Construction of Rh-N₄ single atoms and Rh clusters dual-active sites for synergistic heterogeneous hydroformylation of olefins with ultra-high turnover frequency

The design and construction of Rh-based heterogeneous catalysts with excellent catalytic activity and high atom utilization for hydroformylation of olefins is extremely important but still challenging. Herein, we report a robust dual-active sites coupling catalyst containing triphenyl phosphine-coordinated Rh clusters and Rh-N₄ single atomic sites (PPh₃-Rh_AC-SA/N-C) for hydroformylation of olefins. The PPh₃-Rh_AC-SA/N-C exhibits ultra-high activity to the hydroformylation of 1-hexene among the reported Rh-based catalysts, achieving the turnover frequency value of 6599 h⁻¹, which is 13-fold higher than that of conventional Wilkinson's catalyst (508 h⁻¹). Density functional theory calculations reveal that PPh₃-coordinated Rh clusters can facilitate the adsorption and activation of olefins and H₂. The adjacent Rh-N₄ provides a more favorable adsorption site for CO, enabling the easy addition of CO to carbon chain. The incorporated PPh₃ increases the electron cloud density of Rh clusters, reduces the energy barriers of hydrogenation step on Rh clusters, and thereby enhancing the activity of catalyst for hydroformylation. Furthermore, PPh₃-Rh_AC-SA/N-C can be applied as a recyclable catalyst without obvious deactivation. This work provides a novel design concept for the construction of dual sites coupling catalyst from the atomic scale for synergistic heterogeneous hydroformylation.