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Updated: Jun 12, 2025

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes
Published on: August 16, 2018
Restricting Linker Rotation in Nanocages of ZIF-8 Membranes using Crown Ether "Molecular Locks" for Enhanced
Zinan Zhang1, Han Zhu1, Hua Jin1
1School of Materials Science and Chemical Engineering, Ningbo University, Ningbo, 315211, China.
Abstract:
ZIF-8 membranes have long been prized for their exceptional C3H6/C3H8 separation performance. On the other hand, ZIF-8 has structural flexibility, where the external pressure triggers channel expansion, potentially deteriorating the molecular sieving ability. Here, we demonstrate a reliable strategy to fine-tune the flexible pore structure of ZIF-8 by embedding crown ether within a ZIF-8 membrane. Benzo-15-crown-5 (15C5) was selected as the cavity occupant and perfectly confined in the sodalite (SOD) cage of ZIF-8. The 15C5 molecules, which have a size comparable to the nanocage, impose a spatial constraint on linker rotation, enabling the phase transition to a rigid structure in the flexible ZIF-8. The corresponding 15C5@ZIF-8 membranes achieve an ultrahigh C3H6/C3H8 selectivity of 220, outperforming that of most membranes. Unlike their flexible counterparts, the resulting membranes manifest a positive increase in the C3H6/C3H8 separation factor with elevated pressure, securing a record-high C3H6/C3H8 separation factor of 331 under 7 bar. More importantly, extraordinary separation stability was demonstrated with continuous measurement, which is highly desirable for practical applications.
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