Organic molecules of intrinsic microporosity: Characterization of novel microporous materials

Abstract

Molecular simulations were used in this work to characterise a new class of microporous material: organic molecules of intrinsic microporosity (OMIMs). Molecular dynamics simulations were used to generate the material’s samples, and grand canonical Monte Carlo simulations of argon adsorption were used to ascertain the relationship between the different structures and the observed properties. Packing behavior, porosity and adsorption capacity have been determined for each system. The final density of the material, as well as the surface area and pore volume depend on the ending group’s bulkiness. Bulkier molecules lead to materials with lower densities, but it was found that the adsorption behavior is not just related to the material’s density, but also to the pore size and shape, which are determined by the way the molecules pack. The relationship between adsorption capacity and physical properties were analyzed and the role of surface area, free volume and enthalpic interaction were used to identify different adsorption regimes. It was found that the uptake of argon at low pressure is proportional to the strength of the adsorbent-adsorbate interaction while at moderate pressure it is dependent on the free volume and surface area.