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Thermodynamic features and enthalpy relaxation in a metal–organic framework glass

DOI: 10.1039/C8CP02340A DOI Help

Authors: Chao Zhou (Aalborg University) , Malwina Stepniewska (Aalborg University) , Louis Longley (University of Cambridge) , Christopher W. Ashling (University of Cambridge) , Philip A. Chater (Diamond Light Source) , David Keen (ISIS Facility) , Thomas D. Bennett (University of Cambridge) , Yuanzheng Yue (Aalborg University; Wuhan University of Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Chemistry Chemical Physics , VOL 423

State: Published (Approved)
Published: June 2018
Diamond Proposal Number(s): 171151

Abstract: In this work, we explore the thermodynamic evolution in a melt-quenched metal–organic framework glass, formed from ZIF-62 upon heating to the melting point (Tm), and subsequent enthalpy relaxation. The temperature dependence of the difference in Gibbs free energy between the liquid and crystal states of ZIF-62 in the temperature range from the glass transition temperature (Tg) to Tm is found to be weaker than those of other types of glasses, e.g., metallic glasses. Additionally, we find that the stretched exponent of the enthalpy relaxation function in the glass varies significantly (β = 0.44–0.76) upon changing the extent of sub-Tg annealing, compared to metallic and oxide glasses with similar Tgs, suggesting a high degree of structural heterogeneity. Pair distribution function results suggest no significant structural changes during the sub-Tg relaxation in ZIF-62 glass.

Subject Areas: Materials, Chemistry

Instruments: I15-1-X-ray Pair Distribution Function (XPDF)