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Issue 22, 2013
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Solvent-modified dynamic porosity in chiral 3D kagome frameworks

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Dynamically porous metal-organic frameworks (MOFs) with a chiral quartz-based structure have been synthesized from the multidentate ligand 2,2′-dihydroxybiphenyl-4,4′-dicarboxylate (H2diol). Compounds [Ni(II)(H2diol)(S)2xS (where S = DMF or DEF) show marked changes in 77 K N2 uptake between partially desolvated [Ni(II)(H2diol)(S)2] (only the pore solvent is removed) and fully desolvated [Ni(II)(H2diol)] forms. Furthermore, [Ni(II)(H2diol)(DMF)2] displays additional solvent-dependent porosity through the rotation of DMF molecules attached to the axial coordination sites of the Ni(II) centre. A unique feature of the four coordinate Ni(II) centre in [Ni(II)(H2diol)] is the dynamic response to its chemical environment. Exposure of [Ni(II)(H2diol)] to H2O and MeOH vapour leads to coordination of both axial sites of the Ni centres and to the generation of a solvated framework, whereas exposure to EtOH, DMF, acetone, and MeCN does not lead to any change in metal coordination or structure metrics. MeOH vapour adsorption was able to be tracked by time-dependent magnetometry as the solvated and desolvated structures have different magnetic moments. Solvated and desolvated forms of the MOF show remarkable differences in their thermal expansivities; [Ni(II)(H2diol)(DMF)2]·DMF displays marked positive thermal expansion (PTE) in the c-axis, yet near to zero thermal expansion, between 90 and 450 K, is observed for [Ni(II)(H2diol)]. These new MOF architectures demonstrate a dynamic structural and colourimetric response to selected adsorbates via a unique mechanism that involves a reversible change in the coordination environment of the metal centre. These coordination changes are mediated throughout the MOF by rotational mobility about the biaryl bond of the ligand.

Graphical abstract: Solvent-modified dynamic porosity in chiral 3D kagome frameworks

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Publication details

The article was received on 11 Jan 2013, accepted on 13 Feb 2013 and first published on 14 Feb 2013

Article type: Paper
DOI: 10.1039/C3DT00096F
Dalton Trans., 2013,42, 7871-7879

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    Solvent-modified dynamic porosity in chiral 3D kagome frameworks

    T. D. Keene, D. Rankine, J. D. Evans, P. D. Southon, C. J. Kepert, J. B. Aitken, C. J. Sumby and C. J. Doonan, Dalton Trans., 2013, 42, 7871
    DOI: 10.1039/C3DT00096F

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