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In this study, we demonstrate that defected h--BN (1B-3N and 1N-3B defects) can be used as a suitable membrane for hydrogen purification and helium separation using density functional theory (DFT) calculations and molecular dynamics simulations (MD). At 300 K, DFT calculations show that the selectivity of $H_2/CO_2$, $H_2/N_2$, $H_2/CO$, and $H_2/CH_4$ are $1 \times 10^{26}$, $6 \times 10^{49}$, $2 \times 10^{40}$, and $1 \times 10^{94}$ respectively for 1B-3N, while they are $9 \times 10^{13}$, $1 \times 10^{21}$, $1 \times 10^{19}$, and $1 \times 10^{42}$ for 1N-3B. Although selectivity of 1B-3N defect is much higher than 1N-3B defect, the permeance of this defect is much lower than industrial limits. To confirm the result obtained by DFT calculations for gas separation performance of 1N-3B defect, the classical molecular dynamics simulations were further carried out. Molecular dynamics simulations confirm the results of DFT calculations except $H_2/CO_2$. It demonstrates that the selectivity of $H_2$ will grow, if temperature rises. This phenomenon is explainable by probability density distribution of the $CO_2$ molecules at various temperatures. These simulations show that h-BN has good adsorption for $CO_2$ molecules and is a suitable membrane for $CO_2$ capture. Finally, the excellent selectivity along with acceptable permeance makes 1N-3B defects on h-BN, the promising membrane for He separation and $H_2$ purification. |
