The design and synthesis of novel energetic compounds with integrated properties of high density, high energy, good thermal stability and sensitivities is particularly challenging due to the inherent contradiction between energy and safety for energetic compounds. In this study, a novel structure of 4-amino-7,8-dinitropyrazolo-[5,1-d] [1,2,3,5]-tetrazine 2-oxide (BITE-101) is designed and synthesized in three steps. With the help of the complementary advantages of different explosophoric groups and diverse weak interactions, BITE-101 is superior to the benchmark explosive HMX in all respects, including higher density of 1.957 g·cm−3, highest decomposition temperature of 295 °C (onset) among CHON-based high explosives to date and superior detonation velocity and pressure (D: 9314 m·s−1, P: 39.3 GPa), impact and friction sensitivities (IS: 18 J, FS: 128 N), thereby showing great potential for practical application as replacement for HMX, the most powerful military explosive in current use.

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Understanding the structure–property relationship in a material is of great importance in materials science. To study the effect of ligand backbones and anionic groups on the properties of energetic cationic metal–organic frameworks (CMOFs) and to disclose their structure–property relationships, we designed and synthesized a series of CMOFs based on either 4,4′-bi-1,2,4-triazole (btrz) or its azo analogous, 4,4′-azo-1,2,4-triazole (atrz) as ligand, and either perchlorate [ClO4 –] or nitroformate [C­(NO2)3 –, NF–] anion as extra-framework anion. Surprisingly, the effect of ligand backbones on the CMOFs is inverse that of the backbones on traditional energetic compounds, while the effect of the anionic groups follows the traditional group law. We found that btrz-based CMOFs exhibit higher densities and better chemical and thermal stabilities than those of their corresponding atrz-based CMOFs, although btrz has a lower density and a lower stability than atrz. In particular, the density of btrz-Fe is more than 0.11 g cm–3 higher than that of its atrz-based analogue (atrz-Fe). Moreover, the decomposition temperature of btrz-Zn (363 °C) is 80 °C higher than that of atrz-Zn, even higher than that of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), making it a potential heat-resistant explosive. The effect mechanisms were also discussed according to the experimental results. This investigation is significant for understanding the structure–property relationship in energetic CMOFs. Moreover, it also brings about new design rules for future high-performance energetic materials.

Cocrystallization of energetic compounds has recently been considered as an effective method to adjust the properties through the selection of coformers, particularly to improve the detonation properties and reduce the mechanical sensitivity of CL-20. In this research, a reliable and promising design strategy to synthesize CL-20-based cocrystals was presented, where (i) the coformer should show local structural similarity to CL-20, i.e., fiveor sixmembered symmetric heterocycles, and (ii) the molecular structure of the coformer should contain electron-donating groups. In order to verify the adaptability of this design strategy, pyrazine, 2,6-dimethoxy-3,5-dinitropyrazine, and 2,5-dimethylpyrazine were selected as the templates of six-membered symmetrical N-heterocyclic compounds for cocrystallization with CL-20. Fortunately, on the basis of the results of the experiments and the crystal analysis, three compounds were successfully cocrystallized with CL-20. Moreover, two cocrystals with the same components and different stoichiometric ratios were formed by pyrazine and CL-20. In addition, the properties of the designed cocrystals, including thermal stability, detonation properties, and sensitivities, were also studied in detail. Cocrystallization of CL-20 with the aforementioned coformers demonstrates the appropriateness of six-membered symmetrical N-heterocyclic compounds as coformers. In light of this finding, the safety and detonation properties of CL-20 can be modulated by employing suitable six-membered N-heterocyclic compounds as coformers.

The investigation of high-nitrogen compounds has been significant for the evolution of energetic materials. Azo-bis-1,2,4-triazole (aTRz) can be an excellent energetic backbone, owing to its characteristics: high heat of formation, high nitrogen content, and plane structure. Nevertheless, aTRz-based energetic compounds have been rarely synthesized using the covalent modification method, owning to the decomposition of aTRz under harsh reaction conditions. Cocrystallization has been widely used as a mild and efficient method for modulating the properties of energetic compounds. In this study, electrostatic potential (ESP) maps were used for theoretical guidance, and four aTRz-based energetic cocrystals have been obtained via cocrystallization. The single-crystal structures of these cocrystals indicated that the N···H–N hydrogen bonds between the side nitrogen atoms of aTRz and the amino groups of the nitro azole compounds were the driving force for the assembly of multimers with aTRz and polynitroazole compounds. Consequently, the formation of cocrystals via the self-assembly of these multimers was driven by other weak hydrogen bonds and van der Waals forces. The detonation performance of aTRz-based cocrystals was increased by appropriately selecting the coformers. Particularly, when 4-amino-3,5-dinitro-pyrazole (ADNP) was used as coformer, resultant cocrystal 3 was a potential high-energy density material that exhibited high density, high detonation velocity (8329 m s–1) and detonation pressure (28.6 GPa). Thus, in this study, cocrystallization has been demonstrated to be an effective method for the noncovalent modification of aTRz-based energetic materials.