Advances in CO2 capture and utilization: the role of DFT in understanding CO2 activation and its conversion mechanisms for methanol and cyclic carbonates production

As the amount of CO₂ gas in the atmosphere is significantly increasing, leading to profound global climate changes, growing attention has been addressed to CO₂ capture and utilization (CCU) processes, in which CO₂ is captured from the atmosphere and used as an abundant and non-toxic building block for the production of added-value products. Two main approaches to convert CO₂ into fuels and fine chemicals have been considered: reductive conversions in which the carbon atom is reduced to its lower oxidation states, and non-reductive processes, where the +4 oxidation state of carbon in CO₂ is maintained. However, due to the high stability of this inert molecule, both reductive and non-reductive conversions are only possible upon utilization of a proper catalyst. Although the research focus on CCU strategies has been widely spreading, there is still a lack of a comprehensive understanding of the mechanism of CO₂ conversion reactions, which is mainly due to the complexity of such conversion processes under reaction conditions. In this context, the contribution of quantum chemical investigations, particularly those based on density functional theory (DFT) calculations, have been of paramount importance to assist traditional experimental methods in a synergic combination able to boost the advancement in the missing knowledge. Based on those considerations, in this review we aim at discussing two main aspects of the CCU process. We will first focus on the importance of CO₂ activation, pointing out how DFT investigations help provide crucial insights into the activation strengths. Moreover, we will discuss the contribution of DFT to the understanding of the reaction conversion mechanisms, with a specific focus on two main products: methanol and cyclic carbonates. Eventually, current limitations and future perspectives will be briefly discussed.