Enhanced Regioselectivity in Propylene Hydroformylation Using Xantphos-modified Single-Atom Rh/CeO2 Catalyst

Single-atom Rh catalysts have been reported to exhibit high activity in olefin hydroformylation, yet with limited regioselectivity. We develop a Xantphos ligand coordinated single-atom Rh/CeO2 catalyst, which exhibits improved regioselectivity for butyraldehyde (n/i ratio equal to 13) while maintaining good activity (TOF = 476 h-1) in hydroformylation of propylene. The unique coordination environment created by Xantphos enhances steric hindrance at Rh active sites, thereby improving its regioselectivity for n-butyraldehyde. That is, two P atoms from a Xantphos ligand bind directly to Rh, while a P atom from another Xantphos attaches to an oxygen vacancy on CeO2 near Rh, achieving a P-Rh coordination number of 3. This unique structure shifts the propylene adsorption configuration from hybrid modes to the terminal mode, favoring n-butyraldehyde formation. The creation of electron-rich Rh sites with P/Rh ratio of 3 benefits the formation of Rh-H species for the ratedetermining step, thus showing commendable activity.