Increased CO2/N2 selectivity by stepwise fluorination in isoreticular ultramicroporous metal–organic frameworks†

Exploration of porous adsorbents with high CO₂/N₂ selectivity is of great significance for reducing CO₂ content in the atmosphere. In this study, a series of isoreticular ultramicroporous fluorinated metal–organic frameworks (MOFs) were prepared to explore the benefits of fluorinated ultramicropores in improving CO₂/N₂ selectivity. Gas adsorption measurements revealed that the increase in the number of fluorine atoms in a ligand molecule leads to the increased CO₂ uptakes and CO₂/N₂ selectivity. Theoretical calculations indicate that the interaction between the fluorine atoms and adsorbed CO₂ molecules enhances the CO₂-philicity, offering useful insight into the improvement of CO₂/N₂ selectivity in isoreticular frameworks.