Fig. 1.

a Chemical structure of the Co-corrole. b Cyclic voltammetry of Co-corrole dissolved in CH₃CN under Ar (red). Two metal centered redox peaks at −0.5 V (Co (III)/Co(II)) and −1.5 V (Co(II)/Co(I)) vs. NHE could be identified. The irreversibility of the redox peak at −0.5 V is likely due to the partial loss of the PPh₃ ligand. Cyclic voltammetry of Co-corrole dissolved in CH₃CN under CO₂ (blue), in CH₃CN/H₂O (4:1) under Ar (pink) and in CH₃CN/H₂O (4:1) under CO₂ (black). c DFT optimized geometries of [Co-corrole]⁰, 1e⁻ and 2e⁻ reduced species showing the movement of Co center into the central cavity of the corrole ring with concomitant lengthening of the Co-PPh₃ bond upon successive reduction. d Kinetic isotpopic effect demonstrated by cyclic voltammetry of Co-Corrole (0.5 mM) recorded in CO₂ saturated in acetonitrile in the presence of varying amount of H₂O or D₂O. Linear dependence of i_cat/i_p on the concentration of water (analogous to plotting √k_CO2 vs. [water], KIE = k_CO2H/k_CO2D = (Slope_H2O/slope_D2O)² = (37.1057/28.7545)² = 1.67). All cyclic voltammograms were recorded with 0.1 M TBAPF₆ as supporting electrolyte using a glassy carbon as working electrode and a Ag/AgCl as reference electrode at a scan rate of 100 mV s⁻¹. e Heterogeneous catalysis of 1 mM Co-corrole on carbon-fiber electrode under Ar (black) and CO₂ (red) at pH = 6.0 (Ag/AgCl/KCl, Pt, 0.1 M NaClO₄, 100 mV s⁻¹)