Coordinatively fluxional diazo-based organo-electrocatalyst for conversion of CO2 to C2 and C3 products

Abstract

The conversion of carbon dioxide (CO2) into valuable chemicals, specifically C2 and C3, through metal-free electrocatalysis remains a formidable challenge. Breaking away from traditional transition metal complexes, the focus is on designing and selecting efficient organic catalysts. In this pursuit, a diazo-based organic bulky ligand emerges as a promising candidate, offering a solution that is both sustainable and renewable. The key feature of this ligand is its low-lying π* (LUMO), enabling it to readily accept an electron in an electrochemical environment when a potential is applied. The synthesized Diazo-based ligands have been meticulously characterized using various techniques, including 1H NMR, 13C NMR, UV-Vis, and IR spectroscopy. This diazo-based ligand serves as an electrocatalyst, undergoing reduction to a triplet diradical that acts as a nucleophile. In an aqueous medium, it forms an adduct with CO2, leading to the generation of a formyl radical. This radical further couples to produce acetic acid and acetone with efficiencies of 19.6% and 24.2%, respectively, at pH 5.5. To provide a deeper understanding, we present a proposed mechanism pathway supported by in-situ UV-Vis spectroscopy and a comprehensive Density Functional Theory (DFT) study. These findings mark a significant step forward in the field of metal-free electrocatalysis, offering a sustainable approach to the conversion of CO2 into valuable chemicals, contributing to the development of renewable and environmentally friendly systems.