In summary, we report a method for the room temperature defluorination of PTFE (and short chain PFAS compounds) that produces a molecular magnesium fluoride reagent. Analysis of the PTFE post modification suggests that the reaction occurs primarily at the surface of the polymer, likely to create unsaturated carbon-carbon bonds within the polymer chain. The magnesium fluoride reagent is readily separated and was shown to be capable of transferring the fluorine atom to a small range of electrophiles. Our study provides proof-of-concept results that show fluoride can be harvested from PTFE and re-used in chemical synthesis.