Rethinking Calcium Fluoride Chemistry

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Fluorine is an essential element for many pharmaceuticals, agrochemicals, anesthetics, materials, and air-conditioning refrigerants, which owe their important properties to the fluorine atoms in their structures. For example, about 20% of marketed drugs and 30% of agrochemicals contain one or more fluorine atoms because they are known to be important for optimizing their mode of action. In turn, this leads to a lower amount of pharmaceutical or agrochemical being needed, in addition to an improved result. In the fields of materials chemistry and energy, fluorinated molecules and plastics are ubiquitous. One example is the use of polytetrafluoroethylene (PTFE) as an anti-stick coating for pans, meaning that less butter or oil needs to be used while cooking. Another example can be found in electrolyzers and fuel cells, used to produce and 'burn' hydrogen produced from renewable energy sources, both of which will be important processes in a sustainable and fossil fuel-free economy. An essential component in these devices is a thin separator (membrane) that is made from fluorinated species.Given their widespread use and numerous benefits, it is unsurprising that the production of fluorine-containing molecules is a very large-scale process. At the moment, all of the fluorine atoms in these high-performance molecules are introduced via the molecule hydrogen fluoride (HF). HF poses severe safety risks as it can penetrate the skin, can quickly cause severe burns, and is toxic as the fluoride ion reacts with calcium in your bones to precipitate calcium fluoride. HF is also very corrosive, capable of reacting with almost all materials, including glass, ceramics, and metals.This dangerous and reactive compound, HF, is made from a very safe and unreactive material: the mineral fluorspar (CaF2). So why does industry not use this material directly to avoid the use of toxic HF? The paradoxical reason is that same unreactivity of CaF2, caused by its poor solubility. No processes are known to date enabling CaF2 to react with an organic substrate to produce a fluorinated product in an efficient manner.The aim of this research is to change this situation and develop the first method(s) to use CaF2 directly in the synthesis of fluorinated molecules. This process will be developed in such a way that it can be applied in industry, where currently over 3 million tons of CaF2 is used to produce HF, making the research potentially highly impactful. Therefore, this research fits very well within EPSRC's Manufacturing the Future research theme.