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

The efficient separation of fluorocarbon mixtures, such as perfluoropropene (C3F6) and perfluoropropane (C3F8), 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 C3F6 and C3F8 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 C3F8, interconnected by larger cavities that serve as diffusion highways for C3F6. Consequently, NCU-542 exhibits a high C3F6/C3F8 uptake ratio of 65.6 and a high C3F6 capacity of 52.5 cm3 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 C3F6 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 C3F6 and C3F8 separation.