Fine-tuning Microporosity of Crystalline Vanadomolybdate Frameworks for Selective Adsorptive Separation of Kr from Xe

TL;DR

This study demonstrates how to fine-tune microporous vanadomolybdate frameworks for highly selective krypton adsorption over xenon, using experimental and theoretical methods, advancing noble gas separation technology.

Contribution

First demonstration of size-selective Kr over Xe adsorption in vanadomolybdate frameworks by tuning pore sizes through Mo/V ratios, supported by computational analysis.

Findings

Selectivities >100 for Kr over Xe achieved.

Pore size tuning controls gas selectivity.

Potential for energy-efficient noble gas capture.

Abstract

Selective adsorptive capture and separation of chemically inert Kr and Xe noble gases with very low ppmv concentrations in air and industrial off-gases constitute an important technological challenge. Here, using a synergistic combination of experiment and theory, the microporous crystalline vanadomolybdates (MoVOx) as highly selective Kr sorbents are studied in detail. By varying the Mo/V ratios, we show for the first time that their one-dimensional pores can be fine-tuned for the size-selective adsorption of Kr over the larger Xe with selectivities reaching >100. Using extensive electronic structure calculations and grand canonical Monte-Carlo simulations, the competition between Kr uptake with CO2 and N2 was also investigated. As most materials reported so far are selective toward the larger, more polarizable Xe than Kr, this work constitutes an important step toward robust Kr-selective sorbent materials. This work highlights the potential use of porous crystalline transition metal oxides as energy-efficient and selective noble gas capture sorbents for industrial applications.