An energetic ionic salt synthesized based on 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation and a preparation method thereof

Abstract

This invention proposes a two-dimensional layered energetic ionic salt based on 3,5-dinitro-1,2,4-triazole anions and nitrogen-containing cations, and its preparation method. Through a rational design strategy that precisely controls high oxygen balance, high nitrogen content, and a two-dimensional planar structure, the planar configuration of 3,5-dinitro-1,2,4-triazole serves as the anionic framework. This is achieved by targeting and synthesizing a graphite-like layered energetic ionic salt with nitrogen-rich cations in a solvent via hydrogen bonding and ion assembly. This type of two-dimensional layered energetic ionic salt exhibits a stable planar network formed within its layers by numerous strong O···H and N···H hydrogen bonds. The interlayer structure, relying on large interlayer spacing and weak intermolecular forces, forms a slip-like graphite-like stacking structure. This structure can efficiently dissipate external mechanical energy through interlayer slip, significantly reducing the probability of hotspot formation and endowing the compound with excellent low-sensitivity properties. Simultaneously, the compound, with its high nitrogen content, high oxygen balance, and two-dimensional conjugated structure, possesses both ideal thermal stability and excellent detonation performance.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials technology, specifically relating to an energetic ionic salt with a graphite-like layered stacking structure formed by the combination of 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation, and its preparation method. The energetic ionic salt is particularly suitable for preparing insensitive explosives with high safety and high energy density. Background Technology

[0002] Energetic materials are the core energy carriers of modern weaponry, and the synergistic balance between high energy density and low sensitivity has long been a core bottleneck in their molecular design and synthesis. While traditional nitramine explosives (such as RDX, HMX, and CL-20) possess excellent detonation energy levels, their high mechanical sensitivity poses significant safety risks during production, storage, transportation, and service. On the other hand, traditional insensitive explosives, represented by TATB, while offering excellent safety, suffer from shortcomings such as low energy density, high synthesis costs, and insufficient detonation performance, failing to meet the core requirement of advanced weaponry for energetic materials to possess both high energy density and low sensitivity.

[0003] Chinese patent application CN103483264A discloses 1-nitramine-2,4-dinitroimidazole energetic ionic salts. Although this system is synthesized using water as a solvent and has excellent environmental friendliness, its impact sensitivity ranges from 4 to 40 J, with some salts exhibiting relatively high mechanical sensitivity. Furthermore, it lacks a layered hydrogen bond assembly structure, failing to achieve a synergistic balance between energy and safety. Its detonation velocity is 8370–9209 m / s, comparable only to RDX, failing to achieve a simultaneous breakthrough in high energy and low sensitivity. Chinese patent CN109053614B discloses triazine cationic nitrogen-rich energetic ionic salts with detonation velocities reaching 8534–9259 m / s and impact sensitivity >20 J. However, this system does not form a graphite-like layered structure with strong intralayer hydrogen bonds and interlayer π-π stacking, resulting in a less than expected synergistic improvement in thermal stability and energy density. The trinitramine triazolotriazole energetic ionic salt disclosed in Chinese patent CN110386938B has a detonation velocity of up to 9518 m / s for some products, but its impact sensitivity is only 4~8 J, resulting in extremely poor mechanical safety. Furthermore, it lacks a layered structure to dissipate impact energy, posing serious safety hazards in practical applications.

[0004] Energetic ionic salts, with their advantages of strong designability of cations and anions, adjustable range of enthalpy of formation, excellent thermal stability, and environmentally friendly decomposition products, have become a core research direction for solving the dilemma of energy versus safety in energetic materials. Among these, the structural design of nitrogen-rich heterocyclic anions is a key factor determining the detonation energy, sensitivity characteristics, oxygen balance, and crystal stacking behavior of ionic salts. 3,5-Dinitro-1,2,4-triazole (DNT), as a typical nitrogen-rich heterocyclic skeleton of nitrotriazoles, possesses extremely outstanding application potential: its nitrogen content is as high as 44.03%, and the abundant N-N and CN high-energy bonds within the molecule endow it with a high positive enthalpy of formation; the dinitro substitution gives it an excellent oxygen balance close to zero, with a theoretical detonation velocity reaching [value missing]. The detonation pressure reaches 30.56 GPa, exhibiting excellent detonation performance. Simultaneously, its strictly planar conjugated structure provides an ideal structural basis for hydrogen bond assembly and π-π stacking, and possesses excellent salt-forming reactivity. However, current technologies only report metal salt derivatives of DNT. While these derivatives reduce sensitivity and improve thermal stability to some extent, they suffer from three major drawbacks: first, the introduction of metal ions significantly reduces the nitrogen content and energy density of the system; second, the coordination and stacking mode of metal ions makes it difficult to form a graphite-like layered slip structure; and third, existing synthesis methods cannot achieve precise control of the layered structure, ultimately leading to disordered crystal stacking and high sensitivity, failing to achieve a balance between energy and safety.

