Graphitic carbon nitride is able to replace iridium as a photocatalyst in cross coupling reactions, greatly reducing cost and carbon footprint, according to a study in Angewandte Chemie.

Organic chemists are continuously looking to improve C-C-coupling reactions, as the carbon-carbon bond is one of the most fundamental bond-types in chemistry. Specifically, coupling reactions between a carbon atom with a double bond [C(sp²)] and single bonds [C(sp³)] have become more and more important due to the bond type’s abundant appearance in pharmaceuticals, for example.

To make these C(sp²)–C(sp³) bonds photocatalytically, you can use a combination of iridium catalyst, nickel catalyst and blue light, which works great. ‘But iridium is five times more expensive than platinum or palladium, and both where and how it’s extracted and refined poses environmental and ethical questions’, says Benjamin Martin, Continuous Manufacturing Network Leader at Novartis. To deal with these concerns, Martin and colleagues from Novartis teamed up with the research group of Timothy Noël at the University of Amsterdam to explore a relatively under-explored photocatalyst that could replace iridium: graphitic carbon nitride (gCN).