Efficient molecular sieving separation of C2H2/CO2 by a flexible interpenetrated metal-organic framework

The efficient separation of C 2 H 2 /CO 2 mixtures is critical yet and remains challenging owing to their closely similar physical properties and molecular sizes. Herein, we report a novel flexible microporous adsorbent, Zn-SDBA-bpy (SDBA=4,4′-sulfonyldibenzoic acid, bpy = 4,4′-bipyridine), for molecular sieving of C 2 H 2 from CO 2 . Zn-SDBA-bpy features contracted interlayer cavities with a highly negative electro-environment arising from abundant exposed oxygen atoms of SDBA. Charge transfers between C 2 H 2 and the framework result in strong C 2 H 2 -host interactions that induce a selective gate-opening effect towards C 2 H 2 . Therefore, Zn-SDBA-bpy exhibits substantial C 2 H 2 capture at low pressure (20.7 cm 3 g −1 at 0.1 bar) while excluding CO 2 , demonstrating high C 2 H 2 /CO 2 selectivity (490.2). Notably, Zn-SDBA-bpy features the lowest C 2 H 2 gate-opening threshold ( ca. 0.01 bar) among reported flexible adsorbents for C 2 H 2 /CO 2 separation. Dynamic breakthrough experiments confirm its excellent C 2 H 2 /CO 2 separation yielding high-purity C 2 H 2 (>99.5 %) products. Modeling studies reveal the strong host-C 2 H 2 interactions and underlying mechanisms of molecular sieving within Zn-SDBA-bpy.