Single Iridium Pincer Complex for Roundtrip Electrochemical Conversion between Carbon Dioxide and Formate

Abstract

Abstract An iridium (III) complex based on a PONOP pincer ligand (PONOP=2,6‐bis(di‐tert‐butylphosphinito)pyridine) is a versatile catalyst for both electro‐reduction of CO 2 to formate and formate electro‐oxidation to CO 2 . The electro‐reduction of CO 2 in acetonitrile is very efficient and selective, and the Faradaic efficiency for formate was 97 % and the turnover frequency (TOF) was as high as 67 s −1 . In addition, the complex is an effective electrocatalyst for formate electro‐oxidation with apparent TOF of 4.8 s −1 (0.06 M formate), and CO 2 was the sole product. The catalyst was stable for 35 h of electrolysis. It can serve as a single catalyst for the roundtrip conversion between CO 2 and formate with potential for electrochemical energy storage. Electrochemical and NMR spectroscopic studies suggested that the hydride species is critical for the bifunctional reactivity.