Catalytic hydroformylation of alkenes to branched aldehydes promoted by water on Rh nanoclusters-anchored porous triphenylphosphine frameworks

The highly selective catalytic hydroformylation of alkenes to produce aldehydes is an important reaction in the chemical industry. While the recycling of the currently used homogeneous catalysts is complex, and the heterogeneous catalysis system with high catalytic performance for alkenes hydroformylation is highly desired. Herein, uniformly dispersed rhodium (Rh) nanoclusters with an average diameter of 1.04 nm confined in a triphenylphosphine group-based hyper-cross-linked polymer (HCP-PPh3) was fabricated. The obtained Rh(1.2 %)-HCP-PPh3 catalyst is very active for selective hydroformylation of alkenes. The electron and spatial effects of the phosphine ligand in conjunction with the solvation of water rendered high selectivity to the Rh nanocluster catalyst for the formation of the branched aldehydes by alkenes hydroformylation. Mechanism study revealed that the activation energy of the initial step of branched path (10.7 kCal/mol) was significantly lower than that of liner path (22.5 kCal/mol), leading to the high hydroformylation selectivity for branched aldehydes on Rh-HCPPPh3 catalyst. Thus, this study provides a novel and facile strategy for precisely designing Rh nanocluster-based catalysts that exhibits potential practical application in selective hydroformylation of alkenes to branched aldehydes in fine chemical industry.