Homogeneous carbon dioxide reduction with p-block element-containing reductants

Carbon dioxide is abundant in nature. The reduction of carbon dioxide provides an attractive and alternative method for its utilization as a C1 building block. Compared to molecular hydrogen, carbon dioxide reduction using reductants containing p-block elements (especially E-H) requires much milder reaction conditions and gives diverse products. In this tutorial review, carbon dioxide reduction with various reductants containing p-block elements (E = B, Si, P, Al, Ga, Ge, Sn) other than H-2 are discussed and classified by the species in use. Value-added chemicals such as the corresponding formates, acetal, methoxide and methane are produced with the coproduction of E-O molecules/polymers. From another perspective, this type of reaction can also be deemed as the oxidation of main group compounds using CO2 as a soft oxidant or CO2 mediated dehydrogenative polymerization. We also discussed the preparation route for main group reductants and it is obvious that most of the main group hydrides are expensive to prepare and hard to handle at a large scale, thus work focusing on main group species other than CO2 transformation should be a promising direction.