AUTHOR=Vekeman Jelle , Faginas-Lago Noelia , Lombardi Andrea , Sánchez de Merás Alfredo , García Cuesta Inmaculada , Rosi Marzio 

TITLE=Molecular Dynamics of CH4/N2 Mixtures on a Flexible Graphene Layer: Adsorption and Selectivity Case Study

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 7 - 2019

YEAR=2019

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00386

DOI=10.3389/fchem.2019.00386

ISSN=2296-2646

ABSTRACT=We theoretically investigate flexible graphene layers, proposing them as membranes of subnanometer size suitable for CH$_{4}$/N$_{2}$ separation and gas uptake. The potential energy surfaces, representing the intermolecular interactions within the CH$_{4}$/N$_{2}$ gaseous mixtures and between the graphene layers and the molecules, have been formulated in an internally consistent way. More specifically, by adopting the so-called Improved Lennard-Jones (ILJ) potential, which is far more accurate than the traditional Lennard-Jones potential routinely used to predict static and dynamical properties of matter. Previously derived ILJ force fields are used to perform extensive molecular dynamics simulations on graphene's ability to separate and adsorb the CH$_{4}$/N$_{2}$ mixture. Furthermore, the intramolecular interactions within graphene were explicitly considered since they are responsible for its flexibility and the consequent out-of-plane movements of the constituting carbon atoms. The influence of introducing flexibility in the graphene sheet on its adsorption ability is assessed via comparison against the adsorption on a rigid graphene sheet. The accuracy of the potentials guarantees a quantitative description of the interactions and realistic results for the dynamics, indicating that the flexible graphene is well capable of separating the CH$_{4}$/N$_2$ mixture. Such properties make these nanostructures versatile materials competitive with other carbon-based adsorbing membranes suitable to cope with CH$_{4}$ and N$_2$ adsorption