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Synthesis and Characterization of Functionalized Metal-organic Frameworks
Published on: September 5, 2014
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A metal-organic framework with ultrahigh glass-forming ability
Ang Qiao1, Thomas D Bennett2, Haizheng Tao1
1State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, China.
Science Advances
|March 15, 2018
Summary
Researchers discovered zeolitic imidazolate framework-62 (ZIF-62) glasses exhibiting ultrahigh glass-forming ability (GFA). These novel materials surpass known glass formers in stability and resistance to crystallization.
Area of Science:
- Materials Science
- Chemistry
- Physics
Background:
- Glass-forming ability (GFA) is crucial for preventing crystallization in liquids.
- Metal-organic frameworks (MOFs) are emerging as a new class of glass formers with unexplored properties.
Purpose of the Study:
- To report the discovery of a new series of tetrahedral glass systems, zeolitic imidazolate framework-62 (ZIF-62).
- To characterize the exceptional glass-forming ability and properties of ZIF-62.
Main Methods:
- Synthesis and characterization of ZIF-62 glass systems.
- Measurement of key properties including viscosity, network density, fragility, Poisson's ratio, and glass transition temperature (Tg) relative to melting temperature (Tm).
Main Results:
- ZIF-62 glasses exhibit ultrahigh GFA, exceeding all known glass formers.
- Demonstrated high viscosity at Tm, large network density deficit, no crystallization on laboratory timescales, low fragility (m=23), high Poisson's ratio (ν=0.45), and the highest Tg/Tm ratio (0.84).
- Tg and Tm increase with benzimidazolate content while maintaining the ultrahigh Tg/Tm ratio.
Conclusions:
- The exceptional GFA of ZIF-62 is attributed to high steric hindrance, frustrated network dynamics, and the characteristic low enthalpy and entropy of MOFs.
- ZIF-62 represents a significant advancement in glass science, offering a new benchmark for glass-forming ability.
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