A green metal-free fused-ring initiating substance

Fused Triazole-Tetrazine Assembled with Different Functional Moieties: Construction of Multipurpose Energetic Materials

Azido, amino, and azo functionalities were introduced into tetrazine backbones to access multifunctional energetic materials. AzNTT demonstrates effective initiation capability (MPC = 50 mg), whereas NTTA balances well between the energy and stability. Azo-functionalized BNTTD has a high density of 1.908 g cm-3, with performance comparable to that of the benchmark material HMX. This work underscores the scope of energetic functionalization and the outstanding comprehensive performance of polycyclic tetrazines.

Self-Assembly Method for Synthesizing High-Dimensional EMOFs with High Stability and Laser Response

Dimension and solvent molecules affect the performance of energetic metal-organic frameworks (EMOFs). High-dimensional EMOFs are usually characterized by high stability and low sensitivity due to their complex network structure. However, solvent molecules affect the detonation performance of EMOFs, and these molecules may be removed at low temperatures, resulting in structural collapse and affecting the stability of EMOFs. In this work, zero-dimensional (0D) Co(AFTO)2·(H2O)2 (EMOF 1) and Ni(AFTO)2·(H2O)2 (EMOF 2) with coordinated water molecules and [Co(AFTO)2]n·EtOH (EMOF 3) and [Ni(AFTO)2]n (EMOF 4) (AFTO = 5-(4-amino-furazan-3-yl)-1-hydroxytetrazole) with high-dimensional structure were synthesized using hydrothermal and self-assembly methods in ethanol, respectively. Structural and performance tests show that EMOF 3 and 4 exhibit remarkable thermal stability and low mechanical sensitivity. This method is a simple, effective, and green technique for synthesizing high-dimensional EMOFs with high stability through self-assembly in ethanol solution. In addition, EMOF 3 and 4 can be used as primary green laser explosives.

Diazotization of o-Aminoamidoximes for the Preparation of Energetic 6,5,6-Fused 1,2,3-Triazine-3-oxides

Two 6,5,6-fused 1,2,3-triazine-3-oxides (4 and 6) were designed and synthesized via the reaction of o-aminoamidoximes with sodium nitrite. In addition, the ring-opening products (5, 7, and 8) derived from 1,2,3-triazine-3-oxides were isolated and characterized. A comprehensive exploration of the reaction mechanism governing the ring-opening process was performed through a combination of theoretical and experimental studies. Notably, compound 4 exhibited commendable detonation properties and low sensitivity, demonstrating its promising potential as an energetic material.

An Intramolecular-Lock Facilitates Planar Tricyclic Fused Energetic Compounds

Exploiting novel fused cyclic frameworks through simple and efficient methods has provided a blueprint for developing advanced explosives. In this study, six new [5,6,5]-tricyclic fused energetic compounds (I-VI) were synthesized through an intramolecular cyclization strategy involving a C-NH2 directed cyclization reaction. The work not only boosts the development of fused cyclic energetic compounds but also highlights their potential applications as secondary or heat-resistant explosives.

Host-Guest Technique for Designing Highly Energetic Compounds with the Nitroamino Group

A new energetic material, 2-azido-4,7-nitroamino-1H-imidazo[4,5-d]pyridazine (ANIP) with a highly sensitive azido group and its host-guest compounds (ANIP/H2O and ANIP/H2O2), and energetic salts were obtained. With the guest and protons in host molecules, an abundant hydrogen bond system can be formed. This results in high crystal density and good sensitivity, which suggests that the host-guest strategy is a promising way to balance the contradiction between energy and sensitivity and provides a new path to obtain a new generation of high energetic materials.

Pushing the Limit of Oxygen Balance on a Benzofuroxan Framework: K2DNDP as an Extremely Dense and Thermally Stable Material as a Substitute for Lead Azide

Because of environmental and health impacts, there is an ongoing necessity to develop sustainable primary explosives to replace existing lead-based analogues. Now we describe a potential primary explosive, dipotassium 4,6-dinitro-5,7-dioxidobenzo[c][1,2,5]oxadiazole 1-oxide (K2DNDP), which exhibits an excellent thermal stability (Tdec = 281 °C), positive oxygen balance (+4.79%), and a calculated crystal density of ρ = 2.274 g cm-3 at 100 K. Its physicochemical properties concomitantly with its straightforward synthesis make it a potential replacement for lead-based initiators.

