Gas adsorption and dynamics in Pillared Graphene Frameworks

Abstract

Pillared Graphene Frameworks are a novel class of microporous materials made by graphene sheets separated by organic spacers. One of their main features is that the pillar type and density can be chosen to tune the material properties. In this work, we present a computer simulation study of adsorption and dynamics of H2, CH4, CO2, N2 and O2 and binary mixtures thereof, in Pillared Graphene Frameworks with nitrogen-containing organic spacers. In general, we find that pillar density plays the most important role in determining gas adsorption. In the low-pressure regime (≲10 bar) the amount of gas adsorbed is an increasing function of pillar density. At higher pressure the opposite trend is observed. Diffusion coefficients were computed for representative structures taking into account the framework flexibility that is essential for assessing the dynamical properties of the adsorbed gases. Good performance for the gas separation in CH4/H2, CO2/H2 and CO2/N2 mixtures was found, with values comparable to those of metal-organic frameworks and zeolites.