Gas Transport Mechanisms through Molecular Thin Carbon Nanomembranes

Molecular thin carbon nanomembranes (CNMs) synthesized by electron irradiation induced cross‐linking of aromatic self‐assembled monolayers (SAMs) are promising 2D materials for the next generation of filtration technologies. Their unique properties including ultimately low thickness of ≈1 nm, sub‐nanometer porosity, mechanical and chemical stability are attractive for the development of innovative filters with low energy consumption, improved selectivity, and robustness. However, the permeation mechanisms through CNMs resulting in, e.g., an ≈1000 times higher fluxes of water in comparison to helium have not been yet understood. Here, a study of the permeation of He, Ne, D2, CO2, Ar, O2 and D2O using mass spectrometry in the temperature range from room temperature to ≈120 °C is studied. As a model system, CNMs made from [1″,4′,1′,1]‐terphenyl‐4‐thiol SAMs are investigated. It is found out that all studied gases experience an activation energy barrier upon the permeation which scales with their kinetic diameters. Moreover, their permeation rates are dependent on the adsorption on the nanomembrane surface. These findings enable to rationalize the permeation mechanisms and establish a model, which paves the way toward the rational design not only of CNMs but also of other organic and inorganic 2D materials for energy‐efficient and highly selective filtration applications. Carbon nanomembranes (CNMs) made from self‐assembled monolayers are promising candidates for filtration applications. In this study, the gas permeation mechanism of CNMs is investigated by examining the permeation of various gases through CNM made from [1″,4′,1′,1]‐terphenyl‐4‐thiol at different temperatures using mass spectrometry. It is demonstrated that permeation rates of the gases depend on their adsorption on the CNM surface.