High-Energy-Density Material with Magnetically Modulated Ignition

Preparation of a redox-frustrated high-energy-density energetic material is achieved by gentle protolysis of Mn[N(SiMe3)2]2 with the perchlorate salt of the tetrazolamide [H2NtBuMeTz]ClO4 (Tz = tetrazole), yielding the Mn6N6 hexagonal prismatic cluster, Mn6(μ3-NTztBuMe)6(ClO4)6. Quantum mechanics-based molecular dynamics simulations of the decomposition of this molecule predict that magnetic ordering of the d5 Mn2+ ions influences the pathway and rates of decomposition, suggesting that the initiation of decomposition of the bulk material might be significantly retarded by an applied magnetic field. We report here experimental tests of the prediction showing that the presence of a 0.5 T magnetic field modulates the ignition onset temperature by +10.4 ± 3.9 °C (from 414 ± 4 °C), demonstrating the first example of a magnetically modulated explosive.

Exploring a Fused Triazole-Tetrazine Binary CN Material for a Promising Initiating Substance

The pursuit of binary carbon-nitrogen (CN) materials with high density and good thermal stability presents a significant challenge due to the inherent trade-off between high-energy storage and low bond dissociation energy. In this study, we designed and synthesized (S)-1,2-bis(3-azido-1H-1,2,4-triazol-1-yl)diazene (BAzTD) and 2,9-diazidobis([1,2,4]-triazolo)[1,5-d:5',1'-f][1,2,3,4]tetrazine (DAzTT) through a straightforward reaction. Remarkably, DAzTT demonstrated a high density of 1.816 g·cm-3 (at 298 K) and a considerable thermal decomposition temperature of 216.86 °C. These properties outperform those of previously reported binary heterocyclic CN compounds and polyazido heterocyclic compounds. The quantum-chemical methods further substantiated the integral role of aromaticity as the driving force behind this difference. Additionally, the initiation capability of DAzTT was evaluated by a notably low minimum primary charge (MPC = 40 mg), surpassing conventional organic primary explosives, such as commercial 2-diazo-4,6-dinitrophenol (DDNP, MPC = 70 mg). The exceptional priming ability highlights the potential as an environmentally friendly replacement for toxic lead azide. DAzTT sets a new standard for binary CN compounds and provides a valuable precursor for high-nitrogen carbon nitride materials.

Construction of High Energy Nanoscale Lead Azide Composite with Improved Flame Sensibility from Intercalated Hydroxide

It is of great significance to develop efficient methods for preparing high-content modified nanoscale lead azide (LA) composites used in microinitiating devices. In this work, a structurally controllable salicylate-intercalated lead hydroxide with a nanoscale mesoporous structure is designed. Using it as a precursor, carbon-based lead azide (LA/C) and salicylate-based lead azide (LA/SA) are fabricated by the gas-solid azidation of the framework (GAF) method within 3 h, greatly reducing the preparation time of nano-LA composites. The characterizations of the composites demonstrate that the Pb in the precursors is transformed into nanoscale LA attached to the salicylate radical or its carbonized skeleton. Due to the unique embedded nanostructures and excellent electrical and thermal conductivity of salicylate-derived carbon materials, LA/C exhibits excellent electrostatic safety (E50 = 0.25 J) and flame sensitivity (H50 = 28 cm). The adjustable organic-inorganic ratio of intercalated hydroxides allows the LA content in LA/C to reach as high as 92.5%, enabling 6.50 mg of LA/C to successfully detonate secondary explosive CL-20 in a microinitiating device, demonstrating an amazing detonation ability superior to other reported LA complexes. The research provides a new perspective for the development of nanoscale LA composites with high LA content and appropriate sensitivity.

A promising perovskite primary explosive

A primary explosive is an ideal chemical substance for performing ignition in military and commercial applications. For over 150 years, nearly all of the developed primary explosives have suffered from various issues, such as troublesome syntheses, high toxicity, poor stability or/and weak ignition performance. Now we report an interesting example of a primary explosive with double perovskite framework, {(C6H14N2)2[Na(NH4)(IO4)6]}n (DPPE-1), which was synthesized using a simple green one-pot method in an aqueous solution at room temperature. DPPE-1 is free of heavy metals, toxic organic components, and doesn't involve any explosive precursors. It exhibits good stability towards air, moisture, sunlight, and heat and has acceptable mechanical sensitivities. It affords ignition performance on par with the most powerful primary explosives reported to date. DPPE-1 promises to meet the challenges existing with current primary explosives, and this work could trigger more extensive applications of perovskite.

Regulating the Coordination Environment by Using Isomeric Ligands: Enhancing the Energy and Sensitivity of Energetic Coordination Compounds

Transforming the energy storage structure is an effective approach to achieve a balance between the detonation performance and the sensitivity of energetic compounds, with a goal of high energy and low sensitivity. Building upon previous work, this study employed an isomeric compound 1H-pyrazole-3-carbohydrazide (3-PZCA) as a ligand and creatively designed the energetic coordination compound (ECC) Ag(3-HPZCA)2(ClO4)3 (ECC-1). It is a novel material with a dual structure of ionic salts and coordination compounds, which represents the first report of such a structure in Ag(I)-based ECCs. With its unique structures, ECC-1 exhibits a larger [ClO4-] content, a higher oxygen balance constant (OB = 0%), and superior mechanical sensitivity (IS = 13 J and FS = 40 N). Theoretical calculations indicate that ECC-1 has a higher detonation performance compared to previous work. Furthermore, the explosive experiment testing results demonstrate that it can be ignited by lower-threshold lasers and possesses excellent initiation capability and explosive power, making it suitable not only as a primary explosive but also as a secondary explosive.

