Computational Screening of Metalloporphyrins for CO2 Activation

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–O bond, bend the O–C–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–O bond elongation, O–C–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.