A high selective and permeable C7N6 monolayer membrane for H2 purification: First-principles and molecular dynamics simulations

Designing efficient membranes for hydrogen purification and separation is highly desired because of the development of the hydrogen economy. Using the combination methods of density functional theory (DFT) calculations and molecular dynamics (MD) simulations, we theoretically investigated the performance of the C7N6 monolayer for H2 purification and separation. Our DFT calculations indicate that H2 molecules would permeate through the C7N6 monolayer with a relatively low energy barrier (0.689 eV), and the C7N6 monolayer has an ultra-high selectivity of 7.47 x 106, 5.71 x 109, 1.19 x 1011, and 1.08 x 1012 for H2/O2, H2/CO2, H2/CO, and H2/N2 at even high temperature of 500 K, respectively. The MD simulations confirmed that the high selectivity and permeability of the H2 gas above 500 K. Even at higher temperatures of 800 to 1000 K, almost all of H2 gas can be separated by the C7N6 membrane without any other foreign gases passing through the membrane, indicating that the C7N6 monolayer can be used as an ultra-high performance H2 purification and separation membrane on the practical conditions as the C7N6 monolayers are dynamically, thermodynamically, and mechanically stable.