<p>This study demonstrated the successful preparation of bismuth oxide (Bi₂O₂ NPs) using the co-precipitation method. XRD results demonstrated the formation of a pure and stable crystalline phase with an average crystallite size of 21.17&#xa0;nm this increases the effective surface area for photochemical reactions, while SEM images revealed a quasi-spherical morphology with an average particle size of about 64&#xa0;nm, which is favorable for increasing the effective surface area. FTIR spectra supported the presence of Bi–O and Bi–O–Bi bonds and the appearance of active surface hydroxyl groups, which enhance the chances of forming active radicals during the photocatalytic reaction. The optical properties also showed an energy band gap (≈ 2.75&#xa0;eV) consistent with that reported in the literature, making Bi₂O₂ a promising candidate for photocatalysis. Photocatalytic tests using methylene blue dye showed an initial sharp decrease in absorption due to rapid absorption on the catalyst surface, followed by gradual photolysis due to the formation of electron and hole pairs and the production of reactive oxygen species. This demonstrated the catalyst’s excellent ability to remove organic pollutants under visible light, with consistent efficiency across multiple cycles, indicating its robustness and sustainability. These results highlight the potential of Bi₂O₃ nanoparticles as effective and promising catalysts for environmental applications and pollutant treatment.</p> Graphical Abstract <p></p>