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

This work maps the thermodynamics of electrochemically generated C-nucleophiles for reactive capture of CO2. We identify a linear relationship between the pK(a), the reduction potential of a protonated nucleophile (E-red), and the nucleophile's free energy of CO2 binding (Delta G(bind)). Through synergistic experiments and computations, this study establishes a three-parameter correlation described by the equation Delta G(bind) = 0:78pK(a) + 4:28E(red) + 20:95 for a series of twelve imidazol(in)ium/N-heterocyclic carbene pairs with an R-2 of 0.92. The correlation allows us to predict the Delta G(bind) of C-nucleophiles to CO2 using reduction potentials or pK(a)s 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 Delta G(bind) of imidazol(in)ium-based carbenesis tunable to a desired strength by appropriate structural changes. This work sets the stage for systematic energetic tuning of electrochemically enabled reactive separations.