Electron-trap modulated graphitic carbon nitride nanosheets for ultrafast antibiotic degradation and high-rate hydrogen evolution

• NaOH-modulated g-C 3 N 4 electronic structure with minimal structural disorder • Na-induced shallow traps suppress recombination and enhance charge-carrier dynamics. • Small Urbach energy shift supports controlled NaOH tuning of shallow tail states. • Complete removal of 20 ppm parent antibiotics within 8 min under 10 W LED. • Pt-Na(0.01)–CN shows an initial H 2 evolution rate of 8.8 mmol g −1 h −1. Graphitic carbon nitride (g-C 3 N 4 ) is a promising metal-free photocatalyst, but its efficiency is often limited by rapid charge carrier recombination. We report a scalable, one-step sodium-assisted thermal polycondensation of urea that achieves precise electronic modulation while preserving the structural integrity of the g-C 3 N 4 framework. Urbach energy analysis was employed to quantify band-tail disorder, showing a modest increase of 11.3 meV (71.4 to 82.7 meV). Together with time-resolved fluorescence spectroscopy, this indicates mild band-tail broadening and predominantly shallow electron trapping rather than the formation of a large population of detrimental deep traps. Time-resolved fluorescence spectroscopy confirms enhanced charge carrier separation, as sodium-induced shallow traps suppress radiative recombination and facilitate electron transfer to the surface. Consequently, optimized Na(0.01)–CN nanosheets exhibit exceptional dual-functionality. Under single low-energy 416 nm LED irradiation (3.4 W m −2 ), the material achieves complete degradation of parent Ofloxacin and Tetracycline (20 ppm) within just 8 min with an apparent quantum yield of 5.83 %. Furthermore, the catalyst demonstrates a remarkable initial hydrogen evolution rate of 8.8 mmol g −1 h −1 under simulated solar light. These findings highlight that maintaining low Urbach energy through controlled doping is a superior strategy for developing stable, high-performance photocatalysts for environmental remediation and solar fuel production.