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.

Key words: Graphdiyne, Strain, CO₂ separation, Molecular dynamics, Density functional theory

摘要： 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.

关键词: Graphdiyne, Strain, CO₂ separation, Molecular dynamics, Density functional theory