Boosting hydrogen transfer catalysis by symmetry breaking of iron site

Hydrogen transfer reactions hold pivotal importance in organic synthesis by enabling selective bond formation, achieving redox-neutral transformations, and advancing sustainable methodologies. However, designing efficient catalytic systems for such reactions under mild conditions persists as a fundamental challenge in green chemistry. In this study, we present a controllable synthesis of defective graphene-anchored iron single-atom catalysts (Fe₁-DG SACs) through a hydrothermal-etching strategy. Findings reveal that micron-sized metallic Fe precursors spontaneously evolve into Fe nanoparticles and anchored on DG (Fe_NPs-DG), whereas Fe(II) and Fe(III) precursors yield larger Fe₂O₃ nanoparticles, exhibiting an intrinsic oxidation resistance of metallic iron in the hydrothermal system. Subsequent HCl etching of Fe_NPs-DG generates well dispersed single Fe atoms with symmetry-broken Fe-N₄ coordination structure. Remarkably, the single-atom catalyst displays an identical catalytic efficiency to its nanosized counterpart (Fe_NPs-DG) in hydrazine-mediated hydrogen transfer reduction of nitroaromatics under ambient conditions, attaining a turnover frequency of 6095.1 h⁻¹ for p-nitrophenol reduction while maximizing metal utilization. Multidisciplinary characterizations and theoretical calculations demonstrate that the asymmetric Fe-N₄ configuration enables dual-function catalysis: simultaneously activating hydrazine dehydrogenation and steering selective hydrogen transfer to nitroaromatics. This work advances atomic-scale understanding of symmetry engineering in single-atom catalysts and establishes a green paradigm for hydrogen transfer reactions under mild condition.