Cuprous/Vanadium Sites on MIL-101 for Selective CO Adsorption from Gas Mixtures with Superior Stability

For practical applications Cu(I) π-complexation adsorption demands both a high performance and a good stability. In this work, we simultaneously incorporated copper and vanadium into a typical metal-organic framework (MOF) of MIL-101. Thanks to the assistance of V, selective reduction of Cu(II) to Cu(I) was efficiently realized at a low temperature of 250 °C. Compared with the common reduction temperature of over 450 °C, the temperature in this work was dramatically reduced. The low temperature can guarantee the structural integrity of the MIL-101 support during the reduction procedure, since the structure of MIL-101 will collapse at or over 300 °C. We also demonstrated that the resulting CuVM adsorbents exhibited superior performances to those of pristine MIL-101 on CO separation from N₂ and H₂ mixtures, in terms of both the capacity and the selectivity. The utmost capacity of 29.2 cm³·g^-1 at 100 kPa for CO adsorption was achieved on 2.5CuVM, which significantly surpassed the capacity on MIL-101 (12.2 cm³·g^-1). With regards to the selectivity, 2.5CuVM showed a much better performance than MIL-101 as well, with that of 70.1 for CO/N₂ and 641.7 for CO/H₂. Moreover, in traditional π-complexation adsorbents, Cu(I) was easily oxidized to Cu(II) and thus lost the activity. In this study, the cuprous sites on 2.5CuVM material showed a remarkable oxygen-resistant ability under exposure to atmospheric air for about 2 weeks. This study provides a new avenue for the design and fabrication of Cu(I) π-complexation adsorbents with both high performances and excellent oxygen resistance.