Peroxymonosulfate activation by boron doped C3N5 metal-free materials with n → π electronic transitions for tetracycline degradation under visible light: Insights into the generation of reactive species

[Display omitted] •Boron doped C3N5 metal-free photocatalyst as efficient PMS activator was synthesized.•BCN featured n → π* electronic transitions and a narrow band gap.•h+, SO4−•, •OH and 1O2 were the main active species in 3BCN/PMS/vis system.•Continuous operation test verified the stability and high-efficiency of 3BCN.•DFT calculation results elucidated the origins of reactive species. Heterogeneous photocatalysis coupled with peroxymonosulfate (PMS) activation is regarded as an advanced water treatment technology for emerging contaminates degradation. We introduce a novel coupling system that integrates PMS with metal-free visible light-driven photocatalysis, utilizing boron doped C3N5 (BCNs), with the objective of swiftly eliminating tetracycline (TC) from wastewater. With commendable traits including a robust response to visible light, n → π* electronic transitions and a narrow bandgap, 3BCN optimized from BCNs, exhibited superior catalytic activity in photocatalysis and PMS activation. In 3BCN/PMS/vis system, the degradation efficiency of TC reached 88.6 % in 120 min, with an observed rate constant (kobs) of 0.0222 min−1 for TC removal. Moreover, in real water matrices including tap water, landscape water and secondary effluent, the 3BCN/PMS/vis system consistently maintained high and stable pollutant removal efficiency. To elucidate the underlying mechanisms, the origins of reactive species (h+, SO4−•, •OH and 1O2) were identified and the enhanced pathways in the PMS-based photocatalytic system were systematically investigated. Based on theoretical calculations, generation pathway of reactive oxygen species involving PMS oxidation and reduction over the region of boron atom neighboring N in BCN was unraveled. The BCN catalyst was employed in a flow-through device to explore its potential in practical application. The results showed that continuous and impressive efficient removal of TC was achieved with over 93 % removal rate during 32 h operation. Our findings underscore the substantial promise of chemical-photocatalysis synergy for environment remediation, offering a feasible approach to optimize the performance of metal-free materials in photo-catalytic oxidation of antibiotics.