N-bridged Zn-Ni dual-site single-atom catalysts: steering cascade transfer hydrogenation via site-specific synergy

The cascade synthesis of imines from alcohols and nitroarenes via catalytic transfer hydrogenation (CTH) is a highly sustainable process. However, developing efficient non-noble metal catalysts remains a formidable challenge due to the kinetic mismatch of sequential reaction steps and sluggish active hydrogen transfer. Herein, we propose a novel spatial functional partitioning catalyst design paradigm and construct a highly efficient diatomic catalyst featuring atomically dispersed ZnN 4 and NiN 4 sites spatially bridged by nitrogen atoms. Experimental and theoretical investigations reveal a precise dual-site cooperative mechanism of the unique Zn-N-Ni constructure. Specifically, the highly electron-deficient Zn sites (+1.14 |e| vs . +0.83 |e| of Ni) preferentially activate the hydroxyl group of benzylalcohol to generate active H* due to a lower dehydrogenation energy barrier (89.6 kJ mol −1 vs. 111.6 kJ mol −1 for Ni). Concurrently, the Ni sites, featuring a higher d -band center (–1.47 eV vs. –5.50 eV for Zn), facilitate nitrobenzene hydrogenation with a significantly lower barrier (73.7 kJ mol −1 ), while the bridging N serves as an H* adsorption site. Consequently, this synergistic configuration integrates single-atom efficiency with dual-site cooperation, achieving 96% nitrobenzene conversion and 90% imine selectivity. This work not only elucidates the atomic-level hydrogen transfer mechanism in cascade reactions but also establishes a rational design principle for complex tandem catalytic systems. Atomically dispersed ZnN 4 and NiN 4 sites linked by bridging N enable cooperative catalysis where Zn dehydrogenates alcohols and Ni extracts H from adjacent N-H for nitroarene hydrogenation toward imines. Download: Download high-res image (64KB) Download: Download full-size image