Fig. 2.

MD simulations of the gas permeation through the MXene membrane compared with the experimental results. a Single-gas permeabilities through a 2-μm-thick MXene membrane as a function of the gas kinetic diameter at 25 °C and 1 bar. Inset shows the selectivity of H₂ relative to the other gases in both the single-gas and equimolar mixed-gas permeation studies. b Comparison of the experimental and MD simulated selectivities of H₂/CO₂ and H₂/N₂ in both the single-gas and mixed-gas permeations. c The number of gas molecules that passed through the MXene membrane in MD simulation as a function of simulation time for single-gas permeation. For H₂, only the first 10 ns of the simulation are shown because of its fast permeation. By contrast, only two molecules pass through the MXene membrane during the 200-ns-long simulation for CO₂ or N₂. The CO₂ curve fluctuates because of CO₂ adsorption–desorption on the MXene membrane. d Simulation snapshots at 0, 30, 100, and 300 ns for two sets of mixed-gas permeation systems: (H₂ + CO₂) and (H₂ + N₂). Note that H₂ was modeled by united-atom force field. The MXene membrane was composed of two nanosheets with a free spacing of 0.35 nm located in the middle of the simulation system. In the beginning (t = 0 ns), 30 H₂ and 30 CO₂ (or N₂) molecules were present in the feed chamber, which permeated through the MXene membrane to the evacuated permeate chamber. The details can be found in section of “Methods”