Synergistic regulation of nitrogen-vacancy-rich g-C3N4 and α-Bi2O3/β-Bi2O3 phase junction enabling dual S-scheme charge transfer for enhanced photocatalytic antibiotic degradation

The development of efficient photocatalysts for antibiotic removal remains constrained by the lack of well-defined active sites and severe charge recombination. Herein, a nitrogen-vacancy-rich carbon nitride coupled with mixed-phase bismuth oxide (α-Bi 2 O 3 /β-Bi 2 O 3 /g-C 3 N 4 -nitrogen vacancies, denoted as N V -αβBO) was rationally constructed via NaBH 4 -assisted defect engineering and in-situ phase transformation. The optimized N V -αβBO-4 shows significantly enhanced photocatalytic performance under visible light and rapidly removes tetracycline hydrochloride (TCH). Systematic characterizations show that nitrogen vacancies facilitate O 2 adsorption and activation. Meanwhile, the interfacial coupling among α-Bi 2 O 3 , β-Bi 2 O 3 and defective g-C 3 N 4 (N V -CN-10) promotes directional charge transfer and suppresses carrier recombination. More importantly, a dual S-scheme charge-transfer pathway is established. This pathway preserves photogenerated electrons and holes with strong redox capability, thereby promoting reactive oxygen species (ROS) generation. This work demonstrates a synergistic strategy by integrating defect engineering with phase-junction construction, providing new insights into the design of high-performance photocatalysts for antibiotic wastewater treatment.