The adsorption and diffusion of small alcohols in ZIF-8 and ZIF-90 were examined using a combined experimental and modeling approach. Grand canonical Monte Carlo simulations predicted that both materials exhibited aslight adsorption selectivity for ethanol over methanol, in good agreement with experimental data. The adsorption uptake of the alcohols at low pressures was found to be significantly higher for ZIF-90 than ZIF-8. The simulations indicated that this was due to hydrogen bonding between the alcohols and the carbonyl group of ZIF-90, but the effect was not strong enough to cause appreciable flexibility of the ZIF-90 framework during adsorption. Also reported were alcohol self-diffusivities and Arrhenius parameters as measured using pulsed field gradient NMR and molecular dynamics simulations. The diffusivities measured using pulsed field gradient NMR indicated that the diffusion selectivity of methanol over ethanol was significantly higher in ZIF-8 (S = 229) than in ZIF-90 (S = 6) at 25C.

Adsorption and Diffusion of Small Alcohols in Zeolitic Imidazolate Frameworks ZIF-8 and ZIF-90. J.A.Gee, J.Chung, S.Nair, D.S.Sholl: Journal of Physical Chemistry C, 2013, 117[6], 3169-76