Decoupling Electron and Proton Transfer in Noncontact Catalytic Hydrogenation of Nitroaromatics

A noncontact catalytic system is constructed by modifying metal nanoparticles supported on conductive carbon with (hypo)phosphorous acid. This design effectively prevents the adsorption of unsaturated substrates while permitting H2 activation to generate electrons and protons. The hydrogenation is governed by electron transfer processes, which occur at carbon support surfaces and ligand/support‐metal interfaces, with protons transferred via protic solvents. Abstract Understanding the elementary reactions of active hydrogen species and electron transfer mechanisms during catalytic hydrogenation remains a fundamental challenge. This work elucidates electron and proton transfer pathways in nitroaromatics hydrogenation using a noncontact catalytic system. Strong coordination of (hypo)phosphorous acid on Pt/Pd surfaces prevents substrate adsorption while permitting H2 activation, generating electrons retained on the catalyst and protons solvated in protic solvents. Hydrogenation proceeds via sequential reduction (nitro to nitroso and then to hydroxylamine), governed primarily by electron transfer through conductive carbon supports and secondarily via catalyst interfaces, while proton transfer occurs through protic solvents. Disproportionation dominates hydroxylamine conversion due to its kinetic superiority over direct hydrogenation. By applying these mechanistic insights, the system is expanded to diverse catalysts, demonstrating that hypophosphorous acid‐modified commercial Pt/C catalyst achieves efficient nitroaromatics hydrogenation. Remarkably, this approach functionally mimics enzymatic catalysis, enabling selective hydrogenation of coenzyme Q10 and its analogues. This study advances fundamental understanding of hydrogenation mechanisms of nitroaromatics, carbon‐supported catalyst design, and enzyme‐mimetic catalysis development. A noncontact catalytic system is constructed by modifying metal nanoparticles supported on conductive carbon with (hypo)phosphorous acid. This design effectively prevents the adsorption of unsaturated substrates while permitting H 2 activation to generate electrons and protons. The hydrogenation is governed by electron transfer processes, which occur at carbon support surfaces and ligand/support-metal interfaces, with protons transferred via protic solvents. Abstract Understanding the elementary reactions of active hydrogen species and electron transfer mechanisms during catalytic hydrogenation remains a fundamental challenge. This work elucidates electron and proton transfer pathways in nitroaromatics hydrogenation using a noncontact catalytic system. Strong coordination of (hypo)phosphorous acid on Pt/Pd surfaces prevents substrate adsorption while permitting H 2 activation, generating electrons retained on the catalyst and protons solvated in protic solvents. Hydrogenation proceeds via sequential reduction (nitro to nitroso and then to hydroxylamine), governed primarily by electron transfer through conductive carbon supports and secondarily via catalyst interfaces, while proton transfer occurs through protic solvents. Disproportionation dominates hydroxylamine conversion due to its kinetic superiority over direct hydrogenation. By applying these mechanistic insights, the system is expanded to diverse catalysts, demonstrating that hypophosphorous acid-modified commercial Pt/C catalyst achieves efficient nitroaromatics hydrogenation. Remarkably, this approach functionally mimics enzymatic catalysis, enabling selective hydrogenation of coenzyme Q10 and its analogues. This study advances fundamental understanding of hydrogenation mechanisms of nitroaromatics, carbon-supported catalyst design, and enzyme-mimetic catalysis development. Advanced Science, Volume 12, Issue 43, November 20, 2025.