Tiny MOFs that Glow

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Science  14 Jul 2006:
Vol. 313, Issue 5784, pp. 148
DOI: 10.1126/science.313.5784.148b

The structural tunability of metal organic framework (MOF) solids, in which bridging organic ligands form a scaffold by coordinating to metal ions, has proven useful in bulk applications such as gas sorption. Pushing toward the opposite end of the size spectrum, Rieter et al. present a controlled approach to the synthesis of discrete nanometer-scale MOF assemblies. They combined trivalent gadolinium ions with a benzenedicarboxylate (BDC) salt in a microemulsion, created through surfactant addition to an isooctane/hexanol/water mixture. By modifying the water-to-surfactant ratio, the authors could tune the size of the resultant Gd(BDC)1.5(H2O)2 rods from ∼100 nm to ∼1 μm in length, and ∼40 to ∼100 nm in diameter. The high gadolinium density in the rods is advantageous for contrast enhancement in magnetic resonance imaging; the rods evidenced remarkably high relaxivities (>107/s/mmol) during test runs using aqueous xanthan gum suspensions. Doping with alternative metals increased the versatility of potential imaging applications: addition of 5 mole % of either europium or terbium during the synthesis respectively induced red or green luminescence on ultraviolet irradiation of the rods in solution. — JSY

J. Am. Chem. Soc. 128, 10.1021/ja0627444 (2006).

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