Low‐Concentration C 2 H 6 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 C 2 H 6 interaction and large C 2 H 6 uptake at low‐concentration level has rarely been reported, due to the large p K a value and small quadrupole moment of C 2 H 6 . 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‐MOF 2 ), which enables the record‐breaking performance for low concentration C 2 H 6 capture. IISERP‐MOF 2 exhibits the large C 2 H 6 adsorption enthalpy of 56.7 kJ/mol, and record‐high C 2 H 6 uptake at low pressure of 0.01–0.1 bar and 298 K (1.8 mmol/g at 0.01 bar). Molecule simulations and C 2 H 6 ‐loading crystal structure analysis revealed that the maximized interaction sites in IISERP‐MOF 2 with ethane molecule originates the strong C 2 H 6 adsorption. The dynamic breakthrough experiments for gas mixtures of C 2 H 6 /N 2 (1/999, v / v ) and C 2 H 6 /CH 4 (5/95, v / v ) proved the excellent low‐concentration C 2 H 6 capture performance.