Precise thermal regulation of defect and coordination structures in carbon nitride govern divergent photocatalytic activities

Graphitic carbon nitride prepared through supramolecular prepolymerization and molten-salt strategies has shown strong potential in photocatalytic hydrogen evolution and pollutant degradation. In this work, we integrate these two approaches to construct single-atom-anchored carbon nitride (NaK-CN) and demonstrate that precise calcination temperature control enables divergent photocatalytic functionalities. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption near-edge structure (XANES) analyses were employed to elucidate the structural features of the materials. The results reveal that temperature-dependent tuning of defect concentration, coordination environment, and crystallinity effectively regulates charge separation behavior and reaction pathways. Consequently, NaK-CN-500 achieves a high hydrogen evolution rate of 12.81 mmol h −1  g −1 catalyst , while NaK-CN-550 delivers a markedly enhanced apparent rate constant of 0.431 min −1 for enoxacin degradation. This study supplements a versatile synthesis platform for tailoring carbon nitride frameworks and provides mechanistic insight for designing CN-based photocatalysts optimized for energy conversion and environmental remediation.