Nitrogen-Modified Graphdiyne as a Promising Membrane for Helium Separation: First-Principles and Molecular Dynamics Simulations

The He separation performance of the N-modified graphdiyne monolayer (N-GDY) was studied by using both the first-principles density functional theory (DFT) and molecular dynamics (MD) simulations. The high cohesive energy of 7.24 eV/atom confirmed the strong stability of N-GDY for a gas separation membrane. Based on the calculations, the N-GDY membrane was found to exhibit extremely high He permeance (4.8 ×10 -3 mol/m 2 ·s·Pa at 100 K) and selectivities of He/H 2 O, He/Ar, He/N 2 , He/CO, He/CO 2 , and He/CH 4 (10 2 ~10 12 at 300 K). Therefore, N-GDY should be a good candidate for He separation from natural gas.