(678a) Propane Adsorption on ZIF-8

We present the results of an adsorption isotherm study of Propane on the metal-organic framework ZIF-8. This material undergoes a structural transition (“gate-opening”) as a function of increasing pressure and sorbent loading for many sorbates. Gate-opening manifests itself in the isotherm data as a quasi-vertical substep, corresponding to an increase in the amount that can adsorb in the ZIF-8. We measured multiple isotherms over a temperature range of nearly 100 K between the triple point and critical point temperatures for bulk Propane. In the range studied, we did not find in any of the isotherms the characteristic substep indicative of the gate-opening. It is possible that the temperature range over which this transition would manifest in the data simply has not been explored in our measurements. The adsorption isotherm data was used to determine the isosteric heat of adsorption of Propane on this sorbent as a function of sorbent loading. The resulting isosteric heat plot contains a dramatic peak which might be associated with the gate opening transition. At sorbent loadings below that which corresponds to the peak, isosteric heat values are less than the latent heat of condensation for Propane. We have studied the kinetics of adsorption for this system using the linear driving force model to obtain concise summaries of kinetic data for multiple temperatures. Times to reach fractional uptakes of 0.999 for mass loading data corresponding to individual points along the isotherms will be presented. Additionally, effective specific surface area measurements obtained from the Point-B and BET methods will be presented.