Ligand Denticity-Driven Structure–Activity Regulation: Performance Differences and Mechanisms of Ferrocene Mono-/Di-Hydrazone Copper Complexes in Catalyzing Ammonium Perchlorate Decomposition

Studying how ligand denticity regulates the catalytic activity of ferrocene hydrazone copper complexes in ammonium perchlorate decomposition, we synthesized mono-hydrazone (Fc-MH-Cu) and di-hydrazone (Fc-DH-Cu) complexes. The complexes were characterized by IR, XPS, SEM, BET, TG-DSC, and in situ TG-IR. Ligand denticity critically influences coordination mode, electronic structure, and morphology. Fc-MH-Cu forms a flexible chelating structure, lowering the electron cloud density of Cu²⁺ and enhancing electron transfer. Its small particle size, high dispersibility, and large pore size enhance AP adsorption, ClO₄- activation, and product diffusion. This leads to superior catalytic performance, reducing AP's decomposition peaks to 318 °C and 338 °C, with heat release of 1010 J/g and activation energy of 101.9 kJ/mol. In contrast, Fc-DH-Cu adopts rigid chelating coordination, increasing the Cu²⁺ electron density and limiting electron transfer. Its agglomerated morphology and small pore size hinder mass diffusion, resulting in inferior performance. In situ TG-IR revealed that Fc-MH-Cu promotes deep oxidation of NH₃ to NO₂ at 300–380 °C, whereas Fc-DH-Cu mainly produces N₂O above 340 °C. This work clarifies the role of ligand denticity in regulating the adsorption-activation-decomposition synergy, providing guidance for the design of high-efficiency AP catalysts.