Formaldehyde hydroformylation over a heterogeneous catalyst based on a functionalized rhodium-biphosphine unit

Hydroformylation is an important industrial process for aldehyde production, but the separation of homogeneous Rh catalysts and the leaching of active Rh species remain major challenges. Here we show a heterogeneous Rh catalyst for formaldehyde hydroformylation to glycolaldehyde (GA) based on immobilized rhodium carbonyl species anchored on functionalized SiO2. Spectroscopic characterization confirms that Rh species are stabilized through Rh-P interactions, while the coordination environment of Rh can be tuned by catalyst preparation atmosphere. The catalyst prepared under syngas atmosphere generates HRh(CO)2L species, exhibiting higher catalytic activity and significantly lower Rh leaching than that prepared under N2 atmosphere, without requiring additional soluble phosphine ligands. Density functional theory (DFT) calculations reveal the origin of the enhanced activity and stability by clarifying the reaction pathway and coordination stability of the active species. These findings provide insights into the structure-performance relationship of heterogeneous Rh catalysts for formaldehyde hydroformylation. The immobilization of rhodium species on silica-based materials is an effective strategy for the development of heterogeneous catalysts for formaldehyde hydroformylation, but its reliance on triphenylphosphine makes product separation and catalyst recycling difficult. Here, the authors report a strategy to produce a functionalized, SiO2-supported, immobilized rhodium catalyst in which the introduction of bis[2-(diphenylphosphino)ethy]amine as an electronic donor through grafting technology removes the need for implementing triphenylphosphine to enhance catalytic performance.