Synergistic modulation of metal Ru by defects and amino groups for efficient hydrogenation of aromatic amines

Green production of dicycloalicyclic amine is of great importance and faces significant challenges. At the same time, the addition of liquid alkali to prevent deamination and condensation is environmentally hazardous, and the hydrogenation of aromatic amines requires high temperature and pressure. In this study, a urea-assisted ball milling process was developed to prepare defect-rich boron nitride (d-BN) as a support for Ru/d-BN catalysts, enabling environmentally friendly and efficient hydrogenation of 4,4′-diaminodiphenylmethane (MDA) to produce alicyclic amines. As a result, exceptional activity was achieved with only 3.0 wt% Ru loadings on d-BN nanosheets at 130 °C and 3 MPa, reaching 100% MDA conversion and 99.6% selectivity of 4,4-diaminodicyclohexylmethane (PACM). Based on the correlation between the catalytic activities of defective sites, amino groups and active metal Ru clusters, combined with the results of defective site quenching experiments, electron paramagnetic resonance (EPR), X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD) and density functional theory (DFT) calculations, a synergistic interaction between the defects, amino groups and the metal Ru was proposed. The Ru/d-BN catalysts modulated the metal Ru at the Fermi energy level through the Ru–N and Ru–B bonds, which promoted the adsorption of MDA and desorption of the product PACM. Moreover, the d-BN support played a crucial role in metal particle dispersion and promoting hydrogen spillover. Stability evaluations and substrate experiments demonstrated the outstanding hydrogenation activity and robust stability of Ru/d-BN catalysts. Kinetic analysis revealed a reduced activation energy of 75.08 kJ/mol for the reaction, 50 kJ/mol lower than that of Ru/h-BN. • Urea-assisted ball milling gives rise to abundant boron defects on Ru/d-BN. • Defect sites and amino group enhances activation of aromatic amines with better interaction. • The Ru cluster site actively transfers electrons via Ru–B and Ru–N, modulating its energy to the Fermi level. • Fermi level Ru clusters are essential for activating aromatic rings. • Introduction of defect sites also promote hydrogen activation and spillover.