Computational assessment of direct CO2 hydrogenation catalyzed by iron porphyrin

Carbon dioxide (CO₂) emissions drive climate change, demanding innovative capture and conversion strategies. Catalytic hydrogenation using affordable and abundant catalysts offers a promising route. Using density functional theory, we evaluated iron porphyrins as potential promoters of CO₂ hydrogenation, focusing on the reaction mechanism and the influence of iron oxidation and spin states. Our analysis reveals that the H₂splitting step promoted by Fe²⁺-porphyrin presents the highest barrier in the whole mechanism, yet it remains accessible. The Fe³⁺-porphyrin appears to be more efficient, affording lower barriers. Additionally, a base as cocatalyst is required during the H₂splitting step, while the presence of the conjugate acid of this base is energetically unfavorable when present in the following step, which is the hydride transfer to CO₂. Thus, our calculations suggest that iron porphyrins can effectively promote CO₂ hydrogenation.