Unraveling the phosphorus-nitrogen bridge in carbon quantum dots/carbon nitride for efficient photodegradation of organic contaminants

Limited transport and migration of photoinduced charges in polymeric carbon nitride (g-C3N4) within the planar layers remain a great challenge for achieving favorable photocatalysis. Herein, phosphorus-doped carbon quantum dots (PCDots) implanted intra-layer carbon nitride nanosheet (PCDots-C3N4) photocatalyst with phosphorus-nitrogen (P–N) bridging was prepared. The 13C and 31P of nuclear magnetic resonance, X-ray photoelectron spectroscopy, and density functional theory calculations confirmed the formation of a P–N bridge. Additionally, implanting PCDots enlarged the π-π conjugated electronic structure and modulated the plane structure of g-C3N4. The atomic-level connection by the P–N bridge dramatically extended the delocalization effect and facilitated the intramolecular charge transfer. PCDots-C3N4 demonstrated efficient photodegradation of tetracycline hydrochloride (TC) and bisphenol A (BPA) than both g-C3N4 and CDots-C3N4, reaching 76% and 100%, respectively. The possible degradation pathways of TC and BPA were also discussed. This work provides an efficient strategy for rapid electron transfer to form a new paradigm for wastewater remediation.