Periodate-Based Perovskite Energetic Materials: A Strategy for High-Energy Primary Explosives

The requirements for high energy and green primary explosives are more and more stringent because of the rising demand in the application of micro initiation explosive devices. Four new energetic compounds with powerful initiation ability are reported and their performances are experimentally proven as designed, including non-perovskites ([H2 DABCO](H4 IO6 )2 ·2H2 O, named TDPI-0) and perovskitoid energetic materials (PEMs) ([H2 DABCO][M(IO4 )3 ]; DABCO=1,4-Diazabicyclo[2.2.2]octane, M=Na+ , K+ , and NH4 + for TDPI-1, -2, and -4, respectively). The tolerance factor is first introduced to guide the design of perovskitoid energetic materials (PEMs). In conjunction with [H2 DABCO](ClO4 )2 ·H2 O (DAP-0) and [H2 DABCO][M(ClO4 )3 ] (M=Na+ , K+ , and NH4 + for DAP-1, -2, and -4), the physiochemical properties of the two series are investigated between PEMs and non-perovskites (TDPI-0 and DAP-0). The experimental results show that PEMs have great advantages in improving the thermal stability, detonation performance, initiation capability, and regulating sensitivity. The influence of X-site replacement is illustrated by hard-soft-acid-base (HSAB) theory. Especially, TDPIs possess much stronger initiation capability than DAPs, which indicates that periodate salts are in favor of deflagration-to-detonation transition. Therefore, PEMs provide a simple and feasible method for designing advanced high energy materials with adjustable properties.

Synthesis of fused energetic compounds using structural modification from local carbonyl to hydroxylamine/hydrazone

This work presents the successful synthesis of a series of fused energetic compounds using the strategy of structural modification from local carbonyl to hydroxylamine, hydrazone or methylamine. Hydroxylamine-substituted compound 2 exhibits high density, high detonation performance and low sensitivities as a secondary explosive.

Regulation of stability and density of energetic materials via isomerism

Selective regulation of stability and density via isomerism is a promising strategy for developing energetic materials. In this work, we selectively introduced dinitromethyl groups at different positions of 4-nitro-1,2,3-triazole. The regional heterogeneity endows a high crystal density by virtue of the dense packing; on the other hand, it changes the charge distribution in the molecule, and reinforces the hydrogen bonding interactions, all of which stabilize the material. The resulting compounds exhibit excellent detonation properties and impact sensitivity that are comparable to those of HMX (D_v = 9250 m s^-1 and IS = 10 J).

Design and Synthesis of Bistetrazole-Based Energetic Salts Bearing the Nitrogen-Rich Fused Ring

A series of bistetrazole-based energetic salts bearing a nitrogen-rich fused ring were designed and synthesized. Among them, compounds 4-10 showed good detonation properties and excellent thermostability. By treating nitrogen-rich fused ring 3 with concentrated hydrochloric acid, a new type of Dimroth rearrangement was observed that afforded compound 12 efficiently. This new transformation herein constitutes a valuable addition to the Dimroth rearrangement.

Thermal stability of azole-rich energetic compounds: their structure, density, enthalpy of formation and energetic properties

Energetic compounds, as a type of special material, are widely used in the fields of national defense, aerospace and exploration. Their research and production have received growing attention. Thermal stability is a crucial factor for the safety of energetic materials. Azole-rich energetic compounds have emerged as a research hotspot in recent years owing to their excellent properties. Due to the aromaticity of unsaturated azoles, many azole-rich energetic compounds have significant thermal stability, which is one of the properties that researchers focus on. This review presents a comprehensive summary of the physicochemical and energetic properties of various energetic materials, highlighting the relationship between thermal stability and the structural, physicochemical, and energetic properties of azole-rich energetic compounds. To improve the thermal stability of compounds, five aspects can be considered, including functional group modification, bridging, preparation of energetic salts, energetic metal-organic frameworks (EMOFs) and co-crystals. It was demonstrated that increasing the strength and number of hydrogen bonds of azoles and expanding the π-π stacking area are the key factors to improve thermal stability, which provides a valuable way to develop energetic materials with higher energy and thermal stability.

Constructing Highly Reliable and Adaptive Primary Explosive Composites for Micro-Initiator Assisting by