Dr. Albert Ruggi from the Department of Chemistry has recently published a new article in the journal ChemSusChem, entitled "Catalytic CO2 Reduction with Heptacoordinated Polypyridine Complexes: Switching the Selectivity via Metal Replacement". 

For more information and to read the article: https://chemistry europe.onlinelibrary.wiley.com/doi/full/10.1002/cssc.202300737

Abstract

The discovery of molecular catalysts for the CO₂ reduction reaction (CO₂RR) in the presence of water, which are both effective and selective towards the generation of carbon-based products, is a critical task. Herein we report the catalytic activity towards the CO₂RR in acetonitrile/water mixtures by a cobalt complex and its iron analog both featuring the same redox-active ligand and an unusual seven-coordination environment. Bulk electrolysis experiments show that the cobalt complex mainly yields formate (52 % selectivity at an applied potential of −2.0?V vs Fc⁺/Fc and 1 % H₂O) or H₂ (up to 86 % selectivity at higher applied bias and water content), while the iron complex always delivers CO as the major product (selectivity >74 %). The different catalytic behavior is further confirmed under photochemical conditions with the [Ru(bpy)₃]²⁺ sensitizer (bpy=2,2’-bipyridine) and N,N-diisopropylethylamine as electron donor, where the cobalt complex leads to preferential H₂ formation (up to 89 % selectivity), while the iron analog quantitatively generates CO (up to 88 % selectivity). This is ascribed to a preference towards a metal-hydride vs. a metal-carboxyl pathway for the cobalt and the iron complex, respectively, and highlights how metal replacement may effectively impact on the reactivity of transition metal complexes towards solar fuel formation.