Carbon-Based Nanoporous Networks as Media for the Separation of CO2/CH4 Mixtures: A Molecular Dynamics Approach

Molecular dynamics simulation techniques have been employed to investigate the separation of a CO2/CH4 equimolar mixture at ambient temperature, using a recently designed 3D-carbon-based nanostructured model material as a potential molecular sieve. The calculations performed have shown that the carbon dioxide molecules are preferentially adsorbed over the methane ones, yielding a very satisfactory selectivity for carbon dioxide. The residence time correlation functions and mean-square displacements of the CO2 and CH4 molecules adsorbed in the nanopores have also been calculated predicting higher diffusivities for the methane molecules inside the nanostructured material, but significantly lower than in the bulk gas mixture. The translational and reorientational dynamics of the CO2 and CH4 molecules have also been investigated, indicating that in the case of CO2 they are more sensitive upon confinement. The results obtained signify that the rational design of novel carbon-based nanostructured porous networks might lead to the development of promising candidates for the separation of CO2/CH4 mixtures, exhibiting important applications in natural gas technology.