Computational Investigation on Adsorption Facilitated Activation of CO ₂ on Fe _2–7 Clusters

In this article, we report a comprehensive computational investigation on the adsorption and activation of carbon dioxide (CO₂) on the surface of small iron clusters, Fe_n (<i>n</i> = 2-7). The adsorption process in each system was investigated following a two-dimensional potential energy surface (2D-PES) scans. The calculated adsorption energies range between -57 and -112 kJ mol^-1, indicating a strong and favorable binding. The most stable adsorption products were characterized with a bicoordinated bend CO₂ moiety with two Fe-C bonds on the edge of the clusters. All Fe_<i>n</i> clusters have shown a barrierless CO₂ adsorption process. The adsorption of CO₂ on the Fe_2-7 clusters resulted (a) ∼0.09 Å elongation of the CO bond lengths, (b) bending of the OCO bond angles ∼47°, (c) red-shifted ν_CO stretching frequencies ∼700 cm^-1 and (d) significant reduction of CO bond strength and order. The strong adsorption and high activation of CO₂ were attributed to charge transfer from the electron-rich iron clusters to the CO₂. The results revealed the applications of small metal clusters for barrierless adsorption and efficient activation of CO₂. These findings hold significance in the pursuit of efficient and economical catalytic processes for capturing and recycling CO₂, thereby contributing to a sustainable future.