Atomic-level engineering of anisotropically nanoporous graphyne membranes for efficient water desalination

Highlights: • Proposal for a new type of anisotropically nanoporous graphyne membrane. • Analysis of the water desalination performance of the proposed membrane. • Investigation of possible ways to increase the water flow while blocking the ions. In this paper, the molecular dynamics simulation method is applied to investigate the possibility of using anisotropically nanoporous graphyne membranes (ANGMs) in water desalination. In the simulations, four ANGMs and three γ-graphyne membranes (graphyne-3,-4,-5) in the pressure range of 50 to 250 MPa are used to analyze the effect of pressure and membrane pore size on system performance. The reason for using γ-graphyne membranes is to compare their permeability and ion rejection with the proposed ANGMs to get a better insight into the performance of ANGMs. The results reveal that ANGMs, in addition to having high permeability (7.98–47.14 L/cm²/day/MPa), can block a high percentage of ions thanks to the properly engineered shapes of their nanopores, and also, some of them have more efficient performance than γ-graphyne membranes. Furthermore, the mechanism of high ion-rejection of ANGMs and the effects of their pore shapes on their desalination performance are investigated, in detail. Overall, it can be concluded that, due to the high permeability (about 2–3 orders of magnitude larger than reverse osmosis membrane) and high ion rejection, some of the ANGMs can be considered as promising membranes with high potential for water desalination to solve current problems of global water shortage in the future.