Adsorption of Benzene in the Cation-Containing MOFs MIL-141

The adsorption of benzene in the cation-containing metal–organic framework (MOF) MIL-141­(Cs) was explored by manometry measurements coupled with Monte Carlo simulations. This joint experimental/modeling approach demonstrates that this solid shows a high affinity for benzene that does not result from a direct interaction between the guest molecules and the Cs⁺ cations, in contrast to what is commonly observed in zeolites. This behavior was attributed to the high degree of confinement of Cs⁺, which prevents any cation detrapping upon adsorption, as revealed by dielectric relaxation spectroscopy and molecular dynamics simulations. This peculiar adsorption behavior is further discussed in relation to that of other alkali extraframework cations including Li⁺, Na⁺, K⁺, and Rb⁺