From pure experimental isotherms and ideal adsorbed solution theory (IAST), we confirmed a recent report that Co-MOF-74 provides the highest Xe uptake as well as the highest Xe/Kr selectivity among the three M-MOF-74 series (M = Co, Mg, and Zn). From breakthrough experiments, we then showed the first demonstration of the potential of Co-MOF-74 for Xe/Kr separations under mixture flow conditions. Remarkably, the experimental breakthrough curves for three consecutive cycles are essentially unchanged even if the column was regenerated under helium flows at room temperature between each cycle. Isosteric heat of adsorption (Qst) for Xe, adsorbed Xe molecules per metal, and binding strengths and electronic density of states (DOS) analyses from first principles calculations all indicate that unsaturated Co2+ sites attract Xe more strongly than do unsaturated Mg2+ and Zn2+ sites. The DOS analyses show that the d orbital of the Co2+ is the main contributors for the strong interaction. These results suggest that Co-MOF-74 is a promising adsorbent for separations of Xe and Kr.
Bibliographical noteFunding Information:
This work was supported by In-house Research and Development Program of the Korea Institute of Energy Research (KIER) ( B6-2441 ). Also, this work was supported by the Technology Innovation Program ( 10048649 ) funded by the Ministry of Trade, Industry and Energy (MI, Korea).
© 2016 Elsevier Inc.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials