Carbon monoxide (CO) is an essential feedstock that is widely used in the synthesis of commodity chemicals such as alcohols, carboxylic acids, and polycarbonates . CO has also been used for metal-refining processes, e.g., the Mond process, which consists of the carbonylation of crude Ni(0) at around 50 °C and thermolysis of gaseous Ni(CO)4 at 180-280 °C . Huge amounts of high-purity CO are thus produced during the removal of contaminants such as H2, N2, CO2, and CH4 from crude materials obtained from the gasification processes of hydrocarbon resources and the steel production industry . In these cases, cryogenic distillation technology is typically applied for CO purification, although technologies based on adsorption, absorption, and membranes have also been explored intensively . In terms of the purity of the produced CO, repeatable adsorption/desorption sequences based on the coordination/dissociation of CO on metal ions such as Fe(II) , Co(II) , Ni(II) , Cu(I) , Cu(II) , and Ir(III) incorporated in solid-state adsorbents have shown exceptional results (Fig. ). For example, Kirschner et al. reported the use of the crystalline solid of a Fe(II)-carbonyl complex that bears a PNP pincer-type ligand for the reversible chemisorption of CO . In this reaction, the adsorption proceeded smoothly under ambient conditions, while the efficient desorption required heating (100 °C) under reduced pressure. The crystalline coordination polymers known as metal-organic frameworks (MOFs) have also been used for the purification of CO . Matsuda and Kitagawa et al. demonstrated the separation of CO from a gaseous mixture including nitrogen (N2), which is the most competitive gas for CO in physisorption-based separation processes due to its similar molecular size, using a Cu(II)-based nanoporous crystalline material; this separation was enabled by the coordination of CO to Cu(II) ions under cryogenic conditions . In this report, desorption was carried out by raising the temperature to 27 °C in a closed system that had undergone a single degassing cycle. Similarly, Long et al. proposed the application of Fe(II)-, Co(II)-, and Ni(II)based MOFs for the purification of CO based on their high susceptibility to adsorb CO .