A Microporous Metal‐Organic Framework with Channels Constructed from Nonpolar Aromatic Rings for the Selective Separation of Ethane/Ethylene Mixtures

Abstract

The separation of ethane and ethylene is an important segment in the purification of chemical raw materials in industrial production. However, due to their similar physical and chemical properties, the separation of C2H6/C2H4 is challenging. Herein, we report the selective adsorption of ethane over ethylene by a microporous metal‐organic framework with nonpolar aromatic rings constructed channels, [Co1.5(TATB)(H2O)0.5] ⋅ 5DMA ⋅ 3H2O (Co‐TATB, H3TATB=4,4’,4’’‐(s‐triazine‐2,4,6‐triyl) tribenzoic acid). This compound showed a higher ethane capacity than that of ethylene, and a low adsorption enthalpy of ethane only of 19.4 kJ mol−1. Further, the dynamic breakthrough experimental confirmed that Co‐TATB can selectively adsorb ethane from ethane/ethylene separation.

A pacs-type metal–organic framework with high adsorption capacity for inverse C2H6/C2H4 separation

“…18 However, for these C 2 H 4 -selective MOFs, the co-adsorbed C 2 H 6 impurity could be substantially removed only after multiple energy-intensive adsorption-desorption cycles. [19][20][21][22] In comparison, the recently discovered C 2 H 6 -selective [23][24][25][26] MOFs are more preferred in energy efficiency, because they are capable of separating C 2 H 4 from binary C 2 H 4 /C 2 H 6 mixtures in one adsorption step. For MOFs, the way to accessing the non-trivial inverse adsorption of C 2 H 6 over C 2 H 4 is through constructing their pore surfaces by linking coordinatively saturated metal sites (i.e., without open metal sites) with aromatic rings or aliphatic chains.…”

Combination of Low-Polar and Polar Binding Sites in Aliphatic MOFs for the Efficient C2H6/C2H4 Separation

“…Most of them showed an adsorption preference of C 2 H 4 from the C 2 H 4 /C 2 H 6 mixture due to the larger quadrupole moment (1.50 × 10 –26 esu cm 2 for C 2 H 4 ; 0.65 × 10 –26 esu cm 2 for C 2 H 6 ) and more π electrons of C 2 H 4 that enabled the stronger interactions between the C 2 H 4 molecule and the open metal sites or highly polar groups on the adsorbent pore surface. − However, their similar molecular size tends to result in co-adsorption phenomenon, seriously reducing the product purity of C 2 H 4 . Even for those adsorbents that realized molecule exclusion of C 2 H 6 , , a large quantity of the adsorbent will be needed on account of the high concentration of C 2 H 4 (usually >95%, v/v) in the mixture, and an additional desorption process is required to get the C 2 H 4 product from C 2 H 4 -loaded adsorbents, increasing the energy consumption and complicating the separation process. − Therefore, it is extremely urgent and necessary to construct new C 2 H 6 -preferring adsorbents to realize an efficient one-step purification of C 2 H 4 .…”