Azido azole-1,3,4-triazine fused energetic materials: A bioinspired strategy for tuning thermal stability and sensitivity of metal-free primary explosives via hierarchical hydrogen-bond self-assembly

Primary explosives are useful but they usually pose low thermal stability and underlying safety threat to manufacturers and users. It is highly desirable yet challenging to develop next-generation primary explosives with lead-free, environmentally friendly, high-dense, thermostable and safe organic energetic materials for replacement. Here, inspired by biosystem's architecture, we report a simple and efficient hierarchical hydrogen-bond self-assembly strategy to synthesize high-performance primary explosives with enhanced thermal stability (Tonset > 200 °C) and decreased sensitivity (40 J). Owing to the above-efficient strategy, 7-azide-3-(1H-tetrazol-5-yl)-[1,2,4]triazolo[5,1-c] [1,2,4]triazin-4-amine-2- oxide (EM-4) and 7-azide-4-amino-3-nitro-[1,2,4]triazolo[5,1-c][1,2,4]triazine (EM-6) feature high densities of 1.825 and 1.816 g cm−3, much superior to their analogues 7-azide-3-(1H-tetrazol-5-yl)-[1,2,4]triazolo[5,1-c][1,2,4]triazin-4-amine (EM-3) and 8-azide-4-amino-3,7-dinitropyrazolo-[5,1-c][1,2,4]triazine (EM-9), comparable to that of 6-azido-8-nitrotetrazolo[1,5-b]-pyridazine-7-amine (ANTP). Meanwhile, EM-3 (Td = 225 °C), EM-4 (Td = 290 °C) and EM-6 (Td = 210 °C) exhibit better thermal stability and lower sensitivities (IS = 40 J) than those representative metal-free primary explosives (Td = 114–193 °C, IS = 0.25–17 J). The as-synthesized materials all feature superior performance to those of commercially scale-up and industrial applicable primary explosive 2-diazo-4,6-dinitrophenol (DDNP). Moreover, the calculated detonation velocity of EM-6 reaches up to 9029 m s−1, which is comparable to that of 6-nitro-7-azido-pyazol[3,4-d][1,2,3]triazine-2-oxide (ICM-103) but EM-6 features better thermal stability and safety performance. Bioinspired organic primary explosive may open a new gate for the design and development of more thermostable, higher dense and safer initiating substances towards future advanced applications.