Mechanistic Considerations in the Selective Thermocatalytic Activation of CO ₂

The thermocatalytic hydrogenation of CO 2 to value-added chemical products provides a readily accessible strategy for its valorization, but relies decisively on the control of selectivity to specific products of interest for the application under consideration. Selectivity control in this context will rely primarily on a mechanistic understanding of pathways for CO 2 hydrogenation, as well as the identity of kinetically relevant steps within each of these respective pathways. In this perspective, we provide a map of plausible pathways for the hydrogenation of CO 2 to three distinct products of interest–CO, methane, and methanol–and discuss mechanistic aspects of relevance to producing each of these molecules. Intentionally emphasized are the critical role of carbonyls, as well as the readily apparent ambiguity associated with differentiating between intermdiates that are active rather than spectating in nature. Also highlighted are descriptors for selectivity control, strategies for manipulating CO 2 activation, and the salient, multifaceted role of water in affording high rates and selectivity for this (re)emerging reaction system of commercial and scientific interest.