Guest Diffusion in Interpenetrating Networks of Micro- and Mesopores

Abstract

Pulsed field gradient NMR is applied for monitoring the diffusion properties of guest molecules in hierarchical pore systems after pressure variation in the external atmosphere. Following previous studies with purely mesoporous solids, also in the material containing both micro- and mesopores (activated carbon MA2), the diffusivity of the guest molecules (cyclohexane) is found to be most decisively determined by the sample "history": at a given external pressure, diffusivities are always found to be larger if they are measured after pressure decrease (i.e., on the "desorption" branch) rather than after pressure increase (adsorption branch). Simple model consideration reproduces the order of magnitude of the measured diffusivities as well as the tendencies in their relation to each other and their concentration dependence.

Mass Transport of Volatile Molecules in Porous Materials: Evaporation–Condensation Phenomena Described by NMR Diffusometry

“…11,26,27 However, for fast equilibration, an effective diffusion constant is observed, which is a weighed average over all states 26…”

Diffusion Study by IR Micro-Imaging of Molecular Uptake and Release on Mesoporous Zeolites of Structure Type CHA and LTA

“…This is related to the fact that mesopore diffusion is highly sensitive to the pore phase state [19] whose establishment has remained, for more than a century, a hot topic of discussion [20,21,22,23]. Investigating history-dependent molecular diffusion in materials with hierarchical pore architecture has thus become an attractive new access to studying the equilibration process in complex pore systems [24,25]. …”

Peculiarities of the charge transport in the gas discharge electronic device with irradiated porous zeolite

“…First of all, it suggests that only the decrease in the mean diffusion path in the nanopores, 27 and second, the larger pores directly contribute to the kinetics and thermodynamics of the diffusion process. 28,29 For this reason, the current value depends on the time since the concentration of charge carriers in the sample volume is gradually changing. In the dehydrated sample, this effect was observed during the experiment, stable current value is set almost immediately after applying a DC voltage.…”