Controlling the CO2 Reduction Reaction through Dual-Atom Catalysts Embedded in Expanded Porphyrins: A DFT Study

In the pursuit of innovative molecular catalysts for the electrocatalytic reduction of CO2, we employed computational methodologies to investigate six Cu-based ex- panded porphyrin dual-atom catalysts (DACs). Our study revealed both large and small variations among the different DACs. Despite metal center substitutions, the highly delocalized nature of the π orbitals in the expanded porphyrin complexes led to minimal differences between the frontier orbitals. Conversely, pronounced differences emerged during hydrogen reduction. Notably, the formation of H2 exhibited low limiting potentials ranging from 0.13 to 0.43 eV, attributable to the ligand-centered activity of the expanded porphyrin. Similar limiting potentials (< 0.31 eV) for CO2 reduction indicate competition between the two reduction processes. This can be attributed to the emergence of highly favorable bridging μ2 intermediates, exemplified by *OCHO and *OH. The preference for these intermediates is expected to lead to the formation of only 2e- and 4e- products, namely H2, HCOOH and H2CO. Specifically, CuFe and CuMn DACs are poised to favor CO2 reduction to produce HCOOH and H2CO, while CuCo, CuCu, and CuZn DACs are anticipated to favor the production of H2.