C2N: an excellent two-dimensional monolayer membrane for He separation

Abstract

Using the first-principles density functional theory (DFT) and molecular dynamics (MD) simulations, we investigate the He separation performance of a porous C₂N monolayer synthesized recently. The DFT calculations demonstrate that the porous C₂N monolayer is stable enough to be used as a gas separation membrane and the porous C₂N monolayer with a suitable pore size presents a surmountable energy barrier (0.13 eV) for He molecules passing through the membrane. Furthermore, the porous C₂N monolayer shows an exceptionally high selectivity for He/Ne (Ar, CH₄, CO₂, N₂, etc.) in a wide range of temperatures. Besides, using MD simulations we demonstrate that the porous C₂N monolayer exhibits a He permeance of 1 × 10⁷ GPU at room temperature, which is much higher than the value (20 GPU) in current industrial applications. Therefore, the porous C₂N monolayer should be an excellent candidate for He separation from natural gas, due to its high selectivity and excellent permeability.