Acta Physico-Chimica Sinica ›› 2020, Vol. 36 ›› Issue (6): 1905085.doi: 10.3866/PKU.WHXB201905085

Special Issue: Thermal Analysis Kinetics and Thermokinetics

• Article • Previous Articles     Next Articles

Synthesis, Thermal Decomposition Kinetics and Detonation Performance of a Three-Dimensional Solvent-Free Energetic Ag(I)-MOF

Chengfang Qiao1,Lei Lü3,Wenfeng Xu2,Zhengqiang Xia2,Chunsheng Zhou1,Sanping Chen2,*(),Shengli Gao1,2   

  1. 1 Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources, College of Chemical Engineering and Modern Materials, Shangluo University, Shangluo 726000, Shaanxi Province, P. R. China
    2 Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi'an 710127, P. R. China
    3 Department of Chemistry and Chemical Engineering, Shaanxi Key Laboratory of Chemical Reaction Engineering, Yan'an University, Yan'an 716000, Shaanxi Province, P. R. China
  • Received:2019-05-31 Accepted:2019-06-27 Published:2019-12-18
  • Contact: Sanping Chen E-mail:sanpingchen@126.com
  • Supported by:
    the National Natural Science Foundation of China(21727805);the National Natural Science Foundation of China(21673180);the National Natural Science Foundation of China(21703135);the National Natural Science Foundation of China(21803042);Natural Science Basic Research Program of Shaanxi(2017JZ002);Natural Science Basic Research Program of Shaanxi(2018JM5180);Natural Science Basic Research Program of Shaanxi(2019JQ-249);Natural Science Basic Research Program of Shaanxi(2019JQ-067);the Project of Shaanxi Key Laboratory of Chemical Reaction Engineering(14JS112);the 64th China Postdoctoral Science Foundation Funded Project(2018M643706)

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.

Key words: Energetic metal-organic framework, Thermal decomposition kinetics, Thermal stability, Detonation performance, Sensitivity

MSC2000: 

  • O642