Low-Concentration C₂H₆ Capture Enabled by Size Matching in the Ultramicropore

Low-concentration ethane capture is crucial for environmental protection and natural gas purification. The ideal physisorbent with strong C₂H₆ interaction and large C₂H₆ uptake at low-concentration level has rarely been reported, due to the large pK_a value and small quadrupole moment of C₂H₆. Herein, we demonstrate the perfectly size matching between the ultramicropore (pore size of 4.6 Å) and ethane (kinetic diameter of 4.4 Å) in a nickel pyridine-4-carboxylate metal–organic framework (IISERP-MOF2), which enables the record-breaking performance for low concentration C₂H₆ capture. IISERP-MOF2 exhibits the large C₂H₆ adsorption enthalpy of 56.7 kJ/mol, and record-high C₂H₆ uptake at low pressure of 0.01–0.1 bar and 298 K (1.8 mmol/g at 0.01 bar). Molecule simulations and C₂H₆-loading crystal structure analysis revealed that the maximized interaction sites in IISERP-MOF2 with ethane molecule originates the strong C₂H₆ adsorption. The dynamic breakthrough experiments for gas mixtures of C₂H₆/N₂(1/999, v/v) and C₂H₆/CH₄ (5/95, v/v) proved the excellent low-concentration C₂H₆ capture performance.