradation efficiency of RhB, MV, and CBMR in comparison with pristine and binary nanocomposites. The present study proposes an effective technique for developing a ternary photocatalytic system for dye degradation. The enhanced photocatalytic activity can be attributed to its improved visible-light absorption, a large specific surface area, and the development of an efficient heterojunction driven by the Z-scheme mechanism. Using energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and X-ray diffraction (XRD), the crystal structure and chemical characteristics of the samples were assessed. Structural analysis revealed a mesoporous structure with a large surface area (9.3 m²/g) and a reduced band gap (∼2.0 eV), allowing effective light absorption and charge separation. Additionally, this catalyst exhibited stable performance throughout four consecutive reaction cycles. The Z-scheme mechanism formed at the ternary composite interface allows photoexcited charge carriers to be separated and transferred, as evidenced by the PL and EIS spectra. The trapping experiment and the process of photoinduced electron-hole pair transfer were used to further suggest the photocatalytic mechanism. These findings indicate that UGB is an effective and reusable photocatalyst for wastewater treatment.