<p>Zinc oxide (ZnO) is a widely studied semiconductor material recognized for its wide band gap, high exciton binding energy, and stable wurtzite crystal structure. Its non-toxic nature and industrial scalability make it highly attractive for photocatalytic applications. Doping ZnO with copper (Cu) introduces beneficial structural and surface modifications, including reduced crystallite size, increased porosity, and enhanced surface area, which together improve light absorption and charge carrier mobility. This study investigates the synthesis and photocatalytic performance of Cu-doped ZnO nanocomposites for the degradation of bromophenol blue dye, a common organic pollutant in wastewater. The incorporation of Cu was confirmed through various characterization techniques, indicating successful lattice integration and morphological transformation from rod-like to spherical nanoparticles. BET surface area analysis revealed a significant increase in surface area and pore volume compared to pure ZnO. These enhancements facilitated improved photocatalytic efficiency under light irradiation, leading to effective degradation of bromophenol blue. The results demonstrate that Cu-doped ZnO nanocomposites offer a promising, eco-friendly solution for the removal of synthetic dyes, contributing to sustainable water purification technologies.</p> Graphical abstract <p></p>