Energetic transition metal coordination compounds as efficient catalysts for rapid and concentrated decomposition of AP and RDX

Two novel energetic metal coordination compounds, Mn(VIM)₆(BF₄)₂ (Mn-VBF) and Ni(VIM)₆(BF₄)₂ (Ni-VBF), were synthesized as potential combustion catalysts for solid propellants, using 1-vinylimidazole (VIM) as the ligand and transition metals (Mn, Ni) as central ions . Physicochemical characterization confirmed their excellent safety characteristics (IS > 40 J, FS > 360 N) and favorable energetic properties. Their catalytic effects on the thermal decomposition of AP and RDX, as well as on the combustion of AP/RDX-based composites, were systematically studied. Both compounds concurrently catalyzed the decomposition of AP and RDX, lowering their decomposition temperatures and activation energies, and leading to a more concentrated and rapid heat release. Key experimental results show that Mn-VBF and Ni-VBF reduce the high-temperature decomposition peak of AP by 26.2 °C and 22.2 °C, narrow its peak width by 22.2 °C and 20.6 °C, and decrease the apparent activation energy by 73.8kJ·mol⁻¹ and 64.4 kJ·mol⁻¹, respectively. For RDX, the main decomposition peak is lowered to 233.6 °C and 236.2 °C, with activation energies reduced to 147.8kJ·mol⁻¹ and 153.9kJ·mol⁻¹. In AP/RDX-based composites, these catalysts shorten the burn time from 74 s to 39 s (Mn-VBF) and 44 s (Ni-VBF) while increasing flame intensity. Quantum chemical calculations, including frontier orbital analysis, reveal that the lower energy gaps (ΔE) for both α-spin and β-spin electrons in Mn-VBF underlie its enhanced catalytic performance relative to Ni-VBF. These findings highlight Mn-VBF and Ni-VBF as promising high-performance combustion catalysts for solid propellants.