Efficient Generation of Negative Hydrogen with Bimetallic-Ternary-Structured Catalysts for Nitrobenzene Hydrogenation

Transition metal-catalyzed transfer hydrogenation (TH) with in situ negative hydrogen (H^-) has received extensive attention as an alternative to conventional high-pressure hydrogenation processes. However, the insufficient activity of hydrogen production and unclear the conversion process of hydrogenation remain a great challenge. In this work, brand new bimetallic ternary-structured catalysts (Ru_1+nM₁-TiO₂, M=Co, Cu, Fe, Ni) were synthesized to efficiently generate H^- donors from ammonia borane (AB, NH₃BH₃) for nitrobenzene hydrogenation under moderate conditions. The Ru_1+nCo₁-TiO₂ catalysts exhibited highest activity for hydrogen production form AB hydrolysis with a TOF value of 2716 min^-1. The Ru_1+nCo₁-TiO₂ achieved >90 % yields within 3-4 hours in converting nitrobenzene to anilines using AB. Mechanistic studies revealed that the high hydrolysis activity was due to that the Ru SA and Co SA sites of the bimetallic-ternary-structured catalyst required the lowest energy for the activation of AB and H₂O, respectively. Remarkably, the Co SA and Ru clusters exhibited an obvious synergistic effect in the TH process, which promoted the tandem hydrogenation of nitroaromatics. This work demonstrated an efficient approach to generate H^- donor with bimetallic-ternary-structured catalysts in TH process and further provided new inspiration on the development of multifunctional catalysts.