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

Abstract

Removing CO2 from crude syngas via physical adsorption is an effective method to yield eligible syngas. However, the bottleneck in trapping ppm‐level CO2 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 Mg2(dobdc) (1 a) and aminopyrazine (apz), which not only affords an ultra‐high CO2 capacity (145.0/197.6 cm3 g−1 (0.01/0.1 bar) at 298 K) but also produces ultra‐pure CO (purity ≥99.99 %) at a practical ambient temperature (TA). 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 CO2 from 1/99 CO2/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 H2/N2/CH4/CO/CO2 (46/18.3/2.4/32.3/1, v/v/v/v/v).

Binding of carbon dioxide and acetylene to free carboxylic acid sites in a metal–organic framework

“…The pressure under which structural transformation occurs is unique for each adsorbent, and thus excellent separation performance and selective uptake of target molecules can be achieved. 28,29 The adsorption selectivity of MFM-303(Al) for equimolar binary mixtures was estimated using ideal adsorbed solution theory (IAST) based upon single-component isotherms. 30,31 Interestingly, MFM-303(Al) exhibits an excellent IAST selectivity of 15.0 for C 2 H 2 over C 2 H 4 at 1 bar and 293 K (Fig.…”

“…The pressure under which structural transformation occurs is unique for each adsorbent, and thus excellent separation performance and selective uptake of target molecules can be achieved. 28,29…”