Electronic structure tuning of cobalt porphyrins via meso-site substituent engineering for selective CO2 electroreduction.

Selective aqueous CO2 reduction is limited by hydrogen evolution. Three cobalt porphyrins with distinct meso-site substituents were synthesized and immobilized on carbon nanotubes. The benzene-substituted CoPh/CNT delivered >92% CO faradaic efficiency. Theoretical studies reveal that moderate electronic effects of the substituents balance CO2 binding and CO release, offering a catalyst design principle.