Mechanistic Study of CO₂−Ethylene Coupling to Form Acrylic Acid on N₃M–MN₃ Dimer Anchored onto Defective Graphene

Coupling CO2 with ethylene to produce acrylic acid is valuable for manufacturing various industrial fine chemicals. Currently, this reaction is catalyzed by transition metal molecular complexes, which show low activity, limiting their industrial application. Therefore, the development of highly active heterogeneous catalysts for this reaction is desirable. Herein, metal dimers introduced into graphene are assessed as heterogeneous catalysts for the CO2-ethylene coupling reaction using density functional theory calculations. It is found that Pd, Rh, Ni, and Cu dimers facilitate the βH transfer steps, whereas Zn, Ru, and Os facilitate the CC coupling steps. The variation of the overall energetic barrier based on the energetic span model is rather narrow, as these two elementary steps are anticorrelated with each other. Furthermore, the stability of metallalactones is found to be a key descriptor for the activation energies of both the CC coupling and the βH transfer steps. Using Crystal Orbital Hamilton Population analysis, it is identified that the strength of the CβCγ bond in metallalactones can serve as an electronic-level descriptor for activation energies. It is anticipated that the insights gained from this study will guide the development of heterogeneous catalysts for the CO2-ethylene coupling for producing acrylic acid.