High‐Pressure Molecular Sieving of High‐Humidity C₂H₄/C₂H₆ Mixture by a Hydrophobic Flexible Metal–Organic Framework

Abstract

Abstract Molecular sieving is an ideal separation mechanism, but controlling pore size, restricting framework flexibility, and avoiding strong adsorption are all very challenging. Here, we report a flexible adsorbent showing molecular sieving at ambient temperature and high pressure, even under high humidity. While typical guest‐induced transformations are observed, a high transition pressure of 16.6 atm is observed for C 2 H 4 at 298 K because of very weak C 2 H 4 adsorption (~16 kJ mol −1 ). Also, C 2 H 6 is completely excluded below the pore‐opening pressure of 7.7 atm, giving single‐component selectivity of ca. 300. Quantitative high‐pressure column breakthrough experiments using 1 : 1 C 2 H 4 /C 2 H 6 mixtures at 10 atm as input confirm molecular sieving with C 2 H 4 adsorption of 0.73 mmol g −1 or 32 cm 3 (STP) cm −3 and negligible C 2 H 6 adsorption of 0.001(2) mmol g −1 , and the adsorbent can be completely regenerated by inert gas purging. Furthermore, it is highly hydrophobic with negligible water adsorption, and the C 2 H 4 /C 2 H 6 separation performance is unaffected at high humidity.