The chemical industry produces not just valuable vitamins, pharmaceuticals, flavours and pesticides, but often a large amount of waste, too. This is particularly true of pharmaceutical and fine-chemical production, where the volume of desired product may be just a fraction of the volume of waste and unsaleable by-products of synthesis. Catalysts are substances that speed up a chemical reaction. In the case of widely used dissolved catalysts, it often takes a huge amount of effort to separate them from the solvent and from the reaction products for reuse. Catalysts in solid form avoid this problem altogether.

In collaboration with Javier Pérez-Ramírez, Professor of Catalysis Engineering at ETH Zurich, Dr Sean Collins and Prof. Paul Midgley from Department of Materials Science and Metallurgy, University of Cambridge and a network of European colleagues have developed just such a solid catalyst for a major chemical reaction. The new catalyst is a molecular structure composed of carbon and nitrogen atoms (‘graphitic carbon nitride’) that features cavities of atomic dimensions into which  palladium atoms are placed. By making tiny particles of this palladium-carbon-nitrogen material, the team was able to show that the material catalyses what is known as the Suzuki reaction very efficiently.

Thus far, the process in commercial scale has widely used soluble palladium catalysts. Earlier attempts to attach the soluble catalyst to a solid body always resulted in relatively unstable and inefficient catalysts. The new palladium catalyst is much more stable. For that reason, and because it does not dissolve in the reaction liquid, it can be used over a much longer time period. What's more, the catalyst is much more cost-effective and around twenty times more efficient than the catalysts used today. This approach promises to enable the use other metals for a great range of important reactions with improved durability and efficiency.

Figure caption: Illustration of a single palladium atom in a carbon nitride cavity. Some movement is possible within the cavity, enabling adaptation to changes during the chemical reaction, but it remains trapped inside ensuring overall stability for continued use of the catalyst.