Electric field tunable Li+ selectivity by eliminating coulomb blockage effect of phosphonic acid-modified graphene nanopores: A molecular simulation study

Abstract The selective Mg2+/Li+ separation of phosphonic acid-modified graphene nanopores was investigated by molecular dynamics simulations. The results show that the dehydration of ions and the interaction of ions with functional groups are two main factors for the Li+ preference of a graphene nanopore under an electric field of a given intensity. As the pore size and the driving force of ion transportation increase, the influence of these two factors on ion penetration will be less effective; thus, the Li+ selectivity declines. The conduction of Li+ can be impeded due to the blockage effect of Mg2+ on nanopores. By applying a proper electric field perpendicular to the direction of ion penetration, the blockage effect can be eliminated, and thus, the nanopores show extremely high Li+ selectivity. This work provides inspiration for the realization of high-efficiency ion screening and desalination using nanoporous membrane materials.