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

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$\equiv$C$-$C$\equiv$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. 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.

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