Identification of Metal-Organic Framework Materials for Adsorption Separation of Rare Gases: Applicability of Ideal Adsorbed Solution Theory (IAST) and Effects of Inaccessible Framework Regions

A collection of >3000 MOFs with experimentally confirmed structures were screened for performance in three binary separations: Ar/Kr, Kr/Xe, and Xe/Rn. 70 materials were selected for further analysis, and calculations were performed to account for inaccessible regions. Single component GCMC calculations were performed to parametrize LAST calculations on these 70 materials. An approach that avoids possible imprecision in IAST due to curve-fitting of single component isotherms is introduced. The precision of IAST for these gas pairs was confirmed with extensive binary GCMC calculations. For each binary separation, materials were identified with predicted performance that surpasses the state of the art. A significant number of materials were found to be reverse selective in the sense that a smaller gas species is preferably adsorbed over a larger species. The physical origin of this phenomenon is explained. The effect of temperature on separation performance was also examined.