Theoretical Mechanism Exploration of Highly Selective Reductive Amination of Furfural to Furfurylamine over a Single-Atom Ru1-N3/C Catalyst

Ru-N/C catalysts demonstrate good catalytic performance toward the reductive amination of furfural (FAL) to furfurylamine (FAM). However, its underlying catalytic mechanism remains unclear at the molecular level. In this study, a single-atom Ru-1-N-3/C surface was modeled, which can simultaneously activate NH3 and H-2 to an appropriate level. Over Ru-1-N-3/C, the catalytic mechanisms for the reductive amination of FAL to FAM, as well as the dimerization of FAM to difurfurylamine (DFAM), have been investigated theoretically in methanol solution at the GGA-PBE/DNP level. Molecular dynamic simulation results indicate the preferential adsorption of NH3 over Ru-1-N-3/C. The preferential activation of NH3 facilitates the formation of furfurylimine (FIM). However, the prior activation of H-2 leads to the formation of furfuryl alcohol (FOL), which hinders the production of FAM. The Ru-N-C group in the amination of FAL with FIM as an intermediate enhances the C-O bond cleavage more efficiently due to the nucleophilicity of the N atom. Lower temperatures are crucial for preserving FAM formation, whereas FAM undergoes dimerization with increasing temperature elevating kinetically. The current research results should provide some theoretical insights for designing highly selective catalytic systems toward the reductive amination of aldehydes/ketones.