Strain-controlled graphdiyne membrane for CO2/CH4 separation: First-principle and molecular dynamic simulation

Abstract

Abstract Tensile strain of porous membrane materials can broaden their capacity in gas separation. In this work, using van der Waals corrected density functional theory (DFT) and molecular dynamics (MD) simulations, the performance and mechanism of CO2/CH4 separation through strain-oriented graphdiyne (GDY) monolayer were studied by applying lateral strain. It is demonstrated that the CO2 permeance peaks at 1.29 × 106 gas permeation units (GPU) accompanied with CO2/CH4 selectivity of 5.27 × 103 under ultimate strain, both of which are far beyond the Robeson's limit. Furthermore, the GDY membrane exhibited a decreasing gas diffusion energy barrier and increasing permeance with the increase of applied tensile strain. CO2 molecule tends to reoriented itself vertically to permeate the membrane. Finally, the CO2 permeability decreases with the increase of the temperature from 300 K to 500 K due to conserving of rotational freedom, suggesting an abnormal permeance of CO2 in relation to temperature. Our theoretical results suggest that the stretchable GDY monolayer holds great promise to be an excellent candidate for CO2/CH4 separation, owing to its extremely high selectivity and permeability of CO2.