Shape-Selective Zeolites for Tandem CO₂ Hydrogenation-Carbonylation Reactions

The valorization of carbon dioxide as a C1 building block in C-C bond forming reactions is a critical link on the road to carbon-circular chemistry. Activation of this inert molecule through reduction with H₂ to carbon monoxide in the reverse water-gas shift (RWGS) reaction can be followed by a wide spectrum of consecutive carbonylation reactions, but the RWGS is severely equilibrium limited at the moderate temperatures of carbonylations. Here we successfully reconcile both reactions in one pot, while avoiding incompatibilities through a zeolite-based compartmentalized approach. More specifically, Pt encapsulated in a small-pore LTA zeolite selectively generates carbon monoxide in mild reaction conditions; an ensuing one-pot carbonylation reaction allows to shift the equilibrium through continuous consumption of CO. Moreover, the zeolite encapsulation avoids undesired reactions like hydrogenation of the olefin reactant through a molecular sieving effect. This strategy was first studied in-depth for Rh-catalyzed olefin hydroformylation with CO₂/H₂, affording aldehydes in good yields with high regioselectivities. The methodology was then extended to a variety of carbonylations using CO₂ for the synthesis of bulk and fine chemicals.