Isoelectronic Doping and External Electric Field Regulate the Gas-Separation Performance of Graphdiyne

The first-principles calculations and molecular dynamics (MD) simulations have been used to explore the effects of boron nitride (BN) doping and an external electric field on the diffusion of gases (N-2, CO, H-2, CO2, and CH4) through a graphdiyne (GDY) membrane. BN-doped graphdiyne-like monolayers (GDY-BN and GDY-fBN) were predicted to have better permeability than the GDY membrane for the diffusion of these molecules and maintain high selectivity for hydrogen purification. The presence of an external electric field may regulate the diffusion behavior of CO2 and CO through the membrane, while other gas molecules are almost not influenced, which can improve the permselectivity toward gas separation. MD simulations reveal an unexpected temperature effect on gas diffusion through GDY-BN, which may be ascribed to a balance between the thermally driven translation and rotation motions. The rise in temperature increases the driving force for molecular translation through the membrane, but the thermal speedup of rotational motion may reduce the possibility of gases passing through the membrane in the optimal axial direction of molecules with the lowest diffusion barriers. The present results suggest that the gas-separation performance can be manipulated by regulating the charge distribution of the pore and using an external electric field.