To efficiently capture, activate, and transform small molecules, metalloenzymes have evolved to integrate a well-organized pocket around the active metal center. Within this cavity, second coordination sphere functionalities are precisely positioned to optimize the rate, selectivity, and energy cost of catalytic reactions. Inspired by this strategy, an artificial distal pocket defined by a preorganized 3D strap is introduced on an iron-porphyrin catalyst (sc-Fe) for the CO