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Massive Anisotropic Thermal Expansion and Thermo-Responsive Breathing in Metal–Organic Frameworks Modulated by Linker Functionalization

Authors

  • Sebastian Henke,

    Corresponding author
    1. Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK
    2. Lehrstuhl für Anorganische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
    • Sebastian Henke, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK

      Roland A. Fischer, Lehrstuhl für Anorganische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany.

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  • Andreas Schneemann,

    1. Lehrstuhl für Anorganische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
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  • Roland A. Fischer

    Corresponding author
    1. Lehrstuhl für Anorganische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany
    • Sebastian Henke, Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ, UK

      Roland A. Fischer, Lehrstuhl für Anorganische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44780 Bochum, Germany.

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Abstract

Functionalized metal–organic frameworks (fu-MOFs) of general formula [Zn2(fu-L)2dabco]n show unprecedentedly large uniaxial positive and negative thermal expansion (fu-L = alkoxy functionalized 1,4-benzenedicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane). The magnitude of the volumetric thermal expansion is more comparable to property of liquid water rather than any crystalline solid-state material. The alkoxy side chains of fu-L are connected to the framework skeleton but nevertheless exhibit large conformational flexibility. Thermally induced motion of these side chains induces extremely large anisotropic framework expansion and eventually triggers reversible solid state phase transitions to drastically expanded structures. The thermo-responsive properties of these hybrid solid–liquid materials are precisely controlled by the choice and combination of fu-Ls and depend on functional moieties and chain lengths. In principle, this combinatorial approach allows for a targeted design of extreme thermo-mechanical properties of MOFs addressing the regime between crystalline solid matter and the liquid state.

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