Boosting the elimination of bacteria via a metal-free LED/visible-light photocatalytic–antibiotic strategy

Microbial pollutants continue to threaten aquatic environments and human health, creating an increasing demand for efficient, sustainable, and innovative antibacterial technologies. Metal-free photocatalysts offer a safer and more sustainable route for water disinfection; however, their potential interactions with antibiotics remain insufficiently understood. Here, graphitic carbon nitride (g-C 3 N 4 ) photocatalysts were synthesized via melamine polymerization under controlled CO 2 -atmospheres to tailor their surface and optical properties. Four variants (CN-Air, CN-LF, CN-MF, and CN-HF) were obtained and systematically characterized. CN-LF, produced under low CO 2 flow, exhibited the highest surface area, enhanced visible-light absorption, and superior photocatalytic performance. Its antibacterial interaction with eight widely used antibiotics (gentamicin, amoxicillin, ampicillin, amoxiclav, azithromycin, cefuroxime, ceftriaxone, and tetracycline) was quantified using checkerboard assays (FICI) and inhibition-zone enhancement tests. CN-LF exhibited borderline synergistic interactions with ampicillin and cefuroxime (FICI = 0.5, at the synergy threshold), corresponding to 40% and 200% increases in antibacterial activity, respectively. Overall, these findings demonstrate that CO 2 -engineered g-C 3 N 4 provides a sustainable, metal-free platform to enhance antibiotic performance via a light-associated cooperative mechanism, suggesting a potential strategy for improving antibacterial performance and contributing to environmental safety.