High‐Quantum‐Yield Carbon Nitride Quantum Dots via Water Vapor Intercalation‐Exfoliation for Efficient Tetracycline Hydrochloride Degradation

Graphitic carbon nitride (g-C₃N₄) has demonstrated potential applications in addressing energy shortages and preserving water ecosystem stability due to its high efficiency in degrading antibiotics. However, the mediocre catalytic performance of bulk g-C₃N₄ is attributed to inefficient carrier transport and a high complexation rate of photogenerated electron-hole pairs. Herein, a method for fabricating carbon nitride quantum dots (CNQDs) via water vapor intercalation-exfoliation during high-temperature thermo-polymerization of g-C₃N₄ is proposed. The resulting CNQDs exhibit a high quantum yield (49.8%), reduced bandgap, and pH-dependent properties. Structural nitrogen defects and doping of oxygen-containing functional groups contribute to improved charge-transfer efficiency and enhanced photooxidation capacity of CNQDs from water vapor intercalation-exfoliation. Remarkably, the optimal CNQDs-650 demonstrates excellent photodegradation activity of tetracycline hydrochloride (TCH), ≈2.7 times higher than that of g-C₃N₄. Additionally, the photo degradation pathways of TCH are proposed based on identified intermediates. This study introduces a new and efficient approach to synthesizing CNQDs with high photocatalytic performance.