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Extreme Flexibility in a Zeolitic Imidazolate Framework: Porous to Dense Phase Transition in Desolvated ZIF‐4 |
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| Authors: | Dr. Michael T. Wharmby Dr. Sebastian Henke Dr. Thomas D. Bennett Dr. Sneha R. Bajpe Inke Schwedler Dr. Stephen P. Thompson Dr. Fabia Gozzo Dr. Petra Simoncic Dr. Caroline Mellot‐Draznieks Prof. Haizheng Tao Prof. Yuanzheng Yue Prof. Anthony K. Cheetham |
| Affiliation: | 1. Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS (UK);2. Diamond Light Source Ltd. Diamond House, Harwell Science & Innovation Campus, Didcot, Oxfordshire, OX11 0DE (UK);3. Paul Scherrer Institut, 5232 Villigen PSI (Switzerland);4. CNRS UMR 8229, Sorbonne Universités, UPMC Univ Paris 06, Collège de France, 11 Place Marcelin Berthelot, 75005 Paris Cedex 05 (France);5. State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China);6. Section of Chemistry, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg (Denmark) |
| Abstract: | Desolvated zeolitic imidazolate framework ZIF‐4(Zn) undergoes a discontinuous porous to dense phase transition on cooling through 140 K, with a 23 % contraction in unit cell volume. The structure of the non‐porous, low temperature phase was determined from synchrotron X‐ray powder diffraction data and its density was found to be slightly less than that of the densest ZIF phase, ZIF‐zni. The mechanism of the phase transition involves a cooperative rotation of imidazolate linkers resulting in isotropic framework contraction and pore space minimization. DFT calculations established the energy of the new structure relative to those of the room temperature phase and ZIF‐zni, while DSC measurements indicate the entropic stabilization of the porous room temperature phase at temperatures above 140 K. |
| Keywords: | imidazolates metal– organic frameworks phase transitions porosity zeolitic imidazolate frameworks |