Interfacial Mn–N bonding engineered MnCo2S4/g‑C3N5 S-scheme heterojunctions for efficient visible‑light tetracycline degradation

Nitrogen-defect-rich DCN enables Mn–N interfacial coupling with MnCo 2 S 4 . • Interfacial Mn–N bonding and S-scheme charge transfer promote efficient charge separation. • Enhanced ROS generation is achieved in the heterojunction under visible-light irradiation. • Optimized catalyst shows high visible-light activity and stability for TC degradation. • Degradation pathways and toxicity evolution demonstrate the deep mineralization and detoxification of TC. Constructing well-defined heterointerfaces is crucial for regulating charge separation and surface reactions in photocatalysts. Herein, MnCo 2 S 4 /g‑C 3 N 5 S-scheme heterojunctions were fabricated via an in-situ growth strategy, in which defect-associated nitrogen sites in g‑C 3 N 5 act as coordination centers to anchor Mn, forming well-defined Mn–N interfacial bonds. XANES/EXAFS analyses and density functional theory calculations confirm the presence of Mn–N coordination at the interface and reveal its role in tailoring the local coordination environment and electronic configuration of Mn. The Mn–N coupled heterointerface promotes directional separation and transfer of photogenerated carriers, as evidenced by photoelectrochemical measurements, electron spin resonance and femtosecond transient absorption spectroscopy, which demonstrate accelerated charge migration and enhanced generation of reactive oxygen species. Benefiting from this interfacial Mn–N bonding-driven charge separation, the optimized MnCo 2 S 4 /g‑C 3 N 5 -II heterojunction achieves markedly improved visible-light photocatalytic activity toward tetracycline degradation, reaching ~90.8% removal within 120 min with an apparent rate constant of 0.01371 min −1 , which far surpasses the individual components. This work highlights interfacial Mn–N bonding engineering as an effective strategy for constructing robust S-scheme heterojunctions with promoted charge separation and surface redox processes. Download: Download high-res image (182KB) Download: Download full-size image