[0005] Therefore, this invention selects 3,5-dinitro-1,2,4-triazole as the anionic ligand and uses guanidinium and ammonium cations to form hydrogen bonds with it to directionally prepare energetic ionic salts with graphite-like layered structures. The aim is to break through the common technical bottleneck in the industry where the energy and safety of existing energetic materials are mutually constrained, and to develop a new type of energetic material with high energy density, low mechanical sensitivity, low thermal sensitivity and environmental friendliness. Summary of the Invention

[0006] (a) Technical problems to be solved This invention provides an energetic ionic salt with a graphite-like layered structure constructed from 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation, and its preparation method. It aims to solve the core technical problem of the difficulty in achieving a synergistic balance between energy density and safety in existing energetic materials, and overcome the defects of traditional ionic energetic compounds, such as disordered crystal stacking, poor controllability of layered structure, high mechanical sensitivity, and complex synthesis processes, low yield, and difficulty in engineering scale-up of some energetic salts.

[0007] (II) Technical Solution To address the aforementioned technical problems, this invention proposes an energetic ionic salt synthesized from 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation. This energetic ionic salt has a graphite-like layered structure, formed by the planar configuration of 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation through hydrogen bonding and π-π stacking interactions to form a two-dimensional mesh-like layered stack.

[0008] Furthermore, the crystal density of the energetic ion salt is 1.623~1.634 g / cm³. 3 Its thermal decomposition temperature is 210~255℃, impact sensitivity is >40J, friction sensitivity is >360N, and detonation velocity is 8152~8655m / s.

[0009] Furthermore, the general formula for energetic ionic salts is [Cation]. m [Anion] n ; where m and n are determined based on the number of Lewis acidic sites and Lewis basic sites, respectively, and take values ​​of 1 or 2.

[0010] Furthermore, nitrogen-containing cations include guanidinium ions and ammonium cations; The molecular formula of the guanidinium ion is:

[0011] The chemical formula of the energetic ion salt is C3H6N8O4; The molecular formula of the ammonium cation is:

[0012] The chemical formula of the energetic ionic salt is C2H8N6O6.

[0013] Furthermore, the energetic ionic salt C3H6N8O4 belongs to the monoclinic crystal system, space group C2 / c, and has a density of 1.661 g / cm³. 3 Energetic ionic salt C2H8N6O6, triclinic crystal system, space group P-1, density 1.623 g / cm³ 3 .

[0014] Furthermore, this invention also proposes a method for preparing the above-mentioned energetic ionic salt based on the synthesis of 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation, which is prepared by solvent heating method and solvent diffusion method based on 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation.

[0015] Furthermore, by adjusting the pH value to 6-7 and the temperature to 60-80℃, the crystallization of energetic ion salts can be achieved.

[0016] Furthermore, the solvent is selected from methanol, ethanol, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, acetone, ethyl acetate and water.

[0017] Furthermore, the sources of guanidinium ions and ammonium cations are guanidine carbonate, guanidine bicarbonate, guanidine hydrochloride, guanidine sulfate, guanidine oxalate, ammonia, ammonium chloride, ammonium oxalate, and ammonium sulfate.

[0018] Furthermore, this invention also proposes an application of the above-mentioned energetic ionic salt synthesized based on 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation, applying the energetic ionic salt to propellants, explosives or insensitive pyrotechnics.

[0019] (III) Beneficial Effects This invention proposes a two-dimensional layered energetic ionic salt based on 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cations such as guanidinium and ammonium, and its preparation method. Through a rational design strategy that precisely controls high oxygen balance, high nitrogen content, and a two-dimensional planar structure, the planar configuration of 3,5-dinitro-1,2,4-triazole serves as the anionic backbone. It is synthesized in a solvent with nitrogen-rich cations such as guanidinium and ammonium via hydrogen bonding and ion assembly, resulting in a graphite-like layered energetic ionic salt. This type of two-dimensional layered energetic ionic salt exhibits a stable planar network formed within the layers by numerous strong O···H and N···H hydrogen bonds. The interlayer structure, relying on large interlayer spacing and weak intermolecular forces, forms a slip-like graphite-like stacking structure, which can efficiently dissipate external mechanical energy through interlayer slip and significantly reduce the probability of hotspot formation, endowing the compound with excellent low-sensitivity properties. Simultaneously, the compound, with its high nitrogen content, high oxygen balance, and two-dimensional conjugated structure, possesses both ideal thermal stability and excellent detonation performance.

[0020] The design and synthesis strategy of this invention can effectively solve the industry problem of the difficulty in balancing the energy and safety of energetic materials, and successfully prepare a new type of energetic element with both high energy density and ultra-low mechanical sensitivity, which can fully meet the core development requirements of modern advanced weapon systems for high energy and high safety of energetic materials. Attached Figure Description

[0021] Figure 1 This is the X-ray single-crystal diffraction pattern of the energetic ionic salt in Example 1; Figure 2 The following are the stacking structure diagrams of the energetic ion salt crystals of Example 1: a) is the molecular structure, b) is the monolayer planar stacking diagram, and c) is the layered stacking diagram. Figure 3 This is the X-ray single-crystal diffraction pattern of the energetic ionic salt in Example 2; Figure 4 The following are the stacking structure diagrams of the energetic ion salt crystals in Example 2: a) is the molecular structure, b) is the monolayer planar stacking diagram, and c) is the layered stacking diagram. Figure 5 The following are the crystal packing diagrams of energetic ionic salts in Examples 1 and 2: a) Crystal packing diagram of ionic salt 1, b) Crystal packing diagram of ionic salt 2; Figure 6 The above are DSC comparison charts of energetic ion salts from Examples 1 and 2. Detailed Implementation

[0022] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0023] Example 1 This embodiment describes the preparation method of the energetic ionic salt C3H6N8O4 (ionic salt 1), and its reaction route is shown below:

[0024] Weigh 0.1 mmol (15.9 mg) of 3,5-nitro-1,2,4-triazole and 0.1 mmol of guanidinium ion, and dissolve them in 3 ml of distilled water. Stir the reaction mixture at 65 °C for 2 hours, allow it to cool naturally to room temperature, and obtain yellow transparent crystals by solvent evaporation.

[0025] The ionic salt 1 obtained in this embodiment was characterized by X-ray single-crystal diffraction. The X-ray single-crystal diffraction pattern is shown below. Figure 1 As shown, the crystallographic parameters are shown in Table 1.

[0026] Table 1 Crystallographic parameters of ionic salt 1

[0027] The results show that ionic salt 1 belongs to the monoclinic crystal system, space group C2 / c, and has the following cell parameters: a=8.488 (2) Å, b=16.845 (4) Å, c=12.430 (3) Å, α=90°, β=100.987 (4)°, γ=90°, Z=8, and the crystal density is 1.661 g·cm³. -3 Each ionic salt unit consists of a guanidinium cation and a 3,5-nitro-1,2,4-triazole anion, which assemble into a planar network structure through intermolecular O…H and N…H hydrogen bonds between adjacent anions and cations. Its crystal packing structure was analyzed using the Cambridge Structure Database (CSD) software Mercury, and its crystal packing structure diagram is shown below. Figure 2As shown, a) is the molecular structure, b) is the monolayer planar packing diagram, and c) is the layered packing diagram. The bond angles in the molecular skeleton range from 103.83 to 116.7°, exhibiting a regular configuration. The dihedral angles are all between -171.8° and 180.0°, and the unit cell arrangement of ionic salt 1 is extremely close to a planar arrangement. The D…A bond lengths of N7-H7A…O3, N6-H6A…N3, and N8-H8B…N2 are between 2.09 and 2.24 Å, which are relatively short and indicate relatively strong interactions.

[0028] Example 2 This embodiment describes a method for preparing the energetic ionic salt C2H8N6O6 (ionic salt 2), and the reaction route is shown below:

[0029] 3,5-nitro-1,2,4-triazole (0.1 mmol, 15.9 mg) and ammonium ions (0.1 mmol) were dissolved in 3 ml of distilled water. After complete dissolution, the mixture was reacted at 65 °C for 2 h, then allowed to cool naturally to room temperature, and volatilized in air to give yellow transparent crystals.

[0030] The ionic salt 2 obtained in this embodiment was characterized by X-ray single-crystal diffraction. The X-ray single-crystal diffraction pattern is shown below. Figure 3 As shown, the crystallographic parameters are shown in Table 2.

[0031] Table 2 Crystallographic parameters of ionic salt 2

[0032] The results showed that ionic salt 2 belongs to the triclinic crystal system with space group P-1 and also exhibits a unique 2D planar structure. Each ionic salt 2 unit consists of an ammonium cation, a 3,5-dinitro-1,2,4-triazole anion, and two water molecules. Its planar network structure is constructed through O…H and N…H hydrogen bonds between adjacent anions and cations. Its cell parameters are as follows: a=4.6565 (11) Å, b=6.4670 (16) Å, c=7.6317 (19) Å, α=93.184 (10)°, β=93.942 (9)°, γ=108.236 (9)°, Z=1, and the crystal density is 1.623 g·cm³. -3 Its crystal packing structure was analyzed using Mercury chromatography, and its crystal packing structure diagram is shown below. Figure 4As shown, a) is the molecular structure, b) is the monolayer planar packing diagram, and c) is the layered packing diagram. The interior angles in the monocyclic molecular skeleton are between 104.66 and 117.24°, close to the 108° interior angle of a regular pentagon. The dihedral angles are all between 175.8 and 180.0°, and the unit cell arrangement of ionic salt 2 is extremely close to planar arrangement. The bond lengths of O7-H7B...O5, N6-H6A...O7, O5-H5B...N3, N6-H6B...O5, and O7-H7A...N4 are between 1.97 and 2.03 Å, which are relatively short and strong.

[0033] The crystal structures and key bond length parameters of ionic salt 1 and ionic salt 2 are as follows: Figure 5 As shown; its thermal properties were characterized by differential scanning calorimetry (DSC) (test curves are shown in Figure 1). Figure 6 As shown in Table 3, key performance parameters such as detonation were calculated using ExploML and EXPLO5 software. Specific data are detailed in Table 3.

[0034] Table 3 Performance of the energetic ionic salts, TNT, and RDX obtained in Examples 1 and 2

[0035] [a] Initial decomposition temperature determined by differential scanning calorimetry (DSC) at a heating rate of 10°C / min; [b] Density measured by a gas hydrometer at 25°C; [c] Oxygen content; [d] Nitrogen content; [e] Impact sensitivity assessed using the 2.5kg BAM technique; [f] Friction sensitivity assessed using the BAM technique.

[0036] Comparing the performance of energetic ionic salts with TNT and RDX in Table 3, we can see that: 1. The detonation velocity and detonation pressure of the energetic ion salt prepared by this invention are much higher than those of TNT, exhibiting high detonation performance; 2. The energetic ion salt prepared by this invention has a high nitrogen content, and its impact and friction sensitivity are much higher than those of TNT and RDX, thus ensuring safety during production, transportation and use. 3. The synthetic route of this invention is simple, and the purification method is simple and easy to implement, making it suitable for industrial production.

[0037] This invention employs a rational design strategy that precisely controls high oxygen balance and high nitrogen content while constructing a two-dimensional planar structure. Using a planar configuration of 3,5-dinitro-1,2,4-triazole as the anionic framework, combined with nitrogen-rich cations such as guanidinium and ammonium, stable O···H and N···H hydrogen bonds and ionic bonds are formed between molecules through ionic assembly in aqueous solution at room temperature and simple acid-base reactions. This directionally prepares novel low-sensitivity energetic ionic salts with a two-dimensional layered stacking structure, significantly improving the targeted synthesis efficiency of layered energetic ionic salts. At the same time, it enriches the structural types of high-energy, low-sensitivity energetic ionic salts, providing core technical support for achieving a synergistic balance between high energy and low sensitivity in the field of energetic materials.

[0038] The two-dimensional layered structure of energetic ionic salts endows compounds with superior thermal stability and safety in use. A dense planar network structure is formed within the layers through numerous strong hydrogen and ionic bonds, providing a larger molecular contact area during crystal stacking. This ensures both energy transfer efficiency and detonation reaction performance while enhancing structural stability. The large spacing between layers allows for rapid diffusion and dissipation of energy generated by external mechanical stimuli, significantly inhibiting the formation and accumulation of hot spots. From a microstructural perspective, this reduces the probability of accidental detonation during production, storage, transportation, and use, comprehensively improving the intrinsic safety performance of energetic materials.

[0039] This invention utilizes a mild reaction pathway of room-temperature liquid-phase ion assembly to prepare graphite-like layered energetic ionic salts by combining nitrogen-rich cations with 3,5-dinitro-1,2,4-triazole anions. This method offers significant advantages such as ease of operation, safety, and environmental friendliness. Furthermore, the method allows for targeted control of crystal stacking structure and properties through flexible replacement of cation and anion ligands, further expanding the structural library of layered energetic salts. Simultaneously, the azole monocyclic anion ligands used can be structurally modified to further enhance the energy density and thermal decomposition temperature of the compounds. The resulting energetic ionic salts exhibit thermal decomposition temperatures exceeding 210℃, mechanical sensitivity far superior to traditional explosives, and excellent detonation performance, making them promising for widespread application in military and civilian fields such as mining, oil exploration, aerospace, engineering blasting, and advanced weaponry.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An energetic ionic salt synthesized from 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation, characterized in that, The energetic ionic salt has a graphite-like layered structure, formed by the planar configuration of 3,5-dinitro-1,2,4-triazole anions and nitrogen-containing cations through hydrogen bonding and π-π stacking interactions to form a two-dimensional mesh-like layered stack.

2. The energetic ionic salt synthesized from 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in claim 1, characterized in that, The crystal density of the energetic ionic salt is 1.623~1.634 g / cm³. 3 Its thermal decomposition temperature is 210~255℃, impact sensitivity is >40J, friction sensitivity is >360N, and detonation velocity is 8152~8655m / s.

3. The energetic ionic salt synthesized from 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in claim 1, characterized in that, The general formula for the energetic ionic salt is [Cation]. m [Anion] n ; where m and n are determined based on the number of Lewis acidic sites and Lewis basic sites, respectively, and take values ​​of 1 or 2.

4. The energetic ionic salt synthesized from 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in claim 1, characterized in that, The nitrogen-containing cations include guanidinium ions and ammonium ions; The molecular formula of the guanidinium ion is: The chemical formula of the energetic ion salt is C3H6N8O4; The molecular formula of the ammonium cation is: The chemical formula of the energetic ionic salt is C2H8N6O6.

5. The energetic ionic salt synthesized from 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in claim 4, characterized in that, Energetic ionic salt C3H6N8O4, monoclinic system, space group C2 / c, density 1.661 g / cm³. 3 Energetic ionic salt C2H8N6O6, triclinic crystal system, space group P-1, density 1.623 g / cm³ 3 .

6. A method for preparing an energetic ionic salt based on the synthesis of a 3,5-dinitro-1,2,4-triazole anion and a nitrogen-containing cation according to any one of claims 1 to 5, characterized in that, It is prepared by solvent heating and solvent diffusion methods based on 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation.

7. The method for preparing an energetic ionic salt based on the synthesis of 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in claim 6, characterized in that, Crystallization of energetic ion salts can be achieved by adjusting the pH value to 6-7 and the temperature to 60-80℃.

8. The method for preparing an energetic ionic salt based on the synthesis of 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in claim 6, characterized in that, The solvent is selected from methanol, ethanol, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, acetone, ethyl acetate and water.

9. The method for preparing an energetic ionic salt based on the synthesis of 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in claim 6, characterized in that, The sources of guanidinium ions and ammonium cations are guanidine carbonate, guanidine bicarbonate, guanidine hydrochloride, guanidine sulfate, guanidine oxalate, ammonia, ammonium chloride, ammonium oxalate, and ammonium sulfate.

10. The application of the energetic ionic salt synthesized from the 3,5-dinitro-1,2,4-triazole anion and nitrogen-containing cation as described in any one of claims 1 to 5, characterized in that, The energetic ionic salt is applied to propellants, explosives, or insensitive pyrotechnics.

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