A spoonful of sugar, a pinch of salt, and a splash of alcohol – those are the ingredients used by scientists to generate a new class of robust nanoporous metal–organic frameworks.
However, the sugar is not ordinary table sugar, but ã-cyclodextrin, produced from biorenewable cornstarch. As Fraser Stoddart and a team of scientists from Northwestern University in Evanston (IL, USA), the University of California in Los Angeles (USA), and the University of St. Andrews (UK) report in the journal Angewandte Chemie, this simple recipe could be the basis for a new class of biocompatible porous crystals made of renewable natural products.
Metal–organic frameworks (MOF) are well-ordered, lattice-like crystals. The nodes of the lattices are complexes of transition metals (such as copper, zinc, nickel, or cobalt); organic molecules make up the connections between the nodes. Within their pores, the MOFs can store gases such as hydrogen or carbon dioxide. Furthermore, they can be used for separation of materials, for catalysis, or for the targeted transport of drugs in the body. Most previously prepared MOFs are made of building blocks that stem from petrochemicals. Stoddart and his team set themselves a challenge to synthesize MOFs from natural products. “The problem is that natural building blocks are generally not symmetrical,” according to Stoddart, “this lack of symmetry seems to prevent them from crystallizing as highly ordered, porous frameworks.”
ã-Cyclodextrin provided the solution to this problem: it comprises eight asymmetrical glucose residues arranged in ring, which is itself symmetrical. In many countries (for example the USA and Japan), cyclodextrins are approved for use as food additives. The second ingredient in the frameworks is an alkali metal salt. Suitable candidates include ordinary table salt (sodium chloride), the common salt substitute potassium chloride, or potassium benzoate, an approved preservative. These ingredients are dissolved in water and then crystallized by vapor diffusion with an alcohol. It is even possible to use commercially available sources such as grain alcohol. “These ingredients are all substances that can be obtained cheaply, in high quality, and of food-grade purity,” says Stoddart.
The resulting crystals consist of cubes made from six ã-cyclodextrin molecules that are linked in three dimensions by potassium ions. These cubes are perfectly arranged to form a porous framework with easily accessible pores. “This arrangement is a previously unknown one,” says Stoddart. “The pore volume encompasses 54% of the solid body.” Particularly atypical of porous materials is the fact that when dissolved in water, the framework simply dissociates back to its components, which can then be crystallized again with alcohol. Says Stoddart: “In this way a degraded framework can easily be recycled or regenerated.”
Author: J. Fraser Stoddart, Northwestern University, Evanston (USA), http://stoddart.northwestern.edu/
Title: Metal-Organic Frameworks from Edible Natural Products
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201002343
The birth of a new protein
20.10.2017 | University of Arizona
Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research