Li+ Selectivity of Carboxylate Graphene Nanopores Inspired by Electric Field and Nanoconfinement

The regulation of the ion selectivity by electric field and ion association on the Li+ selectivity of carboxyl functionalized graphene nanopores are investigated by molecular dynamics simulation. Carboxylate graphene nanopores of sub-2 nm exhibit excellent Li+ selectivity under the electric field of 1.0 V nm-1 . The results show that ion association inspired by electric field may be a key factor affecting ion selectivity of sub-2 nm nanopores. The ion association of Mg2+ and Cl- can be promoted obviously near the nanopores under the electric field of 1.0 V nm-1 . The migrating of Mg2+ can be retarded by stable clusters of Mg2+ and Cl- formed near nanopores. The degree of association of Li+ with Cl- is relatively low and the disassociation of the Li+ cluster is easier so that Li+ can more easily pass through the nanopores. These results gain insight into the effect of ion association inspired by electric field and nanoconfinement of graphene nanopore on Mg2+ /Li+ separation, and provide helpful information for the application of nanoporous materials in extraction of Li+ ion from salt-lake brine.