Defective engineering in graphitic carbon nitride nanosheet for efficient photocatalytic pathogenic bacteria disinfection

[Display omitted] •The porous g-C3N4 ultra-thin nanosheet with tunable nitrogen vacancy was obtained.•Nitrogen vacancy plays significant role in modulating photocatalytic properties.•The photocatalytic disinfection mechanism was deeply studied by multi technologies. In this work, porous defective g-C3N4 ultrathin nanosheets were prepared through thermal condensation of freeze-dried precursor. First-principles density functional theory (DFT) calculations well predicted the role of VN in modulating energy levels and photocatalytic properties. The optimally defective g-C3N4 manifested the better photocatalytic disinfection performance towards E. coli and S. aureus than pristine g-C3N4, respectively. The gradual damaged cell membrane for E. coli and the intimate mechanical constraint for S. aureus was imaged to further decipher the antibacterial behavior. The synergistic effect of enhanced visible light absorption ability, more exposed active sites and improved photogenerated charge separation was responsible for excellent photocatalytic disinfection activity. The photocatalytic disinfection mechanism towards E. coli was explored by electron spinning resonance (EPR), radical scavenger and spectral quantification technology, confirming the major role of h+ and O2−. This study provides alternative strategy for rational design of effective g-C3N4-based photocatalysts by defective engineering for environmental remediation.