<p>TiO₂ nanomaterials are widely valued for their stability, non-toxicity, and strong photocatalytic potential in environmental applications. This study investigates the effect of codoping on the structural and photocatalytic properties of TiO₂ nanoparticles by using singly doped samples as a reference for comparison. The nanoparticles were synthesized via the sol–gel method and characterized using X-ray diffraction (XRD), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy to evaluate their structural and optical behavior. Photocatalytic activity was assessed through the degradation of methylene blue (MB) in aqueous media, revealing that incorporating dopants notably improved pollutant degradation efficiency. UV–visible spectroscopy confirmed a red shift in the absorption edge, particularly pronounced in Zn and Zn/N codoped samples, indicating enhanced responsiveness to visible light. Zn and N codoping not only modifies the electronic structure of TiO₂ but also improves the density of active surface sites, thereby promoting the adsorption and subsequent transformation of reactants under visible light irradiation. Among the samples, the Zn/N codoped TiO₂ with the highest nitrogen content exhibited superior photocatalytic performance, achieving a 99% degradation rate of MB under visible light. These results highlight the critical role of synergistic dopant interactions in modifying both the bulk electronic structure and surface chemistry of TiO₂, resulting in enhanced charge carrier separation and improved photocatalytic efficiency. This work presents a viable strategy for visible-light-driven pollutant degradation, highlighting the potential of codoping approaches for designing high-performance TiO₂-based photocatalysts. Further investigation into dopant combinations and their mechanisms may open new pathways for optimizing TiO₂ photocatalysis in environmental remediation applications.</p> Graphical Abstract <p></p>