Organic compounds show promise as cheaper alternatives to metal photocatalysts

Organic compounds that can be sustainably and affordably mass-produced hold promise as a replacement for expensive metal photocatalysts, according to a new report published on July 17.

Researchers at the University of St Andrews have shown that a family of four organic compounds originally developed as emitters for organic light-emitting diodes performed as well as, and in some cases better than, archetypal photocatalysts.

The findings are reported in the journal Chem Catalysis.

Many traditional photocatalysts contain rare, expensive and toxic metals

Professor Eli Zysman-Colman, an expert in optoelectronic materials from the School of Chemistry at St Andrews, said: “Photocatalysis, which involves the use of light and a dye to initiate the process of making compounds, has advanced at an incredible rate over the past 15 years. flight.

“The central problem is that many archetypal photocatalysts contain metals such as ruthenium and iridium. These are rare, expensive and toxic. This makes them unattractive for use in later stages in the pharmaceutical and agrochemical industries.”

“There is a real need for viable alternatives to these metal-based photocatalysts, especially ones that show strong reactivity, which is one of my group’s research goals.”

Promising alternatives

Zysman-Colman and Ph.D. student Lea Hämmerling tested four multi-resonance thermally activated delayed fluorescence (MR-TADF) compounds containing boron and nitrogen as photocatalysts in a series of comparative reactions.

Zysman-Colman said: “We found that the intrinsic properties of these compounds – their strong absorption in the visible part of the spectrum, the relative insensitivity of their excited states to solvent polarity, and their electron-rich nature – would make them very accessible. as strongly photoreducing photocatalysts.

“We found that when used in such reactions as pinacol coupling, dehalogenation, and E/Z isomerization, the MR-TADF compounds performed as well or slightly better than several commonly used photocatalysts.

“This is important: we have shown that this family of sustainable organic materials works competently in a wide range of transformation types.

“This should make them attractive photocatalysts for a wide range of applications, including industries such as pharmaceuticals and agriculture, which would prefer access to alternative photocatalysts to avoid trace metal contamination in the final product.”

Zysman-Colman co-coordinates the PhotoReact Innovative Training Network involving academia and industry to address the challenges of photocatalysis.

He adds: “Photocatalysis is a powerful synthetic tool that has changed the way we make and access a wide range of chemicals, and offers the promise of a much more sustainable future for the production of these compounds.”