Pioneering photocatalysts: WSe2/ZIF-9 Z-scheme nanocomposites for efficient hexavalent chromium removal

[Display omitted] •Synthesized WSe2/ZIF-9 nanocomposite via a hydrothermal method.•Nanocomposite has a suitable bandgap for visible-light-driven Cr(VI) removal.•Achieved 96.4 % Cr(VI) removal, outperforming pure materials.•Optimal Cr(VI) removal at acidic pH 2.•Proposed Z-scheme mechanism supported by Mott-Schottky and TRPL analysis.•Showed stability and reusability for practical applications. Removing chromium hexavalent (Cr(VI)) from wastewater is crucial due to its severe environmental and health hazards. This study synthesized a novel Z-scheme nanocomposite of WSe2/ZIF-9 using a hydrothermal method to enhance the photocatalytic removal of Cr(VI). The synthesized nanomaterials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–visible spectroscopy for the crystal structure, morphology, and bandgap analysis, respectively. The band gap of the nanocomposite lies within the visible range, making it suitable for visible-light-driven photocatalysis. The nanomaterials ’ surface charge, charge transfer, and recombination time were investigated using zeta potential measurements, electrochemical impedance spectroscopy (EIS), and time-resolved photoluminescence (TRPL) studies. The comparative photocatalytic experiments demonstrated that the WSe2/ZIF-9 nanocomposite was significantly more effective (96.4 % efficiency) in removing Cr(VI) than pure materials. The effect of pH on the photocatalytic degradation process was also studied, revealing that acidic conditions (pH 2) favored the photocatalytic removal of chromium. The Z-scheme mechanism of the WSe2/ZIF-9 nanocomposite was proposed based on Mott-Schottky analysis and supported by scavenger experiments and TRPL measurements. Furthermore, the reusability of the WSe2/ZIF-9 nanocomposite was tested and confirmed, indicating its potential for practical environmental applications. This study provides new insights into the design of efficient photocatalysts for removing toxic heavy metals from aqueous environments.