Highly dispersed Ru cluster-embedded nitrogen-doped hollow carbon spheres with tunable electronic properties for efficient catalytic reductive amination of biomass-derived furfural

Abstract

The catalytic reductive amination of biomass-derived carbonyl compounds into value-added primary amines has attracted significant attention in renewable biomass upgrading. Herein, highly dispersed Ru cluster-embedded nitrogen-doped hollow carbon sphere (Ru@NHCS) catalysts were constructed, which achieved a 100% furfurylamine (FUA) yield, and exhibited a superior initial reaction rate of 3745.7 mmol g_Ru⁻¹ h⁻¹ and a turnover frequency of 378.58 h⁻¹ in the reductive amination of biomass-derived furfural. Systematic structural characterization indicated that the presence of abundant N species promoted the uniform dispersion of Ru clusters and induced electronic metal–support interaction (EMSI) between Ru and the NHCS support, thus leading to the formation of bifunctional Ru⁰ and Ru^δ+ active sites. The structure–activity relationship study demonstrated that the synergistic catalysis of Ru⁰ and Ru^δ+ active sites effectively promoted the adsorption and activation of H₂ and NH₃ molecules, and accelerated the hydrogenation of imines and the ammonolysis of Schiff base intermediates, thereby achieving the highly selective synthesis of FUA under mild reaction conditions. Moreover, the Ru@NHCS catalyst exhibited excellent catalytic stability over five consecutive cycles and showed wide substrate applicability for the synthesis of valuable primary amines. This work not only unveils rational design strategies for developing efficient and stable metal catalysts to achieve the highly selective synthesis of value-added primary amines but also provides essential theoretical guidance for efficient biomass conversion.