Melt non-fusible organo-metallic compounds

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Glasses are vital materials in everyday life. One of the main reasons for this is that it is possible to manufacture glasses globally in several shapes and sizes at low cost, using the corresponding melting techniques.

Vahid Nozari uses a microscope to examine the new synthetic glass made from MOF material. Image credit: Jens Meyer (University of Jena).

The treatment of glass in a viscous state offers a versatility that can hardly be achieved with other materials. However, this does not imply that it is possible to melt the material from which glass is produced in terms of chemical composition.

Organometallic compounds called MOF have gained more attention in recent years. Their unique characteristics make them a potential candidate for future applications such as energy and environmental technologies, sensor components and in the biological and life sciences.

For example, MOFs can be used as raw materials for filter membranes, which are used to separate gases in technical combustion processes or for water treatment. The basis for this multiple application is the specific property of MOFs, i.e. their high and largely controllable porosity.

MOF substances include particles that are combined by organic molecules to form a network of pores. As MODs are mainly in powder form, a significant difficulty is the mass production of components. Here, glasses play an important role.

Trade-off between properties and processability

The porosity of the materials prevents them from being fusible and convertible into components of the required shape, with a few exceptions. Chemists from Friedrich Schiller University in Jena, Germany, and the University of Cambridge, UK, have now discovered a solution to this problem. The study was published in the journal Nature Communication.

To use MOFs to produce components for industrial production, they can be made into so-called hybrid glasses, for example. To do this, they have to be melted, which is not a straightforward process in this particular case. So far, only a few materials of this class have been proven to be fuses.

In most of the known MOF materials, the high porosity is one of the reasons why, upon heating, they thermally decompose before reaching their melting point, i.e. they burn..

Vahid Nozari, PhD student, Laboratory of Glass Science, University of Jena

This is an interesting property which also protects them from treatment by the glass route.

Identification of combinations of ionic liquids, MOF matrices and melting conditions

The method of melting a non-fusible material to shape and process it in a liquid state was discovered by a team of researchers led by Professor Jena Lothar Wondraczek.

We filled the pores with an ionic liquid that stabilizes the inner surface so that the substance can finally melt before it even breaks down..

Lothar Wondraczek, Principal Investigator, University of Jena

Researchers have successfully demonstrated the process by which non-fusible substances of the zeolite imidazolate (ZIF) framework MOF family can be melted to form a liquid state and then into a glass.

In this way, the desired component can be obtained, for example, in the form of a membrane or a disc. Residues of the ionic liquid used can then be washed after shaping.

Lothar Wondraczek, Principal Investigator, University of Jena

The key to future applications lies in the interactions that occur between the ionic liquid and the MOF material. These quantify the reversibility of the process, that is to say the possibility of leaching the auxiliary liquid from the post-melting process.

The pore surface is not sufficiently stabilized or an irreversible chemical bond occurs between the MOF and parts of the ionic liquid due to non-adaptation of the reactions. Therefore, it is necessary to identify the optimal combinations of liquids, matrix materials and melting conditions corresponding to the desired application, paving the way for large volume objects.

Journal reference:

Nozari, V., et al. (2021) The ionic liquid facilitated the fusion of the ZIF-8 metallo-organic framework. Nature Communication. doi.org/10.1038/s41467-021-25970-0.

Source: https://www.uni-jena.de/en


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