Predictive energetic tuning of C-Nucleophiles for the electrochemical capture of carbon dioxide

Abstract

Summary: This work maps the thermodynamics of electrochemically generated C-nucleophiles for reactive capture of CO2. We identify a linear relationship between the pKa, the reduction potential of a protonated nucleophile (Ered), and the nucleophile’s free energy of CO2 binding (ΔGbind). Through synergistic experiments and computations, this study establishes a three-parameter correlation described by the equation ΔGbind=−0.78pKa+4.28Ered+20.95 for a series of twelve imidazol(in)ium/N-heterocyclic carbene pairs with an R2 of 0.92. The correlation allows us to predict the ΔGbind of C-nucleophiles to CO2 using reduction potentials or pKas of imidazol(in)ium cations. The carbenes in this study were found to exhibit a wide range CO2 binding strengths, from strongly CO2 binding to nonspontaneous. This observation suggests that the ΔGbind of imidazol(in)ium-based carbenes is tunable to a desired strength by appropriate structural changes. This work sets the stage for systematic energetic tuning of electrochemically enabled reactive separations.

Keywords

• Chemistry
• Theoretical chemistry
• Electrochemistry
• Computational chemistry
• Applied chemistry