Sugary Networks

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Science  06 Jan 2012:
Vol. 335, Issue 6064, pp. 15
DOI: 10.1126/science.335.6064.15-a
CREDIT: FORGAN ET AL., J. AM. CHEM. SOC. 10.1021/JA208224F (2011)

The burgeoning development of metal organic framework (MOF) solids has primarily relied on the versatile coordination geometries of transition metal ions, which function as lattice nodes bridged in several dimensions by multifunctional ligands. Forgan et al. present an in-depth study of a very different class of solids that still fall under the MOF rubric. Alkali cations such as potassium and rubidium replace the traditional transition metals, and the organic components are γ-cyclodextrins—rings of eight covalently tethered sugar molecules better known for one-dimensional encapsulation than for network formation. Body-centered cubic frameworks were crystallographically characterized and proved robust to removal of solvent after their self-assembly in solution. The use of smaller sodium or larger cesium ions led to several different polymorphs, as did divalent strontium, though transition metals proved poor at directing assembly. Among the potassium-linked variants prepared by the authors was a MOF composed entirely of food-grade materials.

J. Am. Chem. Soc. 10.1021/ja208224f (2011).

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