Combining Low-Pressure CO₂ Capture and Hydrogenation to Form Methanol

This paper describes a novel approach to CO₂ hydrogenation, in which CO₂ capture with aminoethanols at low pressure is coupled with hydrogenation of the captured product, oxazolidinone, directly to MeOH. In particular, (2-methylamino)ethanol or valinol captures CO₂ at 1-3 bar in the presence of catalytic Cs₂CO₃ to give the corresponding oxazolidinones in up to 65-70 and 90-95% yields, respectively. Efficient hydrogenation of oxazolidinones was achieved using PNN pincer Ru catalysts to give the corresponding aminoethanol (up to 95-100% yield) and MeOH (up to 78-92% yield). We also have shown that both CO₂ capture and oxazolidinone hydrogenation can be performed in the same reaction mixture using a simple protocol that avoids intermediate isolation or purification steps. For example, CO₂ can be captured by valinol at 1 bar with Cs₂CO₃ catalyst followed by 4-isopropyl-2-oxazolidinone hydrogenation in the presence of a bipy-based pincer Ru catalyst to produce MeOH in 50% yield after two steps.