3D Electron-Rich ZIF-67 Coordination Compounds Based on 2-Methylimidazole: Synthesis, Characterization and Effect on Thermal Decomposition of RDX, HMX, CL-20, DAP-4 and AP

ZIF-67 is a three-dimensional zeolite imidazole ester framework material with a porous rhombic dodecahedral structure, a large specific surface area and excellent thermal stability. In this paper, the catalytic effect of ZIF-67 on five kinds of energetic materials, including RDX, HMX, CL-20, AP and the new heat-resistant energetic compound DAP-4, was investigated. It was found that when the mass fraction of ZIF-67 was 2%, it showed excellent performance in catalyzing the said compounds. Specifically, ZIF-67 reduced the thermal decomposition peak temperatures of RDX, HMX, CL-20 and DAP-4 by 22.3 °C, 18.8 °C, 4.7 °C and 10.5 °C, respectively. In addition, ZIF-67 lowered the low-temperature and high-temperature thermal decomposition peak temperatures of AP by 27.1 °C and 82.3 °C, respectively. Excitingly, after the addition of ZIF-67, the thermal decomposition temperature of the new heat-resistant high explosive DAP-4 declined by approximately 10.5 °C. In addition, the kinetic parameters of the RDX+ZIF-67, HMX+ZIF-67, CL-20+ZIF-67 and DAP-4+ZIF-67 compounds were analyzed. After the addition of the ZIF-67 catalyst, the activation energy of the four energetic materials decreased, especially HMX+ZIF-67, whose activation energy was approximately 190 kJ·mol(−1) lower than that reported previously for HMX. Finally, the catalytic mechanism of ZIF-67 was summarized. ZIF-67 is a potential lead-free, green, insensitive and universal EMOFs-based energetic burning rate catalyst with a bright prospect for application in solid propellants in the future.