One-step synthesis of porous chlorine-modified graphitic carbon nitrides for efficient photocatalytic degradation of bisphenol A: DFT insights and mechanistic pathways under visible light

Bisphenol A (BPA), a widely used industrial chemical, poses significant environmental and health risks due its endocrine-disrupting properties and persistence in aquatic systems. This study reports the development of a porous chlorine-modified carbon nitride (CNM-Cl) photocatalyst synthesized via a one-step thermal condensation method for efficient degradation of BPA under visible light irradiation (λ > 420 nm). Among the investigated precursor ratios, the NH₄Cl/melamine ratio of 1.0 yielded the optimal CNM-Cl, achieving complete BPA removal within 1 h and exhibiting over threefold improvement in photocatalytic activity compared with pristine CNM. The enhanced performance was attributed to the increased surface area, extended visible light absorption, and improved photocarrier separation. Systematic evaluations under varying operational and environmental conditions demonstrated the robust activity and selectivity of CNM-Cl, with radical quenching experiments identifying superoxide radicals (•O₂⁻) and singlet oxygen (¹O₂) as dominant reactive species. Interestingly, humic acid promoted BPA degradation at higher concentrations, whereas anions such as Cl⁻ and HCO₃⁻ inhibited photocatalytic reactivity. Density functional theory (DFT) calculations revealed that Cl doping induces orbital redistribution and localized electrostatic potential (ESP) asymmetry without significantly altering the bandgap, thereby enhancing charge separation and surface reactivity. CNM-Cl maintained its activity over four cycles and effectively eliminated BPA’s estrogenic activity. This integrated experimental−theoretical approach offers a scalable strategy for designing high-performance photocatalysts for environmental remediation.