| Abstract: | Solvent molecules can significantly reduce the heat of detonation and stability of energetic metal-organic framework (EMOF) materials, and the development of solvent-free EMOFs has become an effective strategy to prepare high-energy density materials. In this study, a solvent-free EMOF, Ag2(DTPZ)]n (1) (N% = 32.58%), was synthesized by reacting a high-energy ligand, 2, 3-di(1H-tetrazol-5-yl)pyrazine (H2DTPZ), with silver ions under hydrothermal conditions, and it was structurally characterized by elemental analysis, infrared spectroscopy, X-ray diffraction, and thermal analysis. In 1, the DTPZ2? ligands that adopted a highly torsional configuration bridged the Ag+ ions in an octadentate coordination mode to form a three-dimensional framework (ρ = 2.812 g?cm?3). The large steric effect and strong coordination ability of DTPZ2? effectively prevented the solvent molecules from binding with the metal centers or occupying the voids of 1. Moreover, the strong π-π stacking interactions centroid-centroid distance = 0.34461(1) nm] between the tetrazole rings in different DTPZ2? ligands provided a high thermal stability to the framework (Te = 619.1 K, Tp = 658.7 K). Thermal analysis showed that a one-step rapid weight loss with intense heat release primarily occurred during the decomposition of 1, suggesting potential energetic characteristics. Non-isothermal thermokinetic analyses (based on the Kissinger and Ozawa-Doyle methods) were performed using differential scanning calorimetry to obtain the thermoanalysis kinetic parameters of the thermodecomposition of 1 (Ea = 272.1 kJ·mol?1, Eo = 268.9 kJ·mol?1; lgA =19.67 s?1). The related thermodynamic parameters enthalpy of activation (ΔH≠ = 266.9 kJ·mol?1), entropy of activation (ΔS≠ = 125.4 J·mol?1·K?1), free energy of activation (ΔG≠ = 188.3 kJ·mol?1)], critical temperature of thermal explosion (Tb = 607.1 K), and self-accelerating decomposition temperature (TSADT = 595.8 K) of the decomposition reaction were also calculated based on the decomposition peak temperature and extrapolated onset temperature when the heating rate approached zero. The results revealed that 1 featured good thermal safety, and its decomposition was a non-spontaneous entropy-driven process. The standard molar enthalpy for the formation of 1 was calculated to be (2165.99 ± 0.81) kJ·mol?1 based on its constant volume combustion energy determined using a precise rotating oxygen bomb calorimeter. Detonation and safety performance tests revealed that 1 was insensitive to impact and friction, and its heat of detonation (10.15 kJ·g?1) was higher than that of common ammonium nitrate explosives, such as octogen (HMX), hexogene (RDX), and 2, 4, 6-trinitrotoluene (TNT), indicating that 1 is a promising high-energy and insensitive material. |
