A group of researchers is making progress in developing new metallo-organic systems, Use special materials to build trash cans.
Discovered 25 years ago, metal organic frameworks (MOFs) quickly acquired the aura of “miracle materials” due to their unique properties: their large internal surface area and variable pore size enable rapid more efficient, such as in separation and gas storage. While previous representations were based on transition metals such as copper and zinc, a team from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) investigated other critical aspects of the periodic table: they studied similar compounds using actinides such as inorganic components. In this way, they contribute, among other things, to promoting the safe disposal of radioactive materials.
Rossendorf scientists thus laid the foundation (Use special materials to build trash cans) for a platform that can accommodate the actinide metal ion system as the main component, namely thorium and uranium as well as the transuranic elements neptunium and plutonium. “Many of these things below the timeline are man-made. They are the result of a neutron bomb or the result of a nuclear reactor.
Among them, humans have created dangerous substances because they are all radioactive and sometimes very toxic,” explains Dr. Moritz Schmidt of the Institute for Resource Ecology at the HZDR. “It also means that all our testing will be carried out using special security measures. Our workhorse is structural chemistry or, in other words, the creation of metal complexes with mostly organic molecules”, explains Dr. Juliane März, opening the position of the team.
In structural chemistry, organometallic frameworks are a growing field. Solids with a large composition of metal or oxygen clusters are connected modularly by a column of organic chemicals, creating a network of flexible holes reminiscent of the pores of a kitchen sponge. Initially, research focused on transition metals. “Good prospects for new applications made us interested in materials with complex electronic shells, first rare earths and finally actinides. But, now, there is almost nothing It is known about rare transuranic elements, such as neptunium and plutonium,” says März, explaining the timeline. High symmetry pairs from molecular building blocks – traditional applications
As an organic pillar, they are chemically modified with anthracene, an outstanding example of polycyclic aromatic hydrocarbons. “We know that crystal anthracene is the best organic scintillator: when rich radiation passes through this material, it excites its particles through a contraction process. The impulse energy is emitted as blue light. That’s why our frames are so shiny,” Schmidt reports. And they have another unique property: the width of their band gap, which is an example of the energy difference between the valence band and the conduction band. “In the case of very low-cost semiconductors, only the valence band contains charge carriers; in this case, it doesn’t matter. When power is applied, they move along the conduction band and thus cause the current to flow. Analysis shows that our innovation is called broadband semiconductor which plays a role in electronics and sensor technology in particular. Therefore, it can be used as a detector for ionizing radiation – and the actinides we combine at the same time provide a constant internal radiation reference,” enthuses Schmidt.
The first studies of MOFs by research groups around the world gathered agents that showed a significantly increased surface area and became an alternative for carbon and zeolites to work, for example in material separation or catalytic processes . Their advantage is that their modular structure makes it possible to implement different network topologies; Also, pore size can be very finely watched by choosing the right column for the intended application, as effective adsorbents for a specific specific chemical.
März and Schmidt continued by adding a new dimension to their work. They found an application in the area where HZDR’s Institute of Resource Ecology conducts research: radioactive waste. Researchers are considering the development of a suitable waste matrix that keeps the actinides in the scaffold and the fission products in its pores.
