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

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

Haley A Petersen  1 , Abdulaziz W Alherz  2 , Taylor A Stinson  1 , Chloe G Huntzinger  1 , Charles B Musgrave  1   2   3 , Oana R Luca  1
Affiliations

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

Haley A Petersen et al. iScience. .

Abstract

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 (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 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 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.

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Conflict of interest statement

The authors declare no competing interests.

Figures

None
Graphical abstract
Scheme 1
Scheme 1
Reactions of imidazolium cations Generation of NHCs (Im) from their imidazolium precursors (A and B) and Im binding to CO2 (C) along with the three properties associated with these reactions: (A) Ered, (B) pKa, and (C) ΔGbind. R1 and R2 substituents are described in Figure 1.
Figure 1
Figure 1
Imidazol(in)ium-based NHCs used in the correlation studies Structures of each compound under study. See also Figure S1 and Table S1 for applicable experimental values associated with each NHC. Imidazolium counterparts (protonated NHCs) are abbreviated as "NHC"H in this work.
Figure 2
Figure 2
Linear correlations of pKa, free energy of CO2 binding, and reduction potential The three linear two-way correlations of (left) reduction potential and pKa, (middle) free energy of CO2 binding and pKa, and (right) reduction potential and free energy of CO2 binding for the compounds under study. Optimized molecular coordinates are available in Data S1.
Figure 3
Figure 3
3D correlation provides greater predictive power for estimating the free energy of CO2 binding Three-parameter linear relationship providing stronger correlation between Ered, pKa, and ΔGbind for the compounds under study
See this image and copyright information in PMC

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