Nitrogen-Rich Salts Based on the Energetic [Monoaquabis(N,N-bis(1H-tetrazol-5-yl)amine)-zinc(II)] Anion: A Promising Design in the Development of New Energetic Materials

Lithium-Promoted Formation of (M = N2H5+ or NH3OH+ and = Anion of 1-Hydroxytetrazole-5-hydrazide)-Type "Quaternary" Complexes with Nitrogen-Rich Characteristics: Construction of Novel Insensitive Energetic Materials

Lithium-based nitrogen-rich complexes are important research objects in the field of high-energy materials. However, the weak coordination abilities of lithium ions relative to those of other metal ions with greater atomic numbers have hindered their applications in the field of nitrogen-rich complexes. Herein, we successfully prepared novel lithium-based nitrogen-rich complexes (N₂H₅-2AZTO-Li and NH₃OH-2AZTO-Li) by exploiting the structural properties of 1-hydroxytetrazolium-5-hydrazine (HAZTO). Both N₂H₅-2AZTO-Li and NH₃OH-2AZTO-Li were found to exhibit physicochemical parameters (including the density, stability, and energetic properties) that were intermediate between those of the simple ionic compounds (3 and 4) and the complexes (5) that formed them, enabling a favorable balance between high energy, high stability, and environmental friendliness (for N₂H₅-2AZTO-Li: detonation velocity (D) = 9005 m s^-1, detonation pressure (P) = 35.5 GPa, decomposition temperature (T_dec) = 238.1 °C, impact sensitivity (IS) = 24 J, friction sensitivity (FS) = 210 N, and detonation product (DP) (CO) < 2%; for NH₃OH-2AZTO-Li: D = 9028 m s^-1, P = 35.7 GPa, T_dec = 211.2 °C, IS = 20 J, FS = 180 N, and DP (CO) < 2%). This study transcends the conventional structural forms of nitrogen-rich complexes, opening new horizons for the design of novel insensitive energetic materials.

Modulating energetic performance through decorating nitrogen-rich ligands in high-energy MOFs

In the presence of different nitrogen-rich ligands, two energetic MOFs with formulas [Ag(tza)]_n (1) and [Ag(atza)]_n (2) (Htza = tetrazole-1-acetic acid and Hatza = (5-amino-1H-tetrazole-1-yl) acetic acid) were successfully synthesized and characterized. X-ray single crystal structure analysis shows that both 1 and 2 have 2D layer-like topologies. The experimental and theoretical evaluations reveal the promising properties of both energetic compounds, such as prominent heats of detonation, high thermal stabilities, good sensitivities and excellent detonation performances. In contrast to 1, interestingly, the introduction of the amino group in 2 leads to various coordination modes of the ligands and different stacking patterns of the frameworks, resulting in the observation of the shorter Ag-O, Ag-Ag, C-N, N-N, and N[double bond, length as m-dash]N bond lengths in 2. Consequently, 2 features superior heats of detonation and thermostability compared to 1. The nonisothermal thermokinetic parameters are obtained by using the Kissinger and Ozawa methods, while the standard molar enthalpies of formation are calculated from the determination of constant volume combustion energies. In addition, both compounds were explored as practical additives to promote the thermal decomposition of ammonium perchlorate (AP). This work may provide an effective approach for manipulating the energetic properties and thermostability of high-energy compounds via the perturbation of energetic groups.

Photodegradation of bis(1H-tetrazol-5-yl)amine (H2BTA), a high nitrogen content tetrazole-based energetic compound in water

Tetrazoles have wide industrial applications, notably in the pharmaceutical industry. Tetrazole derivatives such as bis(1H-tetrazol-5-yl)amine (H₂BTA) have recently been considered by the defense industry as high nitrogen composite propellants. Photodegradation studies under solar simulating conditions showed that H₂BTA was partially degraded in water, while it was completely degraded under UV light at 254 nm. When H₂BTA (0.35 mM) was irradiated with simulated sunlight at pH 3.65, there was a 1-day lag phase before the chemical started to degrade, reaching 43.5% degradation after 7 d. However, when pH increased to 5.76, it degraded without lag phase, suggesting that an HBTA^- anion was involved in the initial degradation of the chemical. 5-Aminotetrazole (5-AT) was identified as a final degradation product and N-(1H-tetrazol-5-yl)formamide(T(5 yl)FA) and 1H-tetrazol-5-ylcarbamic acid (T(5 yl)CA) as intermediate products. At λ = 254 nm, H₂BTA disappeared rapidly, resulting in the loss of 94% after 65 min. 5-AT was detected together with several transient products including N-(1H-tetrazol-5-yl)carbamohydrazonic acid (T(5 yl)CHA) and T(5 yl)FA. Kinetic studies and products analysis revealed that H₂BTA photodegraded via two initial routes. One route (a) marked by the initial loss of HN₃ and another (b) marked by the initial loss of N_2. Route a) was characteristics for irradiation with simulated sunlight; however, routes a) and b) proceeded simultaneously under UV light. 5-AT eventually degraded to presumably give N₂ and/or HN₃ under UV light. Understanding the photodegradation pathway of H₂BTA under simulated sunlight can help in providing the basis for natural attenuation assessment of the chemical in contaminated aquatic environments.

Modification of crystalline energetic salts through polymorphic transition: enhanced crystal density and energy performance

We presented a detailed investigation of polymorphic transition of energetic salts and explored a new path for modifying crystalline energetic salts.

Molecular dynamics simulations of a cyclotetramethylene tetra-nitramine/hydrazine 5,5'-bitetrazole-1,1'-diolate cocrystal

An energetic ionic salt (EIS)-based cocrystal formation, cyclotetramethylene tetra-nitramine (HMX)/hydrazine 5,5′-bitetrazole-1,1′-diolate (HA·BTO), is predicted based on molecular dynamics simulations. HA·BTO is a newly-synthesized environmentally friendly energetic ionic salt with good detonation performance and low sensitivity. Calculated powder X-ray diffraction patterns and intermolecular interactions deduce the formation of the new cocrystal structure. Radial distribution function analysis suggests that hydrogen bonds and van der Waals (vdW) forces exist between the H⋯O pairs of HMX and HA·BTO, while the hydrogen bonds between the H of HA·BTO and the O of HMX play a prominent role. The cohesive energy density and mechanical properties are also analyzed. The cohesive energy density of the HMX/HA·BTO cocrystal is larger than that of the composite of HMX and HA·BTO, indicating an improvement in crystal stability by cocrystalization. Compared to both HMX and HA·BTO, HMX/HA·BTO has smaller Young modulus, bulk modulus and shear modulus values, but larger K/G values and a positive Cauchy pressure, suggesting decreased stiffness and improved ductibility. Moreover, the calculated formation energy is −405.79 kJ mol⁻¹ at 298 K, which implies that the proposed cocrystal structure is likely to be synthesized at ambient temperature. In summary, we have predicted an EIS-based cocrystal formation in which the safety and mechanical properties of HMX have been improved via cocrystalization with HA·BTO, and this provides deep insight into the formation mechanism of the EIS-based cocrystal.

An energetic ionic salt-based cocrystal formation, HMX/HA·BTO, is predicted based on molecular dynamics simulations.

Crystal structures, thermodynamics and accelerating thermal decomposition of RDX: two new energetic coordination polymers based on a Y-shaped ligand of tris(5-aminotetrazole)triazine

Two new energetic coordination polymers were prepared under hydrothermal condition. They have good detonation velocity, detonation pressure and effective acceleration effect toward the thermal decomposition of RDX (1,3,5-trinitro-1,3,5-triazinane).

A highly stable and tightly packed 3D energetic coordination polymer assembled from nitrogen-rich tetrazole derivatives

A tightly packed 3D energetic cadmium(ii) coordination polymer was synthesized with high stability and remarkable energetic performance.

Bottom-up design of high-energy-density molecules (N2CO)n (n = 2–8)

A bottom-up strategy from an HEDM seed (i.e., cyc-N₂CO) to novel oligomeric HEDMs was propsed.

Three new energetic complexes with N,N-bis(1H-tetrazole-5-yl)-amine as high energy density materials: syntheses, structures, characterization and effects on the thermal decomposition of RDX

Three new complexes can be used as HEDMs. Insensitive 2 is a safer form for storage and transportation than sensitive 3.

Nitrogen-Rich Energetic Metal-Organic Framework: Synthesis, Structure, Properties, and Thermal Behaviors of Pb(II) Complex Based on N,N-Bis(1H-tetrazole-5-yl)-Amine

The focus of energetic materials is on searching for a high-energy, high-density, insensitive material. Previous investigations have shown that 3D energetic metal-organic frameworks (E-MOFs) have great potential and advantages in this field. A nitrogen-rich E-MOF, Pb(bta)·2H₂O [N% = 31.98%, H₂bta = N,N-Bis(1H-tetrazole-5-yl)-amine], was prepared through a one-step hydrothermal reaction in this study. Its crystal structure was determined through single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, and elemental analysis. The complex has high heat denotation (16.142 kJ·cm^-3), high density (3.250 g·cm^-3), and good thermostability (T_dec = 614.9 K, 5 K·min^-1). The detonation pressure and velocity obtained through theoretical calculations were 43.47 GPa and 8.963 km·s^-1, respectively. The sensitivity test showed that the complex is an impact-insensitive material (IS > 40 J). The thermal decomposition process and kinetic parameters of the complex were also investigated through thermogravimetry and differential scanning calorimetry. Non-isothermal kinetic parameters were calculated through the methods of Kissinger and Ozawa-Doyle. Results highlighted the nitrogen-rich MOF as a potential energetic material.

Hydrazine 5,5′-bitetrazole-1,1′-diolate: a promising high density energetic salt with good properties

The salt HA·BTO has proved to be a good insensitive explosive alternative, and has promising application as an RDX replacement.

Synthesis, crystal structure and properties of a new 1D polymeric nitrogen-rich energetic complex {TAG[Li(BTO)(H2O)]}n based on 1H,1′H-5,5′-bitetrazole-1,1′-diolate

The novel polymer {TAG[Li(BTO)(H₂O)]}_n, based on 1H,1′H-5,5′-bitetrazole-1,1′-diolate, opened up a new field on BTO-based energetic materials and anionic metal–organic frameworks.

3D Nitrogen-rich metal–organic frameworks: opportunities for safer energetics

3D Nitrogen-rich MOFs as newly emerged energetic materials have experienced rapid development in the last few years. This Frontier Article highlights the most up-to-date progress in this field.

A novel insensitive cocrystal explosive BTO/ATZ: preparation and performance

A new insensitive co-crystal explosive, BTO/ATZ, has a promising future for use as an insensitive explosive.

High performance 5-aminotetrazole-based energetic MOF and its catalytic effect on decomposition of RDX

The energetic compound [Ag₂(5-ATZ)(N₃)] (1) features a compacted 3D framework structure, remarkable thermostability above 300 °C and perfect detonation performance. Remarkably, 1 can accelerate effectively the thermal decomposition of RDX.