Robust carbazole-based covalent triazine frameworks with defective ultramicropore structure for efficient ethane-selective ethane-ethylene separation.

[Display omitted] • CTF-DCTC-500 with defective ultramicropore was prepared. • CTF-DCTC-500 possesses excellent chemical stability in harsh conditions. • The introduction of defective ultramicropore enhanced the C 2 H 6 uptake of CTF. • The C 2 H 6 /C 2 H 4 selectivity in CTF-DCTC-500 exceeds all reported COF. • CTF-DCTC-500 can obtain polymer-grade C 2 H 4 in actual C 2 H 6 /C 2 H 4 separation. The selective adsorption of ethane (C 2 H 6) in the separation process of C 2 H 6 and ethylene (C 2 H 4) is of great importance for obtaining polymer-grade C 2 H 4 in industry, yet it is still challenging task to develop suitable adsorbents with large adsorption capacity, high selectivity and excellent stability for efficient separation of C 2 H 6 /C 2 H 4. Herein, carbazole-based covalent trazine frameworks (CTFs) prepared by ionothermal strategy are proposed for C 2 H 6 /C 2 H 4 for the first time. By changing the preparation conditions, the obtained CTF-DCTC-500 shows defective ultramicropore structure while CTF-DCTC-400 does not. Compared with CTF-DCTC-400, the introduction of defective ultramicropore in CTF-DCTC-500 not only increases the adsorption capacity of C 2 H 6 , but also exhibits obviously C 2 H 6 /C 2 H 4 separation behavior. Surprisingly, the adsorption selectivity of C 2 H 6 /C 2 H 4 in CTF-DCTC-500 at 298 K and 1 bar is up to 2.08, exceeding all reported COF materials. To the best of our knowledge, this is first reported CTF material with preferential C 2 H 6 adsorption over C 2 H 4. Breakthrough experiments on CTF-DCTC-500 reveal that the polymer-grade C 2 H 4 with 99.95 % purity can be directly obtained from the C 2 H 6 /C 2 H 4 mixture in the practical application. Furthermore, CTF-DCTC-500 possesses the high chemical stability and excellent cycling stability and regeneration for C 2 H 6 /C 2 H 4 separation, indicating it is a promising material for C 2 H 6 /C 2 H 4 separation. This work not only provides a highly stable carbazole-based CTF with high C 2 H 6 /C 2 H 4 separation selectivity, but also emphasizes the important role of defective ultramicropore structure on C 2 H 6 /C 2 H 4 separation. [ABSTRACT FROM AUTHOR]