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 separation in recent years. However, the challenge lies in the rational design of GDYs for fast and selective H permeation. By MD and DFT calculations, several flexible GDYs were constructed to investigate the permeation properties of four pure gas (H, N, CO, and CH) and three equimolar binary mixtures (H/N, H/CO, and H/CH) in this study. When the pore size is smaller than 2.1 Å, the GDYs acted as an exceptional filter for H with an approximately infinite H 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 permeation. After understanding the mechanism, the H permeance of the mixtures of H/CO was further increased to 2.84 × 10 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 permeation crossing GDYs, indicating that the GDY membrane could be a potential candidate for H purification.