A catalytic cascade
system for CO2 hydrogenation to
MeOH under acidic conditions is described. The reaction uses three
catalysts which promote stepwise formation and conversion of formic
acid and formate ester intermediates. The activities and decomposition pathways of different catalyst
candidates for each step were investigated. The combination Ru(H)2[P(CH2CH2PPh2)3]/Sc(OTf)3/Ir(tBuPCP)(CO) was found to be the
most active for CO2 hydrogenation to MeOH. An overall TON
of 428 was achieved after 40 h at 155 °C in EtOH, resulting in
a high concentration of MeOH (1.07 M). Catalyst speciation studies
upon completion of the reaction indicated that the carbonyl complexes
[Ru[P(CH3CH2PPh2)3](H)(CO)](OTf),
Ir(tBuPCP)(H)(CO)(OTf), and [Ir(tBuPCP)(H)(CO)2](OTf) were formed as the major metal-containing species.
Notably, [Ru[P(CH3CH2PPh2)3](H)(CO)](OTf) was found to be inactive for CO2 hydrogenation,
limiting the productivity of the reaction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.