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Oxidation of nitrogen-rich aromatic heterocycles has a significant impact on the development of energetic materials. 2,4,6-Triamino-1,3,5-triazine-1,3-dioxide (MDO) is a promising insensitive energetic backbone obtained from melamine under strong oxidation conditions with impressive thermal behaviors and detonation performances. In this paper, MDO was prepared with improved yields of 85% and its thermal behavior, non-isothermal decomposition kinetics and gas products were investigated in detail. The corresponding decomposition mechanism was also deduced by applying the TG-DSC-FTIR-MS technique for the first time. The decomposition temperature of MDO reaches 300 °C and the apparent activation energy of MDO (E) calculated by the Kissinger and Ozawa method proved to be 303.63 and 279.95 kJ mol−1, indicating great thermal stability. Three new monoanionic energetic salts with impressively improved properties were achieved based on the basicity of MDO with yields of >80%. Their thermal decomposition temperatures proved to be higher than 230 °C and their densities are in the range of 1.75–1.89 g cm−3. The calculations and experiments show that their detonation velocities (vD: 8711–9085 m s−1) are comparable to or exceed those of RDX (D: 8795 m s−1) while the sensitivities to impact (IS: 23–27 J) and friction (FS: >240 J) are much lower.

Although energetic regioisomers have attracted intensive attention due to their interesting structure–property correlation, their effective synthesis and accurate identification has remained very difficult. In this paper, we synthesized two energetic regioisomers, namely 3-(4-aminofurazan-3-yl)-4-(4-nitrofurazan-3-yl)furoxan (ANFF-34) and 4-(4-aminofurazan-3-yl)-3-(4-nitrofurazan-3-yl)furoxan (ANFF-43), via a controllable strategy with improved yields of 32% and 38%, respectively. The structures of ANFF-34 and ANFF-43 were unambiguously identified using comparative studies of 15N NMR and single-crystal X-ray diffraction. Moreover, their thermal behaviours, and non-isothermal thermodynamic parameters were systematically investigated. Both ANFF-34 (Tm: 116.2 °C, Td: 255.4 °C) and ANFF-43 (Tm: 106.2 °C, Td: 255.6 °C) have similar thermal decomposition processes to that of DNTF. The superior performances of ANFF-34 (ρ: 1.8 g cm−3, D: 8214 m s−1, P: 30.5 GPa, IS > 40 J) and ANFF-43 (ρ: 1.7 g cm−3, D: 7868 m s−1, P: 27.0 GPa, IS > 40 J) indicate their great potential to be used as melt-cast carrier explosives. This study provides a solid foundation for the design and synthesis of new energetic compounds through isomer effects.

The introduction of fluorodinitromethyl energetic groups is an efficient strategy to improve the performances of energetic materials. In this paper, an insensitive energetic compound 6-(fluorodinitromethyl)-3-nitro-1,2,3,4-tetrahydro-1,3,5-triazine (FMTNT) was designed and synthesized based on the modification of 1,3,5-triazine backbone via the nitration-rearrangement, reduction and fluorination sequence. The single crystal of FMTNT was firstly obtained and determined, meanwhile, this novel structure was also fully characterized by the methods of IR, 1H NMR, 13C NMR, 19F NMR and elemental analysis. Studies on thermal behaviors and detonation performances of FMTNT were also carried out through differential scanning calorimetry (DSC-TG) approach and EXPLO5 program, respectively. The decomposition temperature of FMTNT is found to be at 157.5 °C via thermal chemical analysis and the detonation performances were proved to be good, with a detonation velocity of 8624.8 m s−1 and detonation pressure of 29.1 Gpa. Furthermore, the experimental results showed that impact and friction sensitivity reaches 20 J and 240 N, even less sensitive than TNT, indicating a broad perspective in the application of insensitive explosives and propellants.

Density, detonation property, and sensitivity may be the most valued features when evaluating an energetic material. By reasoning structure–property relationships, a nitro-free planar energetic material with high nitrogen and oxygen content, 7-hydroxy-difurazano[3,4-b:3’,4’-f]furoxano[3’’,4’’-d]azepine (4), was synthesized using a unique and facile approach. The structure was fully characterized by IR and NMR spectra, elemental analysis, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. The expected properties of 4, including a high density of 1.92 g cm−3, high detonation velocity of 8875 m s−1, and low mechanical sensitivities (impact sensitivity, 21 J and friction sensitivity, >360 N), confirm our strategy. Interestingly, the single-crystal structures of 4 reveal expected face-to-face and unprecedented edge-to-face π-interactions in the crystal stacking. The remarkable differences in crystal stacking of 4 provide unequivocal evidence that face-to-face π-π interactions contribute significantly to closer assembly and higher density.

Maximization of the energy capability of energetic materials by organizing energetic moieties into dense arrangements is of great significance. In this study, two novel high-energy regioisomers, 3,4–bis(3–fluorodinitromethylfuroxan-4-yl) furoxan (BFTF-1) and 3,4–bis(4–fluorodinitromethylfuroxan-3-yl) furoxan (BFTF-2), were synthesized by employing controllable synthetic strategy. The constitutional isomers were thoroughly characterized using multinuclear NMR and IR spectroscopy, elemental analysis as well as single-crystal X-ray diffraction. Notably, BFTF-1 shows the highest crystal density (ρ: 2.00 g cm−3, 296 K) among fluorodinitromethyl-functionalized CHNOF compounds reported thus far and outstanding detonation performances (D: 9509 m s−1, P: 42.6 GPa), which are significantly higher than that of BFTF-2 (ρ: 1.91 g cm−3, D: 9196 m s−1). The remarkable differences in inter- and intra-molecular interactions of BFTF-1 and BFTF-2 provide unequivocal evidence that the synergistic actions between fluorodinitromethyl and furoxan play a key role in crystal stacking, eventually causing a significant difference in density. This research demonstrates that regiochemical modulation via reasonable design could be a powerful tool to enhance the density and detonation property in the development of new energetic materials.

A new green primary explosive, dipotassium 3,4-bis(3-dinitromethylfurazan-4-oxy)furazan (K2BDFOF), was synthesized via a four-step procedure including cyano addition, diazotization, N2O5 nitration, and KI reduction. The compound was characterized by multinuclear NMR spectroscopy, IR spectroscopy, elemental analysis, DSC, TG/DTG as well as single crystal X-ray diffraction. X-ray diffraction studies reveal an intriguing 3D framework structure. The central K ions are linked by dinitromethanide anions to give a 1D spiral chain with parallelogram-like repeat units, and these 1D chains are further linked by one oxygen atom in the nitro group coordinated with a K ion to form a two-dimensional wave-like layer structure. Additionally the kinetic parameters of the exothermic process for K2BDFOF were studied by Kissinger's and Ozawa–Doyle's methods. The sensitivities were determined by standardised impact and friction tests, and the heat of formation was calculated with the atomization method at the CBS-4M level of theory. With the heat of formation (−8.4 kJ mol−1) and the room-temperature X-ray density (2.09 g cm−3), impressive values for the detonation parameters such as detonation velocity (8431 m s−1) and pressure (329 kbar) were computed using the EXPLO5 program and compared to the most commonly used primary explosive, lead azide, as well as the recently published dipotassium 1,1′-dinitramino-5,5′-bistetrazolate.