Dynamic Modulation of H· to H^-&H⁺ Enabled by Chemical Looping for Hydrogenation-Dehydrogenation Tandem Reaction

Coupling hydrogenation and dehydrogenation is of great significance, as both are pivotal bond reconstruction modes and co-occur in about 10% of chemical syntheses. However, stoichiometric imbalance often necessitates exogenous hydrogen, which causes "seesaw effect" and inhibits dehydrogenation, challenging thermodynamics and kinetics of tandem process. Herein, we propose a dynamic strategy based on chemical looping to modulate hydrogen species. We designed Ru_n@NiCu-V_M catalyst with metal vacancy (V_M) induced "electron allocator" properties, enabling reversible electron capture and release via chemical looping, which drives the neutral H· to convert into H^-&H⁺, while simultaneously completing electron cycling. The converted H^-&H⁺ promote hydrogenation of polar ─C═N bonds in the tandem reaction of 5-hydroxymethylfurfural to 2,5-furandimethanamine, while neutral H· enhances the dehydrogenation rate by avoiding charge repulsion with H^-&H⁺ generated from dehydrogenation of ─CH₂OH. The coupled hydrogenation-dehydrogenation process achieves a 1.7-fold rate enhancement, delivers 92% 2,5-furandimethanamine yield, outperforms most reported catalysts, and exhibits broad substrate applicability.