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.