Formaldehyde Hydroformylation over a Heterogeneous Catalyst Based on Functionalized Rh-biphosphine Unit: A Combined Experiment and Theoretical Study

This work reports a functionalized SiO ₂ supported immobilized Rh catalyst for the heterogeneous hydrogenation of formaldehyde to glycolaldehyde (GA) without the need for additional soluble phosphine species such as triphenylphosphine. The catalyst was prepared through an effective strategy to anchor active rhodium carbonyl species to functionalized silica molecular sieves. The successful grafting of bisphosphine ligand and rhodium carbonyl was evident through FT-IR studies. The surface interactions between Rh species and P species were elucidated by ³¹ P MAS NMR and X-ray photoelectron spectroscopy (XPS) studies, showing that Rh species were anchored to the support via Rh-P bonds. And the coordination modes of Rh were changed by impregnation under different atmospheres. Compared to a nitrogen atmosphere, the active species HRh(CO) ₂ L, generated by impregnation in syngas atmosphere, showed better catalytic activity and lower leaching of the active metal. Furthermore, density functional theory (DFT) calculations were employed to elucidate the reaction mechanism, and the reasons underlying the differences in catalytic activity and metal leaching behavior among catalysts prepared under different atmospheres. These findings are significant for insights into the relation between the catalytic performance and structure.