Computational mechanistic insights into homogenous catalytic carbon dioxide (CO 2 ) reduction using aluminium, gallium, and indium-based complexes

Due to the increasing global climate crisis, catalytic conversion of CO2 to value-added products is of importance. For this study, Density Functional Theory (DFT) calculations were performed to investigate the mechanism of CO2 reduction mediated by aluminium, gallium and indium metal complexes using B3LYP functional together with Grimme’s dispersion correction (GD3) and the 6-31+G(d,p) basis set. The polarisable continuum model (PCM) was employed as an implicit solvation model using tetrahydrofuran (THF) as the solvent, as implemented in the Gaussian 16 programme package. The results revealed that CO2 activation occurs through a metal to oxygen coordination due to more favourable orbital overlap. The pathways for the aluminium-based catalysts exhibit lower activation barriers (19.3 kcal/mol to 36.1 kcal/mol) compared to the other catalysts, making them the most kinetically favoured for activation. The catalysts give exergonic intermediate products with energies of −24.6 kcal/mol to −4.4 kcal/mol, indicating a spontaneous reaction. This comparative work provides valuable insight into CO2 activation and reduction to formic acid using environmentally friendly, non-toxic alternatives to transition metal-based catalysts, offering a more rational based approach for designing improved catalysts based on both kinetic and thermodynamic requirements.