Ultrastable 3V-PPh₃ polymers supported single Rh sites for fixed-bed hydroformylation of olefins

The heterogenization of homogeneous catalysts is of critical importance for both fundamental research and practical applications. The key obstacle to industrial applications of heterogenized homogeneous catalysts is the long-term stability of the immobilized molecular complexes. We unambiguously demonstrate in this report that the vinyl-functionalized PPh₃ polymers supported single Rh sites (Rh/POL-PPh₃) catalyst provided not only excellent catalytic activity but also ultrahigh stability for fixed-bed olefins hydroformylation, which is one of the most important industrial homogeneous catalytic processes for the synthesis of aldehydes and alcohols. HAADF-STEM and EXAFS results indicated that the Rh atoms were present in single Rh sites which were strongly coordinated with the exposed phosphorous atoms of the POL-PPh₃ support. The Rh/POL-PPh₃ catalyst provided high activity and selectivity because it maintained the catalytic functionalities similar to the homogeneous HRh(CO)(PPh₃)₃ complex, as demonstrated both by ³¹P MAS NMR and in situ FT-IR experiments. Thus a reaction mechanism, similar to that over the homogeneous HRh(CO)(PPh₃)₃ complex, was proposed for olefin hydroformylation over the novel Rh/POL-PPh₃ catalyst.