Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

RUB chemists develop a new preparation process for MOFs

04.05.2009
Large void storage volume within molecular-organic frameworks
New functional materials thanks to "intelligent" substrates

Many molecular materials, be they hydrogen for fuel cells or drugs, can be stored in metal-organic frameworks (MOFs).

This would even be possible for metal nano particles for catalysis, were there not one little hindrance: if the void spaces in the MOF are too large, a second embedded framework system automatically develops during the synthesis process. This "uncontrolled proliferation" leads to a significant reduction in the size of the voids.

A team of chemical scientists at the Ruhr-University in Bochum, working under the auspices of Prof. Christof Wöll and Prof. Roland A. Fischer have now managed to solve this major problem by developing an alternative preparation process. They do not allow the entire metal-organic framework to develop in one single step, but grow it layer-by-layer on an "intelligent" organic surface. This enables the formation of voids that are large enough for metal particles. The scientists have documented their results in the current edition of NATURE Materials.

Void spaces are too small for metals

The highly porous MOFs usually reveal two different types of structural elements. Transverse bars comprised of organic molecules are connected by inorganic coupling units containing metal ions. Mixing these reactants and heating leads to self-organized formation of MOFs. These metal-organic frameworks are of global interest because they can be loaded with the most diverse of materials. Prof. Wöll explained that the spectrum ranges from the storage of liquid hydrogen in the tank of a car all the way to a storage site for drugs. These "porous" materials are also of interest for heterogeneous catalysis. For this purpose, metal particles are embedded in the pores - this does, however, necessitate relatively large void spaces. Prof. Fischer pointed out that this has been a fundamental problem in the synthesis of MOFs to date. If the pores are too large, numerous instances of the MOF lattice develop simultaneously, forming an interlaced network of numerous structures. This in turn leads to reduction in the size of the individual voids within the frameworks.

Layer-by-layer production of larger frameworks

The scientists at the Departments of Physical Chemistry (Wöll) and Inorganic Chemistry (Fischer) at the Ruhr-University in Bonn (RUB) can now bypass this interpenetration problem. They developed a new synthesis procedure, described as liquid phase epitaxy, which differs from the usual synthesis (i.e. mixing all the reactants in solution and subsequent heating thereof). Intelligent surfaces coated with substrates are alternately dipped into pots each of which contains only one type of MOF structural element. The organic surfaces ensure that only one structural alternative of the MOF develops, thus avoiding interpenetration and yielding the desired large void spaces. Prof. Wöll is pleased to announce that it is thus now possible to produce materials with significantly larger pores than had been the case to date. Currently the scientists are trying to store metal clusters in the spacious voids. These in turn could be used for heterogeneous catalysis and sensorics.

Intelligent surfaces

The scientists produce the intelligent surfaces that ensure that exactly the desired MOFs develop by self-assembly: simply dipping metal substrates into solutions of so-called organothiols (sulphurous organic molecules) yields a high-quality organic coating. The sulphur atoms bind tightly to the metal substrate, thus acting as anchors for the organic molecules, yielding self-assembled monolayers (SAMs). The growth of the frameworks on the surface of the SAMs can then be controlled by the particular choice of the organothiol. It is even possible to "dictate" their orientation by using "tailor-made" SAMs

Title

Osama Shekhah, Hui Wang, Markos Paradinas, Carmen Ocal, Björn Schüpbach, Andreas Terfort, Denise Zacher, Roland A. Fischer, and Christof Wöll: Controlling Interpenetration in Metal-Organic Frameworks by Liquid Phase Epitaxy. In: Nature Materials, 3.5.2009, DOI: 10.1038/NMAT2445

Further Information

Prof. Christof Wöll, Department of Physical Chemistry I at the Ruhr-University Bochum, D-44780 Bochum, Germany, Tel: +49 (0) 234/32-25529, Fax: +49 (0) 234/32-14182, E-Mail: woell@pc.ruhr-uni-bochum.de, Faculty-Homepage: http://www.pc.rub.de

Dr. Josef König | idw
Further information:
http://www.pc.rub.de

More articles from Life Sciences:

nachricht World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Microscopic trampoline may help create networks of quantum computers

17.07.2018 | Information Technology

In borophene, boundaries are no barrier

17.07.2018 | Materials Sciences

The role of Sodium for the Enhancement of Solar Cells

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>