An insight into clustering of halogenated anesthetics molecules in metal-organic frameworks: Evidence of adsorbate self-association in micropores

In order to better understand the adsorption of volatile halogenated anesthetics on metal organic frameworks (MOFs), sevoflurane vapor adsorption experiments were performed on commercial MOF-177 at different temperatures. Due to the surface homogeneity of such an adsorbent, arising from its almost unimodal pore size distribution and the absence of specific, coordinatively unsaturated adsorption active sites, sevoflurane adsorption isotherms exhibited a peculiar deviation from the Langmuirian behavior. Consequently, they show a "kink" at a specific pressure that increases with increasing equilibrium temperature. Successful modeling of such data by means of the Talu-Meunier equation confirmed clustering of adsorbate molecules inside adsorbent micropores, similarly to water vapor adsorption on activated carbon, which may play an important role when designing a system using MOFs as the potential adsorbents for capturing anesthetics.