Fe–N coordination-driven Z-scheme tubular poly(heptazine imide)/α-Fe2O3 heterojunction to improve photocatalytic degradation of levofloxacin

Poly(heptazine imides) (PHI) salts, a crystalline carbon nitride compound, exhibit significant photocatalytic activity for levofloxacin degradation, but photogenerated charge carriers recombine rapidly. A direct Z-scheme tubular poly(heptazine imides)/hematite (PHI/α-Fe₂O₃) heterojunction is fabricated in this study, with an internal electric field (IEF) engineered to effectively inhibit photogenerated charge carrier recombination. Tubular PHI enhances electron transport, and Z-scheme heterojunction structure provides an efficient charge transfer pathway. Photogenerated electrons in the α-Fe₂O₃ conduction band migrate to the valence band of PHI under the influence of the IEF through the Fe-N coordination bond, where they recombine with holes. This mechanism effectively suppresses photogenerated charge recombination while sustaining a redox potential thermodynamically sufficient for •O₂^–/•OH formation. PHI/Fe-3 composite achieves a levofloxacin degradation rate of up to 99.13 % within 60 min in simulated sunlight, and its degradation speed can reach 7.6 times that of PHI. A synergy of theoretical calculations and experimental characterizations elucidates the charge transfer pathway and the separation mechanism of efficient charge carrier in PHI/α-Fe₂O₃. This study introduces a new approach for manufacturing PHI-based photocatalytic materials with superior photocatalytic performance.