Scalable reflux synthesis of a bimicroporous hydrogen-bonded framework with specific molecule recognition ability for one-step ethylene purification

Abstract

Efficient purification of ethylene (C₂H₄) from an acetylene/ethylene/ethane (C₂H₂/C₂H₄/C₂H₆) mixture is crucial but challenging. For this purpose, herein, an ideal separation process that employed an adsorbent with specific adsorption regions for guest molecules and multiple hydrogen-bonds (H-bonds) was proposed. A penetrated cage-channel bimicroporous hydrogen-bonded organic framework (SNNU-520) was selected to verify the feasibility of this approach. Owing to the size effect, the small size cage located in the metal–organic building units allowed only C₂H₂ trapping, and the penetrated channel with medium approachable size mainly contributed to the adsorption of C₂H₄ and C₂H₆ molecules. Together with the multiple H-bond interactions, the penetrated channel preferred the C₂H₆ molecules. Furthermore, thermodynamic and kinetic adsorption experiments and theoretical simulation were conducted to confirm the adsorption mechanism. According to the results, SNNU-520 exhibited an exceptionally high C₂H₂ and C₂H₆ uptake capacity, and the C₂H₆ uptake at 298 K was at a superior level among most of the reported HOFs and MOFs for ternary mixture separation. Dynamic breakthrough experiments showed that SNNU-520 could produce highly purified C₂H₄ from a C₂H₄/C₂H₆ mixture and C₂H₂/C₂H₄/C₂H₆ ternary mixture in one step with a moderately high productivity, implying that the trade-off effect between the adsorption capacity and selectivity was also overcome. Thus, considering its scalable reflux synthesis process, extra-high stability, unique and adjustable penetrated cage-channels, and abundant H-bonds, SNNU-520 is a potential material for industrial applications.