Hydrogen bond promotion for CO2 activation in homogeneous catalytic systems

The development of new, more efficient, and selective ways to activate CO2 for its transformation into value-added chemicals is a crucially important field of research aimed at finding viable alternatives to its uncontrolled atmospheric release. Among various kinds of covalent and noncovalent modes of catalyst-substrate interactions, the activation of reaction substrate via H-bond donors has risen to a prominent place in modern catalysis, especially through the concomitant development of organocatalysis. Although earlier examples of CO2 activation by H-bond donors trace back to several decades ago, it is only in recent years that this field has started receiving significant attention. Therefore, in this work, after a brief overview of the role of H-bond interactions in catalysis and on the noncatalytic interactions between H-bond donors and CO2, we review the crucial advances in the activation of CO2 by H-bond donors by considering both organocatalytic and metal-based transformations with the first being generally nonreductive in nature, and the latter generally concerning CO2 reduction to formates and CO. Particular attention is dedicated to the mechanistic understanding of such transformations as developed in the original manuscripts via control experiments, spectroscopy, and theoretical approach. We show herein that H-bond interactions often represent a pivotal tool to coordinate and activate CO2 and that a wide range of opportunities exists to further develop this field.