Tuning Pore Polarization to Boost Ethane/Ethylene Separation Performance in Hydrogen‐Bonded Organic Frameworks
Yunzhe Zhou, Cheng Chen, Rajamani Krishna, Zhenyu Ji, Daqiang Yuan, Mingyan Wu
Abstract
Abstract Hydrogen‐bonded organic frameworks (HOFs) show great potential in energy‐saving C 2 H 6 /C 2 H 4 separation, but there are few examples of one‐step acquisition of C 2 H 4 from C 2 H 6 /C 2 H 4 because it is still difficult to achieve the reverse‐order adsorption of C 2 H 6 and C 2 H 4 . In this work, we boost the C 2 H 6 /C 2 H 4 separation performance in two graphene‐sheet‐like HOFs by tuning pore polarization. Upon heating, an in situ solid phase transformation can be observed from HOF‐NBDA(DMA) (DMA=dimethylamine cation) to HOF‐NBDA , accompanied with transformation of the electronegative skeleton into neutral one. As a result, the pore surface of HOF‐NBDA has become nonpolar, which is beneficial to selectively adsorbing C 2 H 6 . The difference in the capacities for C 2 H 6 and C 2 H 4 is 23.4 cm 3 g −1 for HOF‐NBDA , and the C 2 H 6 /C 2 H 4 uptake ratio is 136 %, which are much higher than those for HOF‐NBDA(DMA) (5.0 cm 3 g −1 and 108 % respectively). Practical breakthrough experiments demonstrate HOF‐NBDA could produce polymer‐grade C 2 H 4 from C 2 H 6 /C 2 H 4 (1/99, v/v) mixture with a high productivity of 29.2 L kg −1 at 298 K, which is about five times as high as HOF‐NBDA(DMA) (5.4 L kg −1 ). In addition, in situ breakthrough experiments and theoretical calculations indicate the pore surface of HOF‐NBDA is beneficial to preferentially capture C 2 H 6 and thus boosts selective separation of C 2 H 6 /C 2 H 4 .