Issue Date: August 30, 2010
Making Edible Nanostructures
Common foodstuffs aren’t typical synthesis starting materials. But they’re exactly what a team of researchers used to make novel compounds that are porous, crystalline, and edible.
By starting with food-grade γ-cyclodextrin (CD), salt substitute (potassium chloride), and grain spirits (ethanol), researchers at Northwestern University and UCLA synthesized new types of metal-organic framework (MOF) compounds. The advance—which could have pharmaceutical and food science applications—was reported on Aug. 25, at the American Chemical Society national meeting in Boston (Angew. Chem. Int. Ed., DOI: 10.1002/anie.201002343).
MOF compounds, which consist of metal ions or clusters connected by organic linkers, have broad commercial appeal for use in gas storage and purification, catalysis, and chemical sensing.
But as the study’s first author, Ronald A. Smaldone, a postdoc working with Northwestern chemistry professor J. Fraser Stoddart, explained, the vast majority of MOFs described to date are composed of organic units derived from nonrenewable petrochemical feedstocks and transition metals. Making the compounds from nontoxic, biorenewable starting materials would be environmentally advantageous and could offer cost savings. But that task has remained challenging due to the inherent asymmetry of many natural building units and the difficulty in using them to synthesize crystalline porous products.
To sidestep that problem, the Northwestern team, UCLA’s Omar M. Yaghi, and coworkers linked γ-CD—a symmetrical oligosaccharide composed of asymmetrical units and produced commercially from starch—with potassium ions and separately with other alkali ions to form a new family of CD-MOF compounds.
“Edible MOFs are a stunning example of the power of self-assembly from simple and readily available components,” said Leonard R. MacGillivray, a University of Iowa chemistry professor. This work will likely challenge other researchers to seek the design and construction of frameworks from renewable and benign starting materials, he said. MacGillivray added that the study suggests that merging function and issues of sustainability is a real possibility in this rapidly developing area.
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