01 Dez. Light as a tool for sustainable chemistry
For centuries, chemistry worked as follows: chemists heated their reaction vessels to activate the substances inside them. “With light, I can overcome the activation barrier much faster and with much greater amounts of energy,” says Dr. Jola Pospech from the Leibniz Institute for Catalysis (Likat) in Rostock. Pospech and her team are developing new approaches to classic reaction pathways in photocatalysis. Photocatalysis is a process in which a catalyst accelerates chemical reactions under the influence of light. The research group often uses black light, i.e., UV-A light that is just visible, as a light source in the laboratory. “In our case, this light has the right wavelength to trigger chemical reactions,” explains Pospech. “We direct the LED panel onto the reaction vessel, where the photons strike the outer electron pairs of the substances involved, in our case the catalyst, which then enters an excited state.” This means that it is now able to release or absorb an electron and thus activate chemical starting materials. Ultimately, new chemical compounds are formed when the substances involved exchange or share electrons.
Light instead of heat
Dr. Jola Pospech heads the Catalytic Functionalization department at Likat. Image: Likat
Modern LED technology allows the wavelength of the light source to be precisely matched to the absorption spectrum of the catalyst. The chemist cites hydrofunctionalization as an example: the substances involved are converted down to the last atom, without any by-products. This produces products such as bioactive amines, which occur naturally in neurotransmitters and are important for drug development.
Many of these reactions have so far been carried out with catalysts made of scarce and expensive metals, involving many intermediate steps, co-catalysts, and so-called sacrificial reagents. Pospech: “These serve only to donate an additional electron so that another electron can change partners energetically at the appropriate point.”
Inexpensive, precise, and suitable for industrial use
Her research group developed alternative organic photoredox catalysts consisting of nitrogen, hydrogen, oxygen, and carbon. “The compounds we use are inexpensive to manufacture, can be activated precisely and quickly using black light, and are mechanistically multifunctional.” This eliminates the need for co-catalysts and sacrificial reagents.
According to Pospech, there is considerable motivation in practice to apply such findings from basic research to industrial applications. At least in the long term. “Every major chemical company now has research departments for photocatalysis and electrochemistry.” Likat is, so to speak, at the cutting edge.
Source and image: www.catalysis.de