Characteristics of CO₂ Adsorption and Permeability of Porous Carbon-Nitrogen Membranes Coupling-regulated by Charge and Strain

In order to promote the development of new materials and technologies to effectively capture and separate CO₂, a new charge-and strain-controlled gas capture and permeation method is proposed, which has the advantages of reversibility and controllable dynamics. The molecular dynamics (MD) simulation and first-principles density function (DFT) calculation are used to analyze the effects of CO₂ capture and penetration on porous g-C₉N₇ nanosheets with different charge densities and stress controls. Through charge regulation, the molecular permeance of CO₂ can reach 5.94×10⁷ GPU (0.019 899 mol/(s·Pa·m²)). Under tensile strain conditions, the CO₂ permeance increases with the increase of tensile strain, and the maximum permeance of 7.5% tensile strain rate g-C₉N₇ membrane is 3.61×10⁷ GPU(0.012 094 mol/(s ·Pa ·m²)). More interestingly, a feasible way is explored to combine negative charge with strain engineering to study synergistic effects. When the negative charge is 1 e and the tensile strain rate is 3.0%, the CO₂ permeability reaches 3.18×10⁷ GPU(0.001 065 mol/(s ·Pa ·m²)), which is 9 times of that when only 1 e is added and 8 times of that when only 3.0% is added. These results provide useful guidance for the development of advanced materials with highly controllable CO₂ capture and separation properties.