Photocatalytic low-temperature defluorination of PTFE

Polytetrafluoroethylene (PTFE) is widely used owing to its exceptional chemical and thermal stability; however, these same properties render it highly persistent in the environment, contributing to long-term fluorinated waste. Conventional degradation methods, such as pyrolysis above 500 °C or treatment with alkali metals, are energy-intensive and operationally demanding, highlighting the need for mild and practical defluorination strategies for sustainable fluoropolymer recycling. Here we report a visible-light-driven photocatalytic protocol for PTFE defluorination under mild conditions. The method uses carbazole-based photocatalysts (CBZ6 and KQGZ), readily prepared in two to three steps from commercial precursors, and proceeds in standard glassware under purple light-emitting diode irradiation. Finely divided PTFE powder (~1-μm particle size, 20-mg scale) is treated with a photocatalyst, base and sacrificial reductant, with dispersion maintained by intermittent sonication. Critical parameters influencing reactivity include photocatalyst identity and loading, dispersion efficiency, base purity and physical form, light source configuration, temperature control and irradiation time. The reaction yields soluble fluoride salts and a defluorinated amorphous carbon, along with carbon-derived oxyanions. Fluoride ions are quantified by ¹⁹F NMR spectroscopy or ion chromatography and can be recovered as potassium fluoride by recrystallization. The amorphous carbon is characterized primarily by Raman spectroscopy, supported by X-ray photoelectron spectroscopy, solid-state NMR and IR spectroscopy. The protocol is straightforward and accessible to researchers with standard training in organic synthesis, including graduate students and experienced laboratory technicians. The full protocol, encompassing photocatalyst preparation, PTFE defluorination and product characterization, can be completed in 189 h (59 h hands-on time).