Probing adsorbent heterogeneity using Toth isotherms

Abstract

The binding affinity distribution is a fingerprint of the adsorbent heterogeneity. In chromatographic separations, the affinity distribution determines the molecular recognition capability of the stationary phases. In gas storage and separation applications, the affinity distribution decides the selectivity towards a target molecule. The end application of almost every molecular recognizing material like molecularly imprinted polymers (MIPs) critically depend on their affinity distribution. In this work, we develop two simple analytical expressions by coupling a numerical technique with the widely used Toth isotherms. These models are universally applicable and can accurately characterize different classes of industrially-important adsorbents that include metal organic frameworks, carbon allotropes and chromatographic stationary phases for their selectivity, binding affinity and adsorption site heterogeneity. The models require only the Toth isotherm parameters to characterize both homogeneous or heterogeneous adsorbents.