Enhanced tandem hydrogenation of nitroaromatics to alicyclic amines via Pt-Ru synergistic catalysis

Green production of alicyclic amines is highly desirable but of great challenges. Herein, an efficient one-pot synthesis of alicyclic amines from nitroaromatics was realized with a Pt-Ru bimetallic catalyst. 0.5 %Pt-2.5 %Ru supported on an air-exfoliated C3N4 nanosheet achieved 100.0 % conversion of nitrobenzene (NB) with 98.9 % selectivity of cyclohexylamine (CHA) under mild conditions of 80 °C and 1 MPa, attaining a yield rate for alicyclic amine of 357.9 mmol/gmetal·h. Our study has shown hydrogenation of nitro group and aromatic ring took place in sequence over Pt and Ru in a tandem manner due to the highly selective adsorption. During the hydrogenation, the homolytic dissociation of H2 occurred on the bimetal sites and the inter-site hydrogen spillover between the bimetal played a crucial role. C3N4 nanosheet as the support not only gave rise to the uniform dispersion of metal nanoparticles, but was crucial in curbing the unnecessary adsorption of intermediate aromatic amines. Our study has also demonstrated the good stability and wide applicability of the Pt-Ru/C3N4-air catalyst for the hydrogenation of various nitroaromatic derivatives.