Size-inverse molecular sieving xenon/krypton separation through cation-tuned gating effect within Linde Type A zeolites.

Abstract

Achieving highly selective xenon/krypton separation is a longstanding challenge due to the similar physicochemical properties of these noble gases. Here, we develop the cation-tuned gating sieving mechanism in Linde Type A zeolites to achieve a high xenon/krypton IAST selectivity over 1600. Through the cation exchange by Ag⁺ to introduce the preferential binding of xenon over krypton gas, followed by Ca²⁺ exchange to modulate cation density within the pore cavity so as to facilitate xenon uptake, the resulting Ag₉Ca_1.5A overcomes the kinetic limitations and achieves a dynamic xenon/krypton selectivity of 30 - the highest reported in the open literature - along with a high dynamic xenon uptake of 1.65 mmol/g. In this work, the sieving separation mechanism is exclusively established by the combined isothermal adsorption measurements, breakthrough experiments, synchrotron powder X-ray diffraction, X-ray absorption spectra, and ab initio density functional theory calculations.