Sugar, salt, and a little alcohol led to the discovery of a new class of nanostructures that could aid in gas storage and food and medical technologies.
The porous crystals are the first known all-natural metal-organic frameworks (MOFs) that are simple to make, said researchers at Northwestern University. Most other MOFs consist of petroleum-based ingredients, but the Northwestern MOFs you can pop into your mouth and eat, and the researchers have.
“With our accidental discovery, chemistry in the kitchen has taken on a whole new meaning,” said Sir Fraser Stoddart, Board of Trustees Professor of Chemistry in the Weinberg College of Arts and Sciences at Northwestern. The applications of this discovery cover cleaner air to healthier living, and it all comes from a product you can wash down the sink.
Metal-organic frameworks consist of well-ordered, lattice-like crystals. The nodes of the lattices are metals (such as copper, zinc, nickel or cobalt), and organic molecules connect the nodes. Within their very roomy pores, MOFs can effectively store gases such as hydrogen or carbon dioxide, making the nanostructures of special interest to engineers as well as scientists.
With these ingredients in hand, the researchers actually had set out to make new molecular architectures based on gamma-cyclodextrin. Their work produced crystals. Upon examining the crystals’ structures using X-rays, the researchers discovered they had created metal-organic frameworks.
It turns out gamma-cyclodextrin solves the problem: it comprises eight asymmetrical glucose residues arranged in a ring, which is itself symmetrical. The gamma-cyclodextrin and potassium salt dissolve in water and then crystallize by vapor diffusion with alcohol.
The resulting arrangement crystals consisting of cubes made from six gamma-cyclodextrin molecules linked in three-dimensions by potassium ions was previously unknown. The research team believes the strategy of marrying symmetry with asymmetry will carry over to other materials.
“It is both uplifting and humbling to come to terms with the fact that a piece of serendipity could have far-reaching consequences for energy storage and environmental remediation on the one hand and food quality control and health care on the other,” Stoddart said.