Tandem Switch-Triggered On-Demand Synthesis of Aromatic Amines in High Yields

Tandem catalysis stands as a beacon of chemical sustainability. Although bifunctional catalysts have achieved wide success in two-step tandem reactions, achieving multi-step catalysis with three or more distinct and potentially incompatible catalytic sites and components remains an ambitious challenge. Here, we present a "tandem switch" strategy that transforms these incompatibilities into functional advantages, enabling on-demand production of primary, secondary, and tertiary aromatic amines, all with yields exceeding 96 %. A kinetic switch, enabled by phosphotungstic acid functionalization of the Ni-Ni(Al)O heterojunction catalyst, modulates the Ni-Ni and Ni-O boundary microenvironment to simultaneously accelerate the rate-determining steps in nitrobenzene hydrogenation, N-alkylation, and aza-Michael addition. Meanwhile, a thermodynamic switch, controlled by the competitive adsorption of ethanol, hydrogen, and acrylonitrile, stepwise minimizes Gibbs free energy to ensure a seamless reaction cascade. Hence, by toggling these tandem switches on or off, we achieve selective regulation of nitrobenzene conversion pathways into the production of targeted aromatic amine. Techno-economic analysis shows the developed process significantly reduces material and energy consumption for sustainable amine production.