Sustainable defluorination pathway: from perfluoro gem diol hydration to electrocatalytic removal of CF3 at room temperature

Abstract

At room temperature, the carbonyl functional group of some short-chain fluoroketones (SFKs) undergoes nucleophilic addition with water to form a perfluoro gem diol without protonation. This is due to the electron-withdrawing effect of their perfluoro functional group. By combining density functional theory (DFT) calculations with hydration experiments, the conditions for geminal diol formation at room temperature were determined: the Gibbs energy barrier of the transition state must not exceed 46.90 kcal mol⁻¹, and the endergonicity associated with the formation of the target geminal diols must remain below 8.01 kcal mol⁻¹. The strong electron-donating effect of the gem diol significantly weakens the chemical bond at the α-position. This leads to the hydrogenolysis of the CF₃ group and fluorine atoms under electrocatalytic conditions, where inexpensive zinc serves as the catalyst. This eventually produces a hydrogen-substituted product without branched chains at the α position. Additionally, the alkaline environment necessary for hydrogenolysis is gradually formed during electrocatalysis with potassium fluoride (KF). The hydrogen fluoride (HF) generated during the defluorination reaction undergoes neutralization to maintain system neutrality and prevent alkaline decomposition of the perfluorinated gem diol. The entire system is in an aqueous homogeneous environment and the reaction can proceed smoothly at room temperature. This provides a more environmentally friendly and efficient approach for the synthesis of partially fluorine-substituted organic compounds at the α position, offering a potential solution for the degradation of highly fluorinated PFAS compounds in the environment.