Photocatalytic Defluorination of Perfluorooctanoic Acid by Twisted Linear Polymer Radicals

The exceptional persistence of per- and polyfluoroalkyl substances (PFAS) rooted in inert C-F bonds demands remediation strategies beyond energy-intensive treatments. Here, we report a bithiophene-fluorene-pyridine (BT-Fl-Py) linear polymer that achieves quantitative defluorination of perfluorooctanoic acid (PFOA) under visible-light irradiation. Upon photoexcitation, the polymer undergoes configurational torsional relaxation of the fluorene π-bridge, forming a stable twisted intramolecular charge-transfer state (TICT₁) that stabilizes photogenerated electrons in a long-lived reducing state. Concurrently, the hydrophobic polymer backbone enriches PFOA, activating C-F bonds and facilitating efficient interfacial electron transfer. The cooperation between conformationally regulated charge separation and interfacial substrate enrichment enables complete PFOA defluorination under mild conditions, establishing a sustainable route for degrading ultrastable PFAS and providing a molecular design principle for developing reducing polymer photocatalysts.