Tailoring Crystal Symmetry to Boost the Photocatalytic Degradation of Mixed Dyes and Antibiotics over Centrosymmetric BiOBr and Non-Centrosymmetric BiOBrO ₃ Nanosheets

Water pollution has become a critical global concern, with antibiotics and industrial dyes identified as major emerging contaminants. These persistent chemicals are widely distributed in aquatic environments, where they not only endanger aquatic ecosystems but also pose severe risks to human health. Their uncontrolled release and accumulation contribute to the dissemination of antibiotic residues, exacerbating ecological imbalances and heightening public health threats. In this study, Sillén-Aurivillius layered oxyhalides were synthesized via a hydrothermal route. The Centrosymmetric BiOBr and non-Centrosymmetric BiOBrO3 layered bismuth-based nanomaterials were engineered into two-dimensional and three-dimensional morphologies, respectively, resulting in a larger surface area and better photocatalytic activity. They exhibited high efficiency and stability as photocatalysts for the degradation of antibiotics, such as Ciprofloxacin and Tetracycline Hydrochloride, as well as industrial dyes in aqueous systems. Upon exposure to ultraviolet light, the BiOBr and BiOBrO3 nanostructures generate Reactive Oxygen Species (ROS), including hydroxyl radicals, with strong oxidative capability. These ROS effectively attack the molecular structures of antibiotics, promoting their transformation into simpler and less harmful compounds. Notably, the non-Centrosymmetric lattice facilitates spontaneous polarization, which enhances charge separation and accelerates the breakdown of mixed pollutants. In BiOBrO3, the trigonal pyramidal BrO3 units break inversion symmetry, generating an internal polarization field that assists the separation and transport of photogenerated electrons and holes.