Computational Screening of Metalloporphyrins for CO2 Activation

<p><span>Electrocatalytic CO₂ reduction (eCO₂R) to value-added chemicals offers a promising route for carbon capture and utilization. Metalloporphyrin (M-POR) is a class of catalysts for eCO₂R that has drawn attention due to its tuneable electronic and structural properties. This work presents a computational screening, based on density functional theory calculations, of one of the key steps in the eCO₂R: the adsorption of CO₂ on 110 M-PORs with varying peripheral ligands, metal centres, and oxidation states, to understand how these factors can influence CO₂ activation. A set of criteria was used to shortlist M-PORs that activate CO₂ based on their ability to lengthen the C&ndash;O bond, bend the O&ndash;C&ndash;O angle, bind CO₂, and donate charge from the metal centre of the M-POR to the carbon centre of CO₂. Based on defined criteria, such as binding energy, C&ndash;O bond elongation, O&ndash;C&ndash;O bending, and charge transfer, 16 systems were selected for their potential to activate CO₂. These systems predominantly have the electron configuration of the metal centre in the d⁶ and d⁷ configurations. These systems primarily have the electron configuration of the metal centre in d⁶ and d⁷ configurations. Natural Bond Orbital analysis revealed the impact of electron-withdrawing groups in the system, which increases orbital splitting and, consequently, lowers the ability of the M-POR to activate CO₂. Second-order perturbation theory analysis confirms that the presence of electron-donating groups in the ligand structure enhances CO₂ activation. This work demonstrates the interconnected effect of peripheral ligands, metal centers, and oxidation states in M-PORs on their ability to adsorb and activate CO2, thereby establishing structure-activity relationships within M-PORs.</span></p>