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