  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.
