Dynamic molecular pockets on one-dimensional channels for splitting ethylene from C2–C4 alkynes

Abstract

Molecular sieving adsorbents can offer maximum adsorption selectivity with respect to molecular sizes, yet it is still challenging to discriminate middle-sized molecules from a mixture of three or more components. Here we report a metal–organic framework (JNU-3a) with dynamic molecular pockets along one-dimensional channels, enabling the one-step removal of ethylene (C2H4) from mixtures with C2–C4 alkynes in a single adsorption step regardless of their molecular sizes. Laboratory-scale column breakthrough experiments on 1.4 g of JNU-3a reveal that the three alkynes break through the column at almost the same but a later time, resulting in the high-purity separation of C2H4 (≥99.9995%) from a mixture with C2–C4 alkynes in a single adsorption operation. We further demonstrate pilot-scale column breakthrough on 107 g of JNU-3a and the collection of C2H4 in a gas cylinder. In particular, 30 continuous runs for a C2H2/C3H4/1-C4H6/C2H4 mixture (1:1:1:97) afford an average of 76.1 g per cycle of high-purity C2H4. Overall, JNU-3a may have great potential for industrial C2H4 purification via the concurrent removal of C2–C4 alkynes. It is challenging to separate middle-sized molecules from complex mixtures using traditional molecular sieves. Here a metal–organic framework has been developed with dynamic molecular pockets that can adjust and accommodate alkynes preferentially, realizing efficient production of high-purity ethylene from its mixtures with alkynes regardless of their molecular sizes.