Room-Temperature Noble Gas Trapping in Silica Nanocages on Metal Substrates

The separation and purification of noble gases is challenging due to their chemical inertness, requiring cryogenic conditions. A promising room-temperature alternative involves capturing noble gases within metal-supported silica nanocages through physical confinement and electronic interactions (Xu et al., Small, 2021). In this mechanism, ionized noble gas enters a nanocage and is neutralized via electron donation from the metal, rendering escape energetically unfavorable. Here we present the longevity of noble gas capture for Ar and Xe as a function of metal support material and silica nanocage size. Near-monolayer films of cubic or hexagonal prism cages were deposited with a Langmuir trough onto metal single-crystals, Ag(111), Au(111), and Ru(0001). The nanocage/metal samples were then calcined, reduced in hydrogen, exposed to a noble gas plasma, and analyzed with X-ray photoelectron spectroscopy (XPS) to quantify noble gas capture. Hexagonal-prism cages retained Xe on all three metals, with persistence for at least 12 hours at room temperature. Cubic cages excluded the larger Xe atoms, but trapped the Ar, showing selectivity dependent on cage size and atom size. These findings pave the way for cost-effective and selective noble gas separation.