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 (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 pK_as 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.