(155b) Xenon Trapping in Silica Nanocages Supported on Ru(0001)

Xenon is a valuable and scarce noble gas used in various applications, including lighting, electronics, and anesthetics, among many others. It is also a volatile byproduct of the nuclear fission of uranium. Prior studies on two-dimensional silica and aluminosilicate crystalline bilayers grown on metal supports showed that these structures could trap all noble gases larger than Ne irreversibly at room temperature. The gases could then be selectively released by heating the materials to different temperatures depending on the gas under study. However, the synthesis of such silicate bilayers is prohibitively expensive and time-consuming for practical purposes. Since the hexagonal prism silicate nanocage in contact with a metal was found responsible for the trapping, we hypothesize that an alternative structure having those building blocks could then be used. We then used the commercially available and relatively inexpensive molecule dodecaphenyl-polyhedral oligomeric silsesquioxane (Dodecaphenyl-POSS) to produce a material using POSS molecules supported on a thin ruthenium film to explore its behavior toward Xe trapping. We use synchrotron-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to follow the Xe trapping inside. Xe release occurs only by heating to temperatures above 750 K. Monte Carlo simulations are used to model the trapping kinetics. Density functional theory calculations show consistent activation energies for Xe exiting the cages. The material and strategy applied are expected to also work for Ar, Kr, and Rn.