Anchoring single-atom Cu on tubular g-C3N4 with defect engineering for enhanced Fenton-like reactions to efficiently degrade carbamazepine: Performance and mechanism.

[Display omitted] • Tubular g-C 3 N 4 with different vacancies was prepared by temperature control. • Cu anchored in C vacancy showed lowest formation energy and shortest Cu-N bonds. • The presence of 1O 2 facilitated the effective degradation of carbamazepine. • The redox cycles of Cu(I)/Cu(II)/Cu(III) accelerated the Fenton-like reaction. • Five possible degradation pathways for carbamazepine were proposed. Efficient construction of the active site is crucial for Fenton-like reactions. In this study, tubular carbon nitride with different vacancies (V-TCN) was prepared by simple temperature control. The affinity of the nitrogen atom generated by the carbon vacancy was used to anchor single-atom Cu, which achieved the precise regulation of Cu, reduced agglomeration, and maximally exposed the active site to enhance the activation of H 2 O 2. Density functional theory calculations revealed that the single-atom Cu anchored in the C2 vacancy exhibited the lowest formation energy and the shortest Cu-N bonds. The results showed that Cu/V 550 -TCN had excellent degradation performance for the hard-to-degrade carbamazepine over a wide pH range (pH = 5–11), and singlet oxygen was the main active species during the degradation process. Additionally, the redox cycles of Cu(I)/Cu(II) and Cu(II)/Cu(III) accelerated the Fenton-like reaction. Five possible degradation pathways for carbamazepine were proposed based on liquid phase mass spectrometry analysis. This study provides a new insight into the role of surface defects in regulating the active site to promote the Fenton-like reaction for the degradation of stubborn pollutants. [ABSTRACT FROM AUTHOR]