A few atoms of palladium, spread across a solid made from carbon nitride, helped researchers build useful carbon-carbon bonds—and then be cleaned and used again. The new catalyst, developed by teams at EPFL in Lausanne and ETH Zurich, offers a way to make some complex chemicals with fewer preparatory steps and less loss of a precious metal.
Many chemical reactions rely on catalysts, materials that help reactions happen without being used up in the process. But common methods for joining molecules often require chemists to add special reactive groups to their starting materials first. Those extra steps take time and can create waste. A more direct approach, called C-H functionalization, works with carbon-hydrogen bonds already found in molecules. It can help create compounds used in medicines and other fine chemicals, but has often depended on large amounts of palladium that are difficult to recover and recycle.
The research team was led by Jérôme Waser at EPFL and Javier Pérez-Ramírez at ETH Zurich, as part of NCCR Catalysis. They designed a catalyst in which individual palladium atoms sit apart from one another on a solid support. The atoms remain active, while the solid can be separated from a reaction mixture by filtration.
Finding a support that could hold on to the palladium was an early hurdle. On many materials, the metal escaped during the reaction. The team found that carbon nitride, an inexpensive organic material, kept the palladium in place. But the stable catalyst was initially too slow. A small amount of a phosphine compound brought its activity back without sacrificing stability, allowing the reaction to reach yields of up to 83 percent.
The catalyst also lost activity after its first use. To find out why, researchers used X-ray absorption spectroscopy at the Paul Scherrer Institute. They discovered that iodide was binding strongly to the palladium atoms and blocking the sites where reactions occur. The team then developed washing treatments that restored the catalyst's activity for as many as five cycles.
Across those uses, the catalyst achieved a cumulative turnover number above 200. In simple terms, each catalyst molecule helped make more than 200 product molecules. The researchers say the current best catalyst for this reaction reaches about 20 turnovers, making the new result roughly ten times higher.
The catalyst is not an unlimited-use solution: it cannot be reused indefinitely, and repeated cleaning changes its support. Still, the work shows that single-atom catalysts can perform demanding C-H functionalization while allowing palladium to be recovered and reused. The study, by Valentas Olikauskas and colleagues, was published in the Journal of the American Chemical Society in 2026. The team’s next challenge is to understand how to preserve the catalyst through more cycles and bring this more direct chemistry closer to practical production.