Highly Selective Adsorption of Fluorinated Gases by Porous Organic Cages - Effects of Fluorinated Side-Chains

Perfluorocarbons (PFCs) as well as related gases such as sulfur hexafluoride (SF₆) or nitrogen trifluoride (NF₃) are examples of F-gases, a subclass of per- and polyfluoroalkyl substances (PFAS). F-gases are anthropogenic greenhouse gases with the highest global warming potentials known and thus contribute significantly to global warming. To reduce their amount in the atmosphere, selectively adsorbing materials would be beneficial, but such materials are rare. A homologous series of porous organic cages with fluorinated side-chains is synthesized and depending on the targeted gas as well as operating temperature, different cages have high selectivities for certain F-gases against N₂, CO₂, and O₂. Within this series, new benchmark selectivities against, e.g., perfluoro propane (PFC-218) and perfluoro cyclobutane (PFC-318) have been achieved based on attractive fluorine-fluorine interactions. Furthermore, these interactions are exploited for the first time in the adsorption of sulfur hexafluoride and nitrogen trifluoride.