A new approach to separate hydrogen from carbon dioxide using graphdiyne-like membrane

Abstract

In order to separate a mixture of hydrogen (H 2) and carbon dioxide (CO 2) gases, we have proposed a new approach employing the graphdiyne-like membrane (GDY-H) using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. GDY-H is constructed by removing one-third diacetylenic (- C ≡ C - C ≡ C -) bonds linkages and replacing with hydrogen atoms in graphdiyne structure. Our DFT calculations exhibit poor selectivity and good permeances for H 2/CO 2 gases passing through this membrane. To improve the performance of the GDY-H membrane for H 2/CO 2 separation, we have placed two layers of GDY-H adjacent to each other which the distance between them is 2 nm. Then, we have inserted 1,3,5-triaminobenzene between two layers. In this approach, the selectivity of H 2/CO 2 is increased from 5.65 to completely purified H 2 gas at 300 K. Furthermore, GDY-H membrane represents excellent permeance, about 10 8 gas permeation unit (GPU), for H 2 molecule at temperatures above 20 K. The H 2 permeance is much higher than the value of the usual industrial limits. Moreover, our proposed approach shows a good balance between the selectivity and permeance parameters for the gas separation which is an essential factor for H 2 purification and CO 2 capture processes in the industry.