Orchestrating donor-acceptor motifs and S-scheme heterojunctions to unlock precision electron steering in CTFs/g-C3N4 for superior antibiotic degradation

Achieving efficient charge transfer and separation relies on constructing effective electron-transfer channels tailored to composite photocatalysts. Herein, an S-scheme heterojunction was constructed between g-C 3 N 4 and covalent triazine frameworks (CTFs) to establish a directional internal electric field (IEF). The effects of donor (D) chain extension and increased acceptor (A) number on intramolecular electron transport was conducted. DFT calculations and photoelectrochemical tests indicated that, with the stepwise structural evolution from A1-D-A1 (CTF-1) to A1-D-D-A1 (CTF-2) and further to A1-D-A2-D-A1 (CTF-Azo), the electron density within the CTFs framework gradually increased. When integrated into the S-scheme heterojunction, this concerted structural engineering created an electron-rich interface that efficiently channeled electrons to adsorbed oxygen, yielding a 1.89-fold enhancement in·O 2 − generation compared to g-C 3 N 4 . This rational design enabled 1 wt% CTF-Azo/g-C 3 N 4 to achieve 92% degradation of Levofloxacin (LVX) within 120 min under visible light irradiation and demonstrated a 2.61-fold improvement over g-C 3 N 4 along with deep mineralization. A plausible photocatalytic degradation pathway was proposed, and toxicity evaluation confirmed a reduced ecological risk of the generated intermediates. Moreover, 1 wt% CTF-Azo/g-C 3 N 4 demonstrated robust performance in various complex water systems, highlighting its practical potential. This work demonstrates that orchestrating D-A molecular motifs with S-scheme heterojunctions offers a powerful paradigm for precision electron steering toward efficient antibiotic photodegradation.