The effect of gme topology on multicomponent adsorption in zeolitic imidazolate frameworks

Abstract

We employ a simulation approach to study the adsorption of single, binary and ternary mixtures on eight gme Zeolitic Imidazolate Frameworks (ZIFs) at 298 K. Four adsorbate fluids were considered; carbon dioxide, methane, nitrogen and water. We compute the high pressure adsorption density profiles inside the micropore channels of each crystal. The profiles are compared directly for the different structures and adsorbate components and used to highlight the influence of the imidazolate ligands on pure and competitive adsorption. ZIFs with long ligands reveal an additional, accessible to the fluid space detected for the first time. This is a wedged volume on one direction of the pore walls, shaped thus because the long ligands tilt in order to be connected. We estimate the pressure required for water to become the dominating competing adsorbate within different crystal cavities. The simulated data for CO₂ adsorption in ZIF69 strongly correlate with a set of Raman spectroscopy intensity values that correspond to the same adsorbate–adsorbent system.