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.