Abstract Molecular crystals of dipeptides with a high density of uniform pores have received growing interest for gas separation. Particularly, hydrophobic dipeptides can form one-dimensional straight pores with sizes ranging from 0.37 to 0.50 nm. A molecular simulation study is reported here to investigate the membrane separation of CO2/N2 and CO2/CH4 mixtures in eight dipeptides namely Ala-Val (AV), Val-Ala (VA), Ala-Ile (AI), Ile-Ala (IA), Val-Ile (VI), Ile-Val (IV), Val-Val (VV) and Leu-Ser (LS). The gas permeation and separation performance are evaluated using a molecular dynamics simulation method with a constant-pressure difference. The pore size and helicity are revealed to be the key factors governing permeation. A higher permeability can be achieved in a dipeptide membrane with a larger pore size or a lower helicity. Among the eight, six (AV, LS, AI, VA, VV and VI) surpass the Robeson upper bound for both gas mixtures. It is identified that AI and AV outperform other dipeptides for CO2/N2 separation, while AI, VA and VV are better for CO2/CH4 separation. The permselective separation of both gas mixtures is dominated by the preferential sorption of CO2 over N2 and CH4, respectively. This simulation study provides microscopic insights into CO2 separation in dipeptide membranes and suggests their potential use for gas separation.

中文翻译：

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用于 CO2 分离的二肽膜：分子模拟研究

摘要 具有高密度均匀孔的二肽分子晶体在气体分离方面受到越来越多的关注。特别地，疏水性二肽可以形成尺寸为0.37至0.50nm的一维直孔。本文报道了一项分子模拟研究，以研究八种二肽中 CO2/N2 和 CO2/CH4 混合物的膜分离，即 Ala-Val (AV)、Val-Ala (VA)、Ala-Ile (AI)、Ile-Ala ( IA)、Val-Ile (VI)、Ile-Val (IV)、Val-Val (VV) 和 Leu-Ser (LS)。气体渗透分离性能采用分子动力学模拟方法进行恒压差评价。孔径和螺旋度被揭示是控制渗透的关键因素。在具有更大孔径或更低螺旋度的二肽膜中可以实现更高的渗透性。八人之中，六（AV、LS、AI、VA、VV 和 VI）超过了两种气体混合物的 Robeson 上限。结果表明，AI 和 AV 在 CO2/N2 分离方面优于其他二肽，而 AI、VA 和 VV 在 CO2/CH4 分离方面表现更好。两种气体混合物的选择性渗透分离分别由 CO2 优先吸附于 N2 和 CH4 主导。该模拟研究提供了对二肽膜中 CO2 分离的微观见解，并提出了它们在气体分离中的潜在用途。