Stepwise customizing pore environments of C2H2-selective frameworks for one-step C2H4 acquisition from ternary mixtures

Abstract

One-step purification of C2H4 from ternary C2H2/C2H4/C2H6 mixture is crucial but challenging since the primary physical properties of C2H4 all fall between C2H2 and C2H6. Hence, we report an effective approach for purifying C2H4 through stepwise customizing pore environments on C2H2-selective materials. Utilizing SIFSIX-1-Cu as a prototype material, we incorporated one or two methoxyl groups onto 4,4′-bipyridine to obtain isomorphic framework SIFSIX-1-Cu-OMe and SIFSIX-1-Cu-(OMe)2 respectively. As expected, pore sizes gradually decrease, while C2H6 binding sites increase. Ultimately, the C2H6/C2H4 (10/90) selectivity gradually increases from 1.18 (SIFSIX-1-Cu) to 1.27 (SIFSIX-1-Cu-OMe) and finally to a remarkably high value of 1.79 (SIFSIX-1-Cu-(OMe)2). As anticipated, SIFSIX-1-Cu-(OMe)2 can achieve one-step acquisition of polymer-grade C2H4 (≥99.95 %) from C2H2/C2H4/C2H6 (1/90/9) mixture with high productivity of 6.82 L/kg. Furthermore, theoretical calculations indicate that the pore surface of SIFSIX-1-Cu-(OMe)2 is beneficial to preferentially capture C2H2 and C2H6, and thus realizes one-step purification of C2H4.