Tunable copper complexes with functional ligands: A promising strategy for green primary explosives

Exploring alternatives of lead-containing primary explosives (lead azide, LA; lead styphnate, LS) has always been a pressing issue in the field of energetic materials. Although some lead-free primary explosives based on tetrazole have been reported, there are no qualified products that really replace LA. In this research, four energetic coordination polymers [Cu-3(ATZ)(2)(N-3)(6)](n) (CAA-1), [Cu(ATZ)(2)(N-3)(2)](n) (CAA-2) (ATZ = 4-amino-1,2,4-triazole), [Cu-2(IMI)(N-3)(4)](n) (CIA) (IMI = imidazole) and [Cu-3(2-MAT)(2)(N-3)(6)](n) (CMA) (2-MAT = 1-methyl-5-aminotetrazole) are synthesized via a mild method. Their molecular structures are confirmed by X-ray single crystal diffraction with fascinating 1D, 2D, and 3D frameworks. Thermal decomposition temperatures, sensitivities and the initiation capabilities of these compounds are measured in details. The results show that weak interaction effectively improves the stability of these compounds. The tunable ignition performances (minimum primary charge as 20 mg for CAA-1, 50 mg for CIA, 15 mg for CMA) and sensitivities can be tailored by different ligands. In particular, CAA-1 possesses an acceptable (172.2 degrees C) thermal stablility, sensitivity, excellent free-flowing property and micromorphology, it is thus employed for future commercial application tests. The detonating capabilities of three typical detonators using CAA-1 to replace lead azide are tested with excellent results.