<p>The development of efficient and sustainable photocatalysts is vital for the effective remediation of persistent organic and pharmaceutical contaminants in wastewater systems. In this study, we report the synergistic impacts of lanthanum and copper (La/Cu) co-doping, along with the incorporation of graphitic carbon nitride (g-C₃N₄), in enhancing the physicochemical properties of pristine BiFeO₃ (BFO) perovskite. Pure BFO and La/Cu co-doped Bi₁₋ₓLaₓFe₁₋_yCu_yO₃ (BLFCO) perovskites were synthesised via a simple hydrothermal method, while the BLFCO/g-C₃N₄ hybrid nanocomposite was fabricated using an ultrasonication-assisted approach. Structural characterisation through XRD, Raman, and FTIR analyses confirmed the successful incorporation of La/Cu metallic cations and the incorporation of the g-C₃N₄ matrix within the perovskite framework. Morphological investigations revealed that the g-C₃N₄ matrix interacted effectively with and stabilised the co-doped BLFCO, resulting in the formation of larger spherical and elongated aggregates. This interaction promoted the development of a well-defined porous structure, broadened particle size distribution, and increased the exposed surface area, with particle sizes ranging from 20 to 40 nm. Moreover, the BLFCO/g-C₃N₄ nanocomposite exhibited a significantly enhanced BET surface area (111.21 m²/g), increased electrical conductivity, and improved optical absorption with reduced band gap energy (1.97 eV). These enhancements were accredited to the combined effects of La/Cu co-doping and g-C₃N₄ incorporation, collectively contributing to superior charge transport and light-harvesting capabilities. The photocatalytic performance of the synthesised materials was assessed by the degradation of crystal violet (CV) dye and moxifloxacin (MOF) antibiotic under visible-light irradiation. Compared with pristine BFO and La/Cu co-doped BLFCO, the BLFCO/g-C₃N₄ heterojunction nanocomposite exhibited significantly higher degradation efficiencies, achieving 96.88% and 98.26% removal of CV and MOF with 0.01654 and 0.01687 min⁻¹ of rate constants, respectively, within 60 minutes. This exceptional photocatalytic activity was ascribed to the combined improvements in surface area, electrical conductivity, porosity, optical absorption, and the construction of an effective Z-scheme heterojunction, which together facilitated active charge carrier’s separation. In addition, the heterojunction photocatalyst revealed outstanding stability and reusability, with only a 2.8% decline in degradation efficiency after 5 multiple cycles. These findings underscore its potential as a durable and efficient photocatalyst for the remediation of hazardous organic pharmaceutical contaminants in wastewater systems.</p><p></p>