Chemical recycling of hydrofluorocarbons by transfer fluorination

Fluorochemicals improve our quality of life; however, there is increasing concern over how they are produced and their negative effects on health and the environment. Here we report an approach to the recycling of fluorochemicals. Treatment of hydrofluorocarbons with a potassium base (KHMDS or KO^tBu) results in rapid defluorination to produce anhydrous potassium fluoride. This potassium fluoride can then be used to prepare a wide range of fluorinated organic and inorganic molecules, including sulfonyl fluorides, aryl fluorides, alkyl fluorides and a range of p-block fluorides, in an overall one-pot transfer fluorination process. The scope of fluorochemicals that can be recycled by transfer fluorination includes industrially relevant refrigerants (hydrofluorocarbons), hydrofluoroolefins, fluoroethers—including anaesthetics and battery additives—perfluorooctanoic acid and poly(vinylidene) difluoride. Aspects of the transfer fluorination mechanism have been investigated using density functional theory calculations, and approaches to scale up using batch (50 g) and flow (1.5 g h⁻¹) chemistry are presented. (Figure presented.)