Construction of β-Cyclodextrin-Modified BiOIO3/β-Bi2O3Type-II Heterojunctions for Efficient Visible-Light Photocatalytic Degradation of Oxytetracycline Hydrochloride

Antibiotic residues in aquatic environments pose a persistent threat to ecosystems and human health, necessitating efficient remediation strategies. This study presents a supramolecular-engineered type-II heterojunction that integrates β-cyclodextrin (β-CD) surface functionalization with a coral-like BiOIO3/β-Bi2O3 heterostructure for enhanced visible-light photocatalytic degradation of oxytetracycline hydrochloride (OTC). β-CD functionalization simultaneously extends visible-light harvesting through supramolecular sensitization and concentrates OTC molecules at the catalyst surface via host–guest inclusion complexation, which collectively accelerates interfacial charge-transfer kinetics. Concurrently, the staggered type-II band alignment between BiOIO3 and β-Bi2O3 promotes efficient spatial separation of photogenerated carriers, suppressing recombination. The optimized composite (2.5β-CD/BiOIO3/30β-Bi2O3) achieves 87.34% OTC degradation within 60 min, exhibiting a pseudo-first-order rate constant 2.87-fold that of pristine BiOIO3. Comprehensive characterizations confirm the heterojunction architecture and reactive oxygen species evolution. The catalyst exhibits satisfactory photostability after being used 4 times. Degradation pathways are elucidated via high-performance liquid chromatography-mass spectrometry (HPLC-MS), while density functional theory (DFT) calculations of electrostatic potential, Highest Occupied Molecular Orbital (HOMO), and Lowest Unoccupied Molecular Orbital (LUMO) distributions identify the preferential reactive sites of OTC, providing molecular-level mechanistic insight. This work decouples the synergistic contributions of surface supramolecular engineering and heterojunction band engineering, offering a design strategy for photocatalytic remediation of refractory pharmaceutical pollutants.