Electronic Effect of Artificial Second‐Sphere Amide Pendants Affects the Electrochemical Reduction of CO ₂ by Iron Porphyrins

To design the molecular catalysts for the carbon dioxide reduction reaction (CO 2 RR) requires fine‐tuning both of electronic structure and second‐sphere interactions. Here, we modified two amide‐functionalized iron tetraphenylporphyrin ( FeTPP ) featuring ortho ‐substituted pendants, FeTCF 3 with an electron‐withdrawing trifluoromethyl group (─CF 3 ), and FeTCH 3 with an electron‐donating methyl group (─CH 3 ). These amide pendants provide hydrogen‐bonding capability to stabilize Fe‐CO 2 intermediates, while the electronic substituents tune the redox properties of the iron center. FeTCH 3 demonstrated lower overpotential ( η ) and higher maximum turnover frequency (TOF max ) compared to FeTPP , and FeTCF 3 exhibited the smallest overpotential ( η ), as expected. Moreover, water can be an eco‐friendly and effective proton source for the second‐sphere amide pendant porphyrins as catalysts during electrochemical CO 2 reduction reactions.