Theoretically designed two-dimensional γ-C₄O as an effective gas separation membrane for hydrogen purification

A high-performance gas separation membrane for hydrogen (H₂) purification is still highly desirable for the sustainable development of our society. Based on the structure of γ-graphyne, we theoretically designed the two-dimensional nanomaterials γ-C₄X (X = O, S or Se) with intrinsic pores that may be suitable for gas separation. By first-principles calculations, we obtained the geometric structures of γ-C₄X, and confirmed that γ-C₄O and γ-C₄S are stable at room temperature. Due to the moderate size of the intrinsic pores, γ-C₄O exhibits a lower diffusion barrier and higher permeance for H₂ than those of γ-C₄S. It is worth noting that at room temperature, the high selectivity (10¹⁹) for separating H₂ from a H₂/CH₄ mixture by γ-C₄O shows great potential for H₂ purification. Moreover, the classic molecular dynamics simulations at 300 K demonstrate that H₂ can easily permeate through the intrinsic pores of γ-C₄O membranes with high permeability and selectivity, which supports our first-principles calculations.