A novel microporous hydrogen-bonded framework with electron-rich alkynyl groups for highly efficient C2H6/C2H4 separation

Abstract

Microporous hydrogen-bonded organic frameworks (HOFs) have been considered as promising materials for ethane/ethylene (C2H6/C2H4) separation due to their native nonpolar pores. However, the absence of functional binding sites on the nonpolar pore surfaces commonly limits their separation performance. Herein, we report and construct a novel HOF material (termed as ZJU-HOF-60a) by incorporating electron-rich alkynyl groups into the pore surfaces to achieve highly efficient C2H6/C2H4 separation. The incorporated alkynyl groups can not only serve as functional binding sites to provide multiple supramolecular interactions with C2H6 molecule, but also do not take part in the formation of any hydrogen bonds so as to obtain the desired HOF framework. The alkynyl-functionalized ZJU-HOF-60a thus exhibits both the top-tier C2H6 uptake capacity of 3.79 mmol g−1 and C2H6/C2H4 uptake ratio of 1.58 at 296 K and 1 bar, surpassing most of the C2H6-selective HOFs ever reported. Theoretical calculations indicate that the incorporated alkynyl groups combined with the surrounding carboxylic groups provide stronger and more number of C−H···π and C−H···O interactions to bind with C2H6 over C2H4, thus accounting for the efficient C2H6/C2H4 separation. The actual separation performance of ZJU-HOF-60a was confirmed by breakthrough experiments for 50/50 (v/v) C2H6/C2H4 gas mixtures, affording a high pure C2H4 productivity of 7.8 L kg−1 at ambient conditions.