Interlayer spacing control of boron nitride sheets with hydrated cations

Two-dimensional (2D) materials are widely used in various fields, among which the application prospect in filtering and purifying water resources is broad. An important factor in sieving water molecules and other substances is the interlayer spacing of 2D material membranes. The interlayer spacing of graphene oxide and graphene membranes can be controlled by hydrated cations because of hydrated cation–π interaction. Similarly, our simulations show that hydrated cations can also control the interlayer spacing between hexagonal boron nitride (h-BN) sheets, which are smaller than that of graphene oxide sheets and graphene sheets. The interlayer distances are 8.70, 8.62, 7.68, 8.21, 8.93, 8.11 and 8.18 Å for hydrated Li+, Na+, K+, Mg2+, Ca2+, Cu2+ and Zn2+, respectively. Both hydration energy and the radius of the hydrated cation are deciding factors for monovalent hydrated cations and divalent hydrated cations in affecting the h-BN layer spacing. Further calculations indicate that unlike graphene and graphene oxide dominated by the hydrated cation–π interaction, the interactions between h-BN sheets and hydrate cations are mainly hydrogen bonds. However, there is an obvious hydrated cation–π interaction between hydrated K+ and the h-BN sheets. Our results are helpful for future ion sieving applications using the h-BN membranes.