hot water catalyst

The research team of chemist Miriam Unterlass succeeded in producing organic and inorganic substances in a single process using an environmentally friendly method.

The production of chemical substances normally requires environmentally harmful solvents. After the research group of Miriam Unterlass, professor of solid state chemistry at the University of Konstanz, produced organic substances without harmful substances for the first time by heating them in hot water, researchers can now record another success: thanks to hydrothermal synthesis, they succeeded in forming and combining organic and inorganic substances jointly in the same reactor. Specifically: an inorganic solid that contains organic dye molecules. When exposed to light, which is by far the most environmentally friendly energy resource, the hybrid material functions as a catalyst, i.e. a photocatalyst. The photocatalyst being a solid, it can be used several times.

The study was recently published online by the Journal of Materials Chemistry A. In the next print edition of the journal (issue 24, year 2022), the study will be featured on the cover page.

Hydrothermal synthesis, that is, the production of materials under pressure in hot water, is modeled on nature. In underground hot water reservoirs, for example, rock crystals form when atoms dissolved in hot water react with each other, forming first molecules and then crystals. In the same way, inorganic molecules can be produced in synthetic chemistry – and as described in a study on the environmentally friendly process in the synthesis of organic substances from 2021 by Miriam Unterlass – also organic molecules without solvents toxic.

Environmentally friendly synergy of the two processes An environmentally friendly synergy of the two methods stems from the current findings, in which first author Dr Hipassia Moura, postdoctoral researcher in Miriam Unterlass’s team, plays a major role. Miriam Unterlass: “In our work, we show that it is possible to form inorganic and organic substances at the same time in ‘hot water’, and that something useful comes out of it.

The fact that the hybrid material can be produced completely without toxic solvents is all the more remarkable as the chemist’s research team is working with dye molecules that normally require highly toxic chemicals for their synthesis. The core of the new substance, which was created in hot water, is formed by dye molecules that exist in the form of a solution, while the material around them has the properties of a solid. The result is a solid that behaves like a solution in terms of optical properties.

Reusable catalyst

Dyes in solution have very specific properties. The dye molecules used by Miriam Unterlass’ research team are able to absorb light and therefore catalyze reactions. This process is similar to photosynthesis in plants, where they are also pigments that absorb the light needed for photosynthesis. Unlike a solution that has to be discarded after use, the hybrid material has the added benefit of being able to be used again and again as a catalyst, as it is like a solid on the outside.

The research team’s specific application target are small organic molecules that play a role in pharmaceuticals. In principle, however, the method is relevant for various chemical reactions and thus the production of countless synthetic products. And while water still needs to be heated for the synthesis of the hybrid material, only light energy is needed for the catalytic effect. “Light is the best resource we have. Light cannot be exhausted,” says Miriam Unterlass.


  • Study on the environmentally friendly hydrothermal synthesis of a substance with both organic and inorganic properties in a single process
  • Synthesis without toxic solvents
  • The resulting hybrid material can be used as a catalyst that derives its energy from light
  • The study was carried out as part of the START Y1037-N38 project and was funded by the Austrian Science Fund (FWF).

Source of the story:

Materials provided by University of Konstanz. Note: Content may be edited for style and length.

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