Evaluation of Ideal AdsorbedSolution Theory as aTool for the Design of Metal–Organic Framework Materials.

As a class of porous materials, metal–organicframeworks(MOFs) show promise for the adsorption-based separation of mixturesof gases. The design of any process involving selective adsorptionrequires knowledge of mixture adsorption isotherms. Ideal adsorbedsolution theory (IAST) predicts mixture adsorption equilibria usingonly single-component data, thereby minimizing the need for experimentaladsorption data. In this work we perform a systematic study of theapplicability of IAST to MOFs by using grand canonical Monte Carlo(GCMC) simulations to investigate the suitability of IAST for theprediction of the adsorption of mixtures of molecules of differingsizes, asphericities, and polarities in a range of structurally differentMOFs. We show that IAST is generally accurate for MOFs. Where we findIAST is less accurate, deviations result from both mixture effects,in the form of nonidealities in the adsorbed phase, and characteristicsof the adsorbent structures. In terms of the MOF structure, departuresfrom IAST are a consequence of heterogeneities both on the scale ofthe unit cell and on shorter length scales, whereby competition foradsorption sites has a strong influence. [ABSTRACT FROM AUTHOR]