Fine-Tuning Microporosity of Crystalline Vanadomolybdate\nFrameworks for Selective Adsorptive Separation of Kr from Xe

Selective\nadsorptive capture and separation of chemically inert\nkrypton (Kr) and xenon (Xe) noble gases with very low ppmv concentrations\nin air and industrial off-gases constitute an important technological\nchallenge. Here, using a synergistic combination of experiment and\ntheory, the microporous crystalline vanadomolybdates (MoVO<sub><i>x</i></sub>) as highly selective Kr sorbents are studied in\ndetail. By varying the Mo/V ratios, we show for the first time that\ntheir one-dimensional (1D) pores can be fine-tuned for the size-selective\nadsorption of Kr over the larger Xe with selectivities reaching >100.\nUsing extensive electronic structure calculations and grand canonical\nMonte Carlo simulations, the competition between Kr uptake with CO<sub>2</sub> and N<sub>2</sub> was also investigated. As most materials\nreported so far are selective toward the larger, more polarizable\nXe than Kr, this work constitutes an important step toward robust\nKr-selective sorbent materials. This work highlights the potential\nuse of porous crystalline transition metal oxides as energy-efficient\nand selective noble gas capture sorbents for industrial applications.