Single oxidizable moiety enables complete defluorination of per- and polyfluoroalkyl substances in heat-activated persulfate.

Despite decades of research on the degradation of polyfluoroalkyl substances (PFAS) by heat-activated peroxydisulfate (PDS), a generalizable, structure-based predictive framework has remained elusive. Herein, we propose that the susceptibility of PFAS to complete defluorination by activated PDS is mechanistically determined by the presence of a single oxidizable moiety, including carboxylate (-CO2-), alkyl (-CH or -CH2-), alkenyl (C=C), and (sulfon)amides (-CON- or -SO2N-) groups. This principle was validated using 26 PFAS representative of the dominant structures encountered in contaminated environments, with near complete defluorination within 8 h at 85 °C. The defluorination efficiency was independent of oxidizable moiety position, perfluoroalkyl chain length, or the presence of non-oxidizable substituents. Mechanistic analyses reveal moiety-specific initiation pathways and distinct roles for reactive oxidants. Notably, SO4•- is not the primary oxidant but a precursor to •OH (via reaction with H2O) and HSO4• (via protonation). Alkyl, alkenyl, and (sulfon)amide PFAS are first transformed by •OH into perfluoro(di)carboxylates before further defluorination by HSO4•, whereas HSO4• attack on -CO2- in parent PFAS and carboxylate intermediates is the rate-limiting defluorination step. This process was effective across wide concentration ranges and exhibited favorable energy consumption relative to established destructive technologies. Although ineffective for perfluoroalkyl sulfonic acids and their Cl/O derivatives, these findings establish an oxidizable-moiety framework that provides actionable guidance for broad PFAS remediation and the rational design of inherently degradable structures.