Investigation of CL-20/TFAZ cocrystal: preparation, structure and performance

Abstract

The cocrystals of hexanitrohexaazaisowurtzitane (CL-20) and 7H-trifurazano[3,4-b:3’,4’-f:3”,4”-d]azepine (TFAZ) in a 1 : 1 molar ratio were prepared by both slow evaporation and self-assembly method. Structure determination showed that it belongs to the monoclinic system (space group P21) with crystal density of 1.932 g cm−3. The intermolecular hydrogen bonds and N–O•••NO2 type interactions are demonstrated as the predominant driving force in cocrystal formation. Furthermore, the cocrystals were successfully synthesized by a self-assembly method using only water as solvent at mild conditions, and the product yield was up to 92.3%. The two types of cocrystals were fully characterized by powder X-ray diffraction and scanning electron microscope. Moreover, the thermal behavior, sensitivity, and calculated detonation performances of the cocrystal were evaluated. The cocrystal exhibits good thermal stability (Td = 242.8 °C), low impact sensitivity (H50 = 42 cm) and friction sensitivity (Pf = 38%), high crystal density, and high calculated detonation velocity (9103 m/s). This work opens up a new perspective in the environment-friendly preparation of energetic cocrystals on a large-scale, as well as provides a potential low-sensitivity and high-energy explosive.