Ionic liquid-mediated CO₂/N₂ separation in MoSe₂ nanochannels: a molecular dynamics perspective

In recent years, supported ionic liquid membranes (SILMs) have attracted widespread attention due to their remarkable performance in gas separation. Two-dimensional (2D) nanomaterials, characterized by atomic-scale thickness, high specific surface area, and tunable mass transport pathways, are ideally suited for enhancing the separation efficiency of composite membranes through precise regulation of ionic liquids (ILs) and support architecture. In this study, a composite membrane system was constructed via molecular dynamics (MD) simulations, in which [BMIM][BF₄] was confined within molybdenum diselenide (MoSe₂) interlayers, and its performance in separating CO₂/N₂ mixtures was systematically evaluated. The separation efficiency was optimized by tuning key structural and operational parameters, including interlayer spacing, IL loading, and temperature. The results demonstrate that the optimal separation is achieved at 300 K with an IL loading ratio of 65% and an interlayer spacing of 4 nm. Furthermore, analysis of density distributions and cation orientation elucidated the microstructural characteristics and separation mechanisms of the membrane channels. The confined ILs within the MoSe₂ nanochannels exhibits a structure distinct from its bulk-phase counterpart, showing a stronger tendency to interact with gas molecules. The difference in gas solubility within the IL phase is identified as a key factor driving efficient separation. This study offers theoretical insights and design guidance for the development of 2D nanomaterial-based supported ionic liquid membranes (2D-SILMs) for CO₂/N₂ separation.