CO binding at Iron porphyrins: Reflecting on Heme model complexes to guide future electrocatalyst design

Area of Science:

• Electrochemistry and catalysis
• Materials science for energy applications
• Coordination chemistry of iron porphyrins

Background:

• Homogeneous electrocatalytic reduction of carbon dioxide (CO2) to products beyond carbon monoxide (CO) or formate is challenging.
• Iron porphyrins are promising catalysts, but their efficiency hinges on understanding carbon monoxide (CO) binding intermediates.
• Historical studies of iron porphyrins in hemoproteins provide foundational knowledge on CO/O2 discrimination and binding factors.

Purpose of the Study:

• To review structure-property relationships governing CO binding to Fe porphyrins for enhanced CO2 electrocatalysis.
• To evaluate how primary coordination sphere modifications influence CO affinity and activation.
• To explore how secondary coordination sphere design can promote productive CO binding and activation in CO2 reduction.

Main Methods:

• Literature review of synthetic and biological Fe porphyrin systems.
• Analysis of electronic tuning and axial ligation effects on CO affinity.
• Examination of second coordination sphere interactions for catalytic improvement.

Main Results:

• Primary coordination sphere modifications (electronic and axial ligation) significantly impact CO affinity and activation at Fe porphyrin sites.
• Second coordination sphere interactions offer design principles to further enhance productive CO binding and activation.
• Re-evaluation of existing literature through the lens of modern electrocatalyst development is crucial.

Conclusions:

• Understanding and manipulating CO binding to Fe porphyrins is key to advancing homogeneous CO2 reduction.
• Design principles from both synthetic and biological systems can guide the development of improved Fe porphyrin electrocatalysts.
• This review aims to support researchers in achieving efficient CO2 electrocatalytic reduction beyond CO.