Total Electrosynthesis of N, N-Dimethylformamide From CO2 and NO3

Abstract

Electrochemical C-N coupling presents a promising strategy for converting abundant small molecules like CO₂ and NO₃ ^- to produce low-carbon-intensity chemicals in a potentially more sustainable route. A prominent challenge is the limited product scope, particularly for organonitrogen chemicals featuring a variety of functional groups, alongside the limited understanding of plausible reaction mechanisms leading up to these products. In light of this, the total electrosynthesis method is reported for producing N, N-dimethylformamide (DMF), a widespread solvent and commodity chemical, from NO₃ ^- and CO₂. This method enabled a notable production rate of 1.24 mmol h^-1 g_cat ^-1 for DMF employing a hybrid Ag/Cu catalyst. Additionally, an impressive Faradaic efficiency (FE) of 28.6% is attained for DMF through oxidative coupling of dimethylamine using Ag/Cu catalyst. Through a distinctive retrosynthetic experimental analysis, the DMF synthesis pathway is systematically deconstructed, tracing its origins from dimethylamine to methylamine, and ultimately to CO₂ and NO₃ ^-. The investigation revealed that the hydrogenation of coupled intermediates proves to be the limiting step, rather than the C-N coupling steps in the synthetic pathway. Finally, using a combination of in situ measurements and retrosynthetic analysis, the possible mechanism is elucidated underlying DMF synthesis and identified subsequent routes for system improvement.

Keywords: coupling; electrosynthesis; hydrogenation; retrosynthetic analysis.