Interfacial Anion-Induced\nDispersion of Active Species\nfor Efficient Electrochemical Baeyer–Villiger Oxidation

Degradable polymers are an effective solution for white\nplastic\npollution. Polycaprolactone is a type of degradable plastic with desirable\nmechanical and biocompatible properties, and its monomer, ε-caprolactone\n(ε-CL), is often synthesized by Baeyer–Villiger (B–V)\noxidation that demands peroxyacids with low safety and low atom-efficiency.\nHerein, we devised an electrochemical B–V oxidation system\nsimply driven by H<sub>2</sub>O<sub>2</sub> for the efficient production\nof ε-CL. This system involves two steps with the direct oxidation\nof H<sub>2</sub>O<sub>2</sub> into •OOH radicals at the electrode\nsurface and the indirect oxidation of cyclohexanone by the generated\nreactive oxygen species. The modulation of the interfacial ionic environment\nby amphipathic sulfonimide anions [e.g., bis(trifluoromethane)sulfonimide\n(TFSI<sup>–</sup>)] is highly critical. It enables the efficient\nB–V oxidation into ε-caprolactone with ∼100% selectivity\nand 68.4% yield at a potential of 1.28 V vs RHE, much lower than the\npotentials applied for electrochemical B–V oxidation systems\nusing water as the O sources. On hydrophilic electrodes with the action\nof sulfonimide anions, hydrophilic H<sub>2</sub>O<sub>2</sub> can\nbe enriched within the double layer for direct oxidation while hydrophobic\ncyclohexanone can be simultaneously accumulated for rapidly reacting\nwith the reactive oxygen species. This work not only enriches the\nelectrified method of the ancient B–V oxidation by using only\nH<sub>2</sub>O<sub>2</sub> toward monomer production of biodegradable\nplastics but also emphasizes the critical role of the interfacial\nionic environment for electrosynthesis systems that may extend the\nscope of activity optimization.