To design such systems for CO purification, the affinity between the metal and CO is a central point of consideration (Fig. ). In principle, more rapid and selective adsorption of CO can be achieved by the introduction of low-(or zero-) valent, d-electron-rich metals, as such metals can form thermodynamically favorable metal-CO interactions through their stronger metal-to-CO -backdonation compared to higher-valent metals . However, the strong interaction between low-valent metals and CO greatly affects the desorption efficiency. In fact, the reversible chemisorption of CO with zero-valent transition metals has been achieved under the extreme conditions used in the Mond process (vide supra). Thus, hitherto reported adsorption technologies have predominantly relied on the chemisorption of CO by higher-valent metals to minimize the influence of metal-to-CO -backdonation. Temperature-swing operations, i.e., the use of a higher operation temperature during CO desorption than during CO adsorption, are frequently applied, and desorption is often carried out under reduced pressure (pressure-swing operation) . Against this background, we envisioned the development of a process for the reversible chemisorption of CO using a zero-valent transition metal that could potentially exhibit strong metal-to-CO -backdonation to showcase a novel strategy for the controlled purification and long-term storage of CO.