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Title: Phase transitions in zeolitic imidazolate framework 7: The importance of framework flexibility and guest-induced instability
Authors: Zhao, P
Lampronti, G.I
Lloyd, G.O
Wharmby, M.T
Facq, S
Cheetham, A.K 
Redfern, S.A.T
Keywords: Differential scanning calorimetry
Scanning electron microscopy
Thermogravimetric analysis
X ray powder diffraction
Framework flexibility
Lattice modes
Poor crystallinity
Raman bands
Solvent molecules
Temperature range
Vibrational modes
Zeolitic imidazolate frameworks
Organic solvents
Issue Date: 2014
Publisher: American Chemical Society
Citation: Zhao, P, Lampronti, G.I, Lloyd, G.O, Wharmby, M.T, Facq, S, Cheetham, A.K, Redfern, S.A.T (2014). Phase transitions in zeolitic imidazolate framework 7: The importance of framework flexibility and guest-induced instability. Chemistry of Materials 26 (5) : 1767-1769. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: A study of the phase transitions in ZIF-7 (zeolitic imidazolate frameworks- (Zn(PhIm)2, PhIm = benzimidazolate)) as a function of guest occupancy and temperature was reported. Raman spectra of an as-synthesized sample were collected in air between 297 and 421 K. The major contributions of the spectra come from the vibrational modes of the benzimidazolate ligand. Upon heating, most of the Raman bands remain similar and keep the same frequencies until 357 K, indicating that the structure of ZIF-7 seems to be stable in this temperature range. Above 357 K, strong modifications are observed in the regions corresponding to the lattice modes. The formation of ZIF-7-II is attributed to the loss of dimethylformamide (DMF) solvent molecules from the ZIF-7-I framework. This can be confirmed by the differential scanning calorimetry and thermogravimetric analysis traces of ZIF-7-I. The highly-distorted and locally-strained nature of ZIF-7-II leads to its poor crystallinity, reflected by X-ray powder diffraction and scanning electron microscope.
Source Title: Chemistry of Materials
ISSN: 0897-4756
DOI: 10.1021/cm500407f
Rights: Attribution 4.0 International
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