Substitution of Nitrogen-Rich Linkers with Insensitive Linkers in Azide-Based Energetic Coordination Polymers towards Safe Energetic Materials

Primary explosives with powerful and reliable stabilities have attractive applications in the field of military and civilian technologies. In this work, four two-dimensional, solvent-free metal azide-based energetic coordination polymers [M(N3)2(btze)]n (M = Co for 1, Cd for 2; btze = 1,2-bis(tetrazol-1-yl)ethane), [Cd2(N3)3Cl(btze)2]n 3, and [Cd2(N3)2Br2(btze)2]n 4 were prepared through a hydrothermal reaction and structurally characterized by single-crystal X-ray diffraction. All four compounds exhibit two times higher heats of detonation than that of the traditional lead azide (LA), high thermal stabilities (>200 °C), and relatively low sensitivities. The values of enthalpies of formation (ΔfH°) of 1 and 2 are high up to 4.088 and 3.925 kJ·g–1, respectively, which belong to those of the largest ΔfH° values among metal-based primary explosives. Although 1 and 2 are isostructural energetic compounds, their mechanical sensitivities are discrepant, which mainly originates from different metal atomic radii ...