Water Purification across MoS$_{2}$ Nano-porous Membranes

A 2D material, molybdenum disulfide (MoS$_{2})$, is proposed as a nano-porous membrane for water desalination. By performing detailed molecular dynamics simulations, we find that salt ions are rejected efficiently across a single-layer MoS$_{2}$ while water permeates at high rates. Depending on the pore area, which ranges from 20 to 60 {\AA}$^{2}$, the nanopore allows less than 12{\%} of ions to pass through even at theoretically high pressures of 350 MPa. Water permeation across the MoS$_{2}$ membrane is found to be as high as 12 L/cm$^{2}$/day/MPa which is at least two orders of magnitude higher than that of other existing nano-porous membranes. Pore chemistry is shown to be one of the important factors leading to large water fluxes. MoS$_{2}$ pore edges terminated with only molybdenum atoms result in higher fluxes which are about 70{\%} higher than that of graphene nanopores. These findings are explained and supported by the permeation coefficients, energy barriers, water density and velocity distributions in the pores.