title: Extreme Flexibility in a Zeolitic Imidazolate Framework: Porous to Dense Phase Transition in Desolvated ZIF-4.
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.
authors: Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS (UK).|Diamond Light Source Ltd. Diamond House, Harwell Science & Innovation Campus, Didcot, Oxfordshire, OX11 0DE (UK).
authors: Michael T
authors: MT
authors: Wharmby
authors: Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS (UK).
authors: Sebastian
authors: S
authors: Henke
authors: Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS (UK).
authors: Thomas D
authors: TD
authors: Bennett
authors: Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS (UK).
authors: Sneha R
authors: SR
authors: Bajpe
authors: Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS (UK).
authors: Inke
authors: I
authors: Schwedler
authors: Diamond Light Source Ltd. Diamond House, Harwell Science & Innovation Campus, Didcot, Oxfordshire, OX11 0DE (UK).
authors: Stephen P
authors: SP
authors: Thompson
authors: Paul Scherrer Institut, 5232 Villigen PSI (Switzerland).
authors: Fabia
authors: F
authors: Gozzo
authors: Paul Scherrer Institut, 5232 Villigen PSI (Switzerland).
authors: Petra
authors: P
authors: Simoncic
authors: CNRS UMR 8229, Sorbonne Universités, UPMC Univ Paris 06, Collège de France, 11 Place Marcelin Berthelot, 75005 Paris Cedex 05 (France).
authors: Caroline
authors: C
authors: Mellot-Draznieks
authors: State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China).
authors: Haizheng
authors: H
authors: Tao
authors: State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China).|Section of Chemistry, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg (Denmark).
authors: Yuanzheng
authors: Y
authors: Yue
authors: Department of Materials Science & Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge, CB3 0FS (UK). akc30@cam.ac.uk.
authors: Anthony K
authors: AK
authors: Cheetham
keywords: imidazolates; metal-organic frameworks; phase transitions; porosity; zeolitic imidazolate frameworks