Homogeneous Reduction of Carbon Dioxide with Hydrogen

Carbon dioxide (CO₂), a key greenhouse gas produced from both anthropogenic and natural sources, has been recently considered to be an important C1 building-block for the synthesis of many industrial fuels and chemicals. Catalytic hydrogenation of CO₂ using a homogeneous system is regarded as an efficient process for CO₂ valorization. This approach leads to the direct products including formic acid (HCOOH), carbon monoxide (CO), methanol (MeOH), and methane (CH₄). The hydrogenation of CO₂ to CO followed by alkene carbonylation provides value-added compounds, which also avoids the tedious separation and transportation of toxic CO. Moreover, the reduction of CO₂ with H₂ in the presence of amines is of significance to attain fine chemicals through catalytic formylation and methylation reactions. The synthesis of higher alcohols and dialkoxymethane from CO₂ and H₂ has been demonstrated recently, which opens access to new molecular structures using CO₂ as an important C1 source.