Efficient light-driven reductive amination of furfural to furfurylamine over ruthenium-cluster catalyst

Selective reductive amination of carbonyl compounds with high activity is very essential for the chemical and pharmaceutical industry, but scarcely successful paradigm was reported via efficient photocatalytic reactions. Herein, the ultrasmall Ru nanoclusters (∼0.9 nm) were successfully fabricated over P25 support with positive charged Ruδ+ species at the interface. A new route was developed to achieve the furfural (FAL) to furfurylamine (FAM) by coupling the light-driven reductive amination and hydrogen transfer of ethanol over this type catalyst. Strikingly, the photocatalytic activity and selectivity are strongly dependent on the particle size and electronic structure of Ruthenium. The Ruδ+ species at the interface promote the formation of active imine intermediates; moreover, the Ru nanoclusters facilitate the separation efficiency of electrons and holes as well as accelerate the further hydrogenation of imine intermediates to product primary amines. In contrast Ru particles in larger nanometer size facilitate the formation of the furfuryl alcohol and excessive hydrogenation products. In addition, the coupling byproducts can be effectively inhibited via the construction of sub-nanocluster. This study offers a new path to produce the primary amines from biomass-derived carbonyl compounds over hybrid semiconductor/metal-clusters photocatalyst via light-driven tandem catalytic process.