Low-Concentration C2 H6 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 C2 H6 interaction and large C2 H6 uptake at low-concentration level has rarely been reported, due to the large pKa value and small quadrupole moment of C2 H6 . 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 C2 H6 capture. IISERP-MOF2 exhibits the large C2 H6 adsorption enthalpy of 56.7 kJ/mol, and record-high C2 H6 uptake at low pressure of 0.01-0.1 bar and 298 K (1.8 mmol/g at 0.01 bar). Molecule simulations and C2 H6 -loading crystal structure analysis revealed that the maximized interaction sites in IISERP-MOF2 with ethane molecule originates the strong C2 H6 adsorption. The dynamic breakthrough experiments for gas mixtures of C2 H6 /N2 (1/999, v/v) and C2 H6 /CH4 (5/95, v/v) proved the excellent low-concentration C2 H6 capture performance.