Tunable Gas Permeation Behavior through Robust, Freestanding Self-Assembled Metal Nanoparticle Membranes

Membrane-based gas separation offers a promising alternative route to energy-intensive industrial gas separation processes. Conventional microporous membranes often exhibit low gas selectivities for gases with similar kinetic diameters, primarily due to large pore sizes and reliance on Knudsen selectivity. In this study, we present self-assembled gold nanoparticle (Au NP) membranes that enable molecular gas separation within the kinetic diameter range of small gases such as H₂, CO₂, and O₂. By grafting silane molecules of varying sizes onto NP ligands, the gas selectivity of these membranes becomes tunable. This strategy achieves remarkably high gas selectivities of 192 and 35 for H₂/CO₂ and CO₂/O₂ gas pairs. Moreover, the Au NP membrane demonstrates a mixed gas selectivity of up to 30 for H₂/CO₂ even at room temperature, establishing its potential as a novel class of gas separation membranes with high and tunable selectivity.