Halogen‑Engineered Nitrogen‑Doped Carbon for Dual Nonradical Peroxymonosulfate Activation in Water Purification

ABSTRACT

Peroxymonosulfate (PMS)‐based advanced oxidation processes are attractive for water purification but are often limited by short‐lived radicals that are easily quenched in complex matrices. Here we report a halogen‐modulation strategy to engineer the interfacial microenvironment of nitrogen‐doped carbon (N‐C) for robust, metal‐free PMS activation. A family of halogen‐doped carbons (NX‐C; X = F, Cl, Br, and I) is synthesized via molten‐salt‐assisted conversion of ZIF‐8, among which bromine‐doped N‐C (NBr‐C) exhibits a lattice‐strained, hierarchically porous framework with highly polarized graphitic‐N sites. NBr‐C delivers a 134‐fold enhancement in the phenol degradation rate constant ( k _obs = 2.55 min ⁻¹ ) and 70.5% total organic carbon (TOC) removal within 5 min. Mechanistic experiments combined with density functional theory (DFT) calculations reveal that Br doping steers PMS activation away from short‐lived radicals toward dual nonradical pathways: singlet oxygen ( ¹ O ₂ ) oxidation and a catalyst‐mediated direct electron‐transfer process. The NBr‐C/PMS system maintains nearly complete pollutant removal over pH 3–11, in the presence of common inorganic anions and natural organic matter, in real waters, and under continuous‐flow operation. This work establishes halogen‐regulated interfacial microenvironment engineering as a powerful principle for designing robust, metal‐free PMS activators operating through selective nonradical pathways.