Bismuth-Based Oxyfluorides as Emergent Photocatalysts: A Review

Bismuth-based oxyfluorides (BiO_xF_3-2x) have recently emerged as promising photocatalysts due to their unique electronic structures and tunable physicochemical properties. This review provides a comprehensive overview of these materials, focusing on their crystal structures, band gap characteristics, and photocatalytic performance. Particular attention is given to BiOF, Bi₇O₅F₁₁, and β-BiO_xF_3-2x, highlighting the influence of fluorine's high electronegativity and internal electric fields on charge separation and light absorption. The potential of Aurivillius-type oxyfluorides is also discussed. Structural modifications, such as the introduction of oxygen vacancies, morphology control, and metal/non-metal doping, are examined for their effects on photocatalytic efficiency. Furthermore, various synthesis techniques and heterojunction engineering strategies involving semiconductors, carbon-based materials, and metal nanoparticles are explored to improve light harvesting and reduce charge recombination. Applications in pollutant degradation and CO₂ photoconversion are reviewed, demonstrating the versatility of these materials. Despite their promise, the challenges associated with phase identification and composition control are also emphasized, underlining the need for rigorous structural characterization. Future directions for optimizing the photocatalytic activity of bismuth-based oxyfluorides are outlined, focusing on strategies to enhance their performance.