Carbon monoxide is an important component in gas mixtures both as an impurity or as potential chemical feedstock. The application of CO-selective adsorbents to concentrate CO from gas mixtures is well established and includes publications on solid-gas contactors and liquid-gas contactors. More recently, the use of CO-selective adsorbents for the removal of CO from H2 feeds to fuel cell applications is of growing interest due to the stringent CO specifications from PEM fuel cell manufacturers. The design of CO-selective adsorbents for Rapid Cycle PSA carries with it a specific set of requirements to take full advantage of the process intensification but also allows for the exploitation of solid-state reactions and powder-based processing in their preparation.