The first programmable photocatalyst

With smart materials toward more sustainable chemistry

Researchers at the Max Planck Institute of Colloids and Interfaces have developed a sustainable and smart photocatalyst. The special feature: as a so-called smart material, it can distinguish between the colors of light (blue, red and green) and, in response, enables a specific chemical reaction.

"Our smart photocatalyst functions as a traffic guide who opens one specific pathway in response to light of specific color," says Yevheniia Markushyna, researcher at the Max Planck Institut for Colloids and Interfaces. Photocatalysts are special materials that use the energy from sunlight or LED light to enable a desired reaction. Often, this results in not just one product, but a variety. Chemists call this poor selectivity because separation of the desired product from the mixture consumes time and resources.

The colour of light controls the reaction

Quite different with the new method, which enables the research team for instance to synthesize sulfonamides in a targeted manner. Sulfonamides are organosulfur compounds that are used, among other things, as antibiotics to treat bacterial infections. The researchers have created a photocatalytically active carbon nitride material that produces with high selectivity sulfonamides. With the help of the sustainable smart photocatalyst, one product is created selectively from three possible from the same reagent by adjusting the color of the incident light. "The special feature is that we can control the selectivity of the chemical reaction by turning on the light bulb of the right color," says Yevheniia Markushyna. "Today, we have sustainable smart photocatalysts and the knowledge to produce value-added organic compounds using solar light in the most efficient way possible," says Aleksandr Savateev, group leader at the Max Planck Institute for Colloids and Interfaces. He adds, "Potentially, our method could also make the production of sulfonamide antibiotics more sustainable."

Complex biological objects, such as the human eye or state-of-the-art cameras in electronic devices can perceive light colors. It is a great challenge to develop smart molecules consisting of only tens of atoms. Such molecule must not only recognize the light colors (blue, red and green), but also perform a certain “programmed” action that depends on the specific light color.