Theoretical investigation on two-dimensional conjugated aromatic polymer membranes for high-efficiency hydrogen separation: The effects of pore size and interaction

WR Zhai and MH Wang and S Liu and SY Xu and H Dong and L Wang and SX Wei and ZJ Wang and SY Liu and XQ Lu, SEPARATION AND PURIFICATION TECHNOLOGY, 299, 121674 (2022).

DOI: 10.1016/j.seppur.2022.121674

Based on two-dimensional conjugated aromatic polymer (2D-CAP), CAP-1S/CAP-1P monolayers were designed by substituting N with S/P atoms for H2 purification. By using MD and DFT approaches, the H2 purification performance and separation mechanisms of CAP-1S/CAP-1P membranes were investigated. Results showed that ultrahigh H2 permeances of 3.546 x 10-5 and 2.593 x 10-4 mol m-2 s- 1 Pa-1 were obtained in CAP-1S/CAP-1P, which were almost 104-105 times larger than the industrially acceptable standard. The selectivities of H2 over CO2/CO/CH4/N2 ranged from 5.719 x 1018 to 3.683 x 1039 in CAP-1S and 4.554 x 1013 to 2.153 x 1033 in CAP1P. From a statistic viewpoint, the CAP-1S/CAP-1P membranes exhibited complete selectivities of H2 over CO2/ CO/CH4/N2. The cohesive energies confirmed the high stabilities of CAP-1S/CAP-1P membranes. The minimum energy pathways, energy profiles, electron density, and charge density difference were analyzed to illustrate the significant impact of precise pore size on the H2 separation performance. From a statistic mechanics view, the interaction between gases and CAP-1S/CAP-1P membranes indicated that the long-range Coulomb interactions dominated the gas diffusion processes. Results of this work highlighted CAP-1P as a promising H2 separation membrane and elucidated the promotion mechanism by fine-tunning pore size and interaction between gases and membranes to balance the H2 permeance and selectivity jointly.

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