Enhanced Selective Hydrogen Permeation through Graphdiyne Membrane: A Theoretical Study

Graphdiyne (GDY), with uniform pores and atomic thickness, is attracting widespread attention for application in H(2) separation in recent years. However, the challenge lies in the rational design of GDYs for fast and selective H(2) permeation. By MD and DFT calculations, several flexible GDYs were constructed to investigate the permeation properties of four pure gas (H(2), N(2), CO(2), and CH(4)) and three equimolar binary mixtures (H(2)/N(2), H(2)/CO(2), and H(2)/CH(4)) in this study. When the pore size is smaller than 2.1 Å, the GDYs acted as an exceptional filter for H(2) with an approximately infinite H(2) selectivity. Beyond the size-sieving effect, in the separation process of binary mixtures, the blocking effect arising from the strong gas–membrane interaction was proven to greatly impede H(2) permeation. After understanding the mechanism, the H(2) permeance of the mixtures of H(2)/CO(2) was further increased to 2.84 × 10(5) GPU by reducing the blocking effect with the addition of a tiny amount of surface charges, without sacrificing the selectivity. This theoretical study provides an additional atomic understanding of H(2) permeation crossing GDYs, indicating that the GDY membrane could be a potential candidate for H(2) purification.