Efficient co-upcycling of glycerol and CO₂ into valuable products enabled by a bifunctional Ru-complex catalyst

Glycerol and CO2 are largely produced as by-products in modern industry. Herein, three Ru complexes bearing air- and water-stable NHC-nitrogen-nitrogen ligands are designed as bifunctional catalysts to upcycle glycerol and CO2 simultaneously. Among them, Ru complex 2 featuring an N-H structure shows the highest efficiency with TONs up to 300 000 and 387 000 for formate and lactate, respectively. C-13 labelling experiments clearly manifest that formate is primarily derived from CO2. Furthermore, in situ FTIR spectra suggest that glyceraldehyde from glycerol might serve as a key intermediate to form lactate, while DFT calculations indicate that Ru complex 2 possesses the lowest reaction barriers and can form the Ru = N intermediate, contributing to its higher activity.