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

Haley A Petersen; Abdulaziz W Alherz; Taylor A Stinson; Chloe G Huntzinger; Charles B Musgrave; Oana R Luca

doi:10.1016/j.isci.2022.103997

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

iScience. 2022 Mar 3;25(4):103997. doi: 10.1016/j.isci.2022.103997. eCollection 2022 Apr 15.

Authors

Haley A Petersen¹, Abdulaziz W Alherz², Taylor A Stinson¹, Chloe G Huntzinger¹, Charles B Musgrave^{1

2

3}, Oana R Luca¹

Affiliations

¹ Department of Chemistry and Renewable and Sustainable Energy Institute, University of Colorado Boulder, Boulder, CO 80309, USA.
² Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309, United States.
³ Materials Science and Engineering Program, University of Colorado, Boulder, CO 80309, United States.

Abstract

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 ( $Δ G_{b i n d}$ ). Through synergistic experiments and computations, this study establishes a three-parameter correlation described by the equation $Δ G_{b i n d} = - 0.78 p K_{a} + 4.28 E_{r e d} + 20.95$ 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 $Δ G_{b i n d}$ 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 $Δ G_{b i n d}$ 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: Applied chemistry; Chemistry; Computational chemistry; Electrochemistry; Theoretical chemistry.