Induced‐Fit‐Identification in a Rigid Metal‐Organic Framework for ppm‐Level CO2 Removal and Ultra‐Pure CO Enrichment

Abstract Removing CO 2 from crude syngas via physical adsorption is an effective method to yield eligible syngas. However, the bottleneck in trapping ppm‐level CO 2 and improving CO purity at higher working temperatures are major challenges. Here we report a thermoresponsive metal–organic framework ( 1 a‐apz ), assembled by rigid Mg 2 (dobdc) ( 1 a ) and aminopyrazine (apz), which not only affords an ultra‐high CO 2 capacity (145.0/197.6 cm 3 g −1 (0.01/0.1 bar) at 298 K) but also produces ultra‐pure CO (purity ≥99.99 %) at a practical ambient temperature ( T A ). Several characterization results, including variable‐temperature tests, in situ high‐resolution synchrotron X‐ray diffraction (HR‐SXRD), and simulations, explicitly unravel that the excellent property is attributed to the induced‐fit‐identification in 1 a‐apz that comprises self‐adaption of apz, multiple binding sites, and complementary electrostatic potential (ESP). Breakthrough tests suggest that 1 a‐apz can remove CO 2 from 1/99 CO 2 /CO mixtures at practical 348 K, yielding 70.5 L kg −1 of CO with ultra‐high purity of ≥99.99 %. The excellent separation performance is also revealed by separating crude syngas that contains quinary mixtures of H 2 /N 2 /CH 4 /CO/CO 2 (46/18.3/2.4/32.3/1, v/v/v/v/v).