LAUSR

Graphene membranes with subnanopores are considered to be the next-generation materials for water desalination and ion separation, and their performance is mainly determined by the ion relative selectivity of the pores. However, the origin of this phenomena has been controversial for decades, which strongly limits the development of related applications. Here, using direct Au ion bombardment, we fabricated the desired subnanopores with average diameters of 0.8±0.16 nm in monolayer graphene. The pores showed the distinguishing capability among K+, Na+, Li+, Cs+, Mg2+, and Ca2+ cations, and the observed K+/Mg2+ selectivity ratio was over 4. With further molecular dynamics simulations, we demonstrated that the ion selectivity is primarily contributed by the dehydration process of ions, which can be quantitatively described by the ion-dependent free-energy barriers. This work is hopeful to further enhance the ion selectivity of graphene nanopores, and also presents a new paradigm for improving the performance of other nanoporous atomically thin membranes, such as MXenes and MoS2.