Overcoming dissolved oxygen dependency in photocatalysis via hole-dominated oxidation: An ordered-disordered carbon nitride interface strategy for sulfonamides degradation in hypoxic water

Reactive oxygen species (ROS), particularly superoxide radicals (•O₂⁻) and singlet oxygen (¹O₂), are widely recognized as key intermediates in carbon nitride (CN)-based photocatalysis for environmental remediation. However, the generation of ROS in such systems is inherently constrained by the limited availability of dissolved oxygen in oxygen-depleted aquatic environments. To address this limitation, we developed an ordered-disordered CN interface composite (HCCN) by incorporating defect-rich amorphous hydrothermal carbonation carbon derived from lignin (HTCC-L) into polymeric CN, enabling efficient oxygen-independent, hole-dominated photocatalytic degradation of sulfonamides (SAs). The HCCN composite markedly promotes exciton dissociation and charge carrier migration under visible light irradiation, achieving a hole migration efficiency of 59.5%, compared to 33.3% for pristine CN. Meanwhile, the intrinsic defects introduced by HTCC-L act as electron traps that effectively suppress electron-hole recombination, facilitating the accumulation of long-lived photogenerated holes at surface reactive sites. Furthermore, HCCN exhibits enhanced adsorption affinity toward SAs, enriching target pollutants at the hole-accumulated surface and thereby boosting direct hole-mediated oxidation. The system demonstrates synergistic adsorption-photocatalytic performance for SAs with different heterocyclic substituents, maintaining high degradation efficiency even under hypoxic conditions, while showing strong resistance to coexisting inorganic anions. This study overcomes the inherent dependency of conventional photocatalysis on dissolved oxygen and presents a promising strategy for the remediation of recalcitrant organic pollutants in complex natural water bodies.