Surface engineering on a microporous metal–organic framework to boost ethane/ethylene separation under humid conditions

Recently, examples of metal–organic frameworks (MOFs) have been identified displaying ethane (C(2)H(6)) over ethylene (C(2)H(4)) adsorption selectivity. However, it remains a challenge to construct MOFs with both large C(2)H(6) adsorption capacity and high C(2)H(6)/C(2)H(4) adsorption selectivity, especially under humid conditions. Herein, we reported two isoreticular MOF-5 analogues (JNU-6 and JNU-6-CH(3)) and their potential applications in one-step separation of C(2)H(4) from C(2)H(6)/C(2)H(4) mixtures. The introduction of CH(3) groups not only reduces the pore size from 5.4 Å in JNU-6 to 4.1 Å in JNU-6-CH(3) but also renders an increased electron density on the pyrazolate N atoms of the organic linker. JNU-6-CH(3) retains its framework integrity even after being immersed in water for six months. More importantly, it exhibits large C(2)H(6) adsorption capacity (4.63 mmol g(−1)) and high C(2)H(6)/C(2)H(4) adsorption selectivity (1.67) due to the optimized pore size and surface function. Breakthrough experiments on JNU-6-CH(3) demonstrate that C(2)H(4) can be directly separated from C(2)H(6)/C(2)H(4) (50/50, v/v) mixtures, affording benchmark productivity of 22.06 and 18.71 L kg(−1) of high-purity C(2)H(4) (≥99.95%) under dry and humid conditions, respectively.