Atomistic Modeling of Water Thermodynamics and Kinetics within MIL-100(Fe)

Abstract

Molecular dynamics computer experiments were conducted to study the thermodynamics and kinetics of the water-sorbed phase within a digitized hybrid (inorganic–organic) iron carboxylate sorbent, the MIL-100(Fe), relying on a synergy of statistical mechanics-based methodology and the time evolution of the system captured by classical mechanics. To achieve sufficient statistics, the entire unit cell of this extremely large host material was utilized, and consequently, the offset of the imposed computational burden became one of the tasks of the presented study. Analysis of sorption thermodynamics reveals that the kind of the MIL-100 terminal species (fluorine and water, bound to iron), as well as their relative position around the cavity joints of the small and large mesopore networks of this material, may tune the sorption phenomena and control the guest population rate within the two pore systems. Computed singlet and pair density distributions along with the transport predictions of water in the host material support the findings of thermodynamics and interpret the diffusivity loading dependence on the basis of the spatial free energy distribution of the guest phase.