A team of researchers, with participation from the Institute of Materials Science of Barcelona (ICMAB) (UAB Campus), the University of Girona, and the University of Valencia, has discovered that certain compounds made from abundant and inexpensive metals that incorporate boron and carbon atoms into the molecule can function as highly efficient catalysts when exposed to UVA light. These catalysts make it possible to oxidize alcohols and alkenes directly in water and using extremely small amounts of active material. The research opens the door to safer, more sustainable, and cheaper chemical processes, replacing the scarce and expensive metals commonly used in photocatalysis.

Abstract of the original article

Transition metal (TM) ions 4d⁶ or 5d⁶ configurations, typically used in photoredox catalysis, are often rare and expensive. In contrast, abundant first-row TM ions tend to favor metal-centered excited states, limiting their practical photocatalytic use. Here, we present two efficient 3d⁶ and 3d⁵ photoredox catalysts, [3,3′-Co(1,2-C₂B₉H₁₁)₂]⁻ and [3,3′-Fe(1,2-C₂B₉H₁₁)₂]⁻, with identical structures and charges (−1). Despite different electronic configurations, both catalysts deliver comparable performances in alcohol and alkene oxidation in water, even at low catalyst loadings (0.01 mol %). The catalysts are designed to operate in water without additional cosolvents, thanks to the surfactant properties of both θ-metallacarboranes. The impact of irradiating wavelength, explored through quantum chemistry, rationalizes their photocatalytic outcomes. Remarkably, 3d⁵ or 3d⁶ systems can match or outperform heavier TM analogs when supported by boron-based ligands, though selectivity differences highlight the role of metal electronic structure. UVA irradiation significantly boosts [o-COSAN]⁻ activity, offering new design insights for earth-abundant photoredox catalysts.