A High‐Capacity Molecular Sieve With Ultrafast Adsorption Kinetics for Separating C ₃ F ₆ /C ₃ F ₈

ABSTRACT The efficient separation of fluorocarbon mixtures, such as perfluoropropene (C 3 F 6 ) and perfluoropropane (C 3 F 8 ), is critical for producing high‐purity electronic gases, but remains a formidable challenge due to their similarity in physicochemical characteristics. Herein, we report the size‐sieving separation of C 3 F 6 and C 3 F 8 by a robust zinc‐based metal–organic framework, NCU‐542, which features a “dual‐channel bottleneck‐cavity” pore architecture. We show that its specific pore geometry and optimal pore dimensions are beneficial to overcome the intrinsic trade‐off between size‐sieving precision and diffusion efficiency. The framework contains narrow sieving necks (∼5.2 Å) that fully exclude bulky C 3 F 8 , interconnected by larger cavities that serve as diffusion highways for C 3 F 6 . Consequently, NCU‐542 exhibits a high C 3 F 6 /C 3 F 8 uptake ratio of 65.6 and a high C 3 F 6 capacity of 52.5 cm 3 g −1 at 298 K and 1 bar, while achieving ultrafast adsorption kinetics. In situ IR spectroscopy and DFT calculations elucidate that the specific recognition of C 3 F 6 is driven by multiple cooperative C−H···F interactions at the imidazolate‐zinc junctions. Furthermore, the shaped pellets of NCU‐542 retain excellent structural integrity and separation performance, validating its industrial potential for C 3 F 6 and C 3 F 8 separation.