Moving Metal-Organic Frameworks in Different Directions: Liquids, Glasses, Composites and PT Phase Diagrams

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Moving Metal -Organic Frameworks in Different Directions: Liquids, Glasses, Composites and PT Phase Diagrams Bennett, Thomas D
Metal -organic frameworks (MOFs) are microporous materials with huge potential as host structures for chemical processes, including retention, catalytic reaction, or separation of guest molecules. Structural collapse at high -pressure, and unusual behaviours at elevated temperatures, such as melting and transitions to liquid states, have recently been observed in the family. 1, 2 Here, we discuss not only the mechanism of melting and the structure of the resultant glasses, but we also show that the effect of the application of simultaneous high -pressure and -temperature on a MOF can be understood in terms of silicate analogues, with crystalline, amorphous and liquid states occurring across the pressure - temperature phase diagram. The response s of ZIF -4, and ZIF -62, the MOF s on which we focus, to simultaneous pressure and temperature reveals a complex behaviour with distinct high - and low - density amorphous phases , crystalline polymorphs and liquid states occurring o ver different regions of the pressure -temperature space. 3, 4 Figure 1. Experimentally derived P -T phase diagram for ZIF -62 a, The stability fields for crystalline ZIF -62 (blue), amorphous (red) and liquid (yellow). The phase - field for liquid ZIF -62 is defined by melting points (black diamonds) observed optically at high -pressure and using DSC at ambient pressure. Crosses indicate high -pressure/high -temperature conditions from which the samples were quenched for morphological analysis. b, c, and d, Scanning -electron microscopic images of the three main phases of ZIF -62. 1. T. D. Bennett and S. Horike, Nat Rev Mater , 2018, 3, 431 -440. 2. R. Gaillac, P. Pullumbi, K. A. Beyer, K. W. Chapman, D. A. Keen, T. D. Bennett and F. X. Coudert, Nat Mater , 2017, 16, 1149 -1154. 3. R. N. Widmer, G. I. Lampronti, S. Anzellini, R. Gaillac, S. Farsang, C. Zhou, A. M. Belenguer, C. W. Wilson, H. Palmer, A. K. Kleppe, M. T. Wharmby, X. Yu, S. M. Cohen, S. G. Telfer, S. A. T. Redfern, F. X. Coudert, S. G. MacLeod and T. D. Bennett, Nat Mater , 2019, 18, 370 -+. 4. R. N. Widmer, G. I. Lampronti, S. Chibani, C. W. Wilson, S. Anzellini, S. Farsang, A. K. Kleppe, N. P. M. Casati, S. G. MacLeod, S. A. T. Redfern, F. X. Coudert and T. D. Bennett, J Am Chem Soc , 2019, 141 , 9330 -9337.
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  • Speaker

    Dr Tom Bennett

  • Venue

    Theatre D, Purdie

  • Date

    November 19, 2019

  • Time

    From: 9h00 To: 10h00

  • Sponsor

    University of St Andrews
    The oldest university in Scotland, with international renown for both research and education of undergraduates and postgraduates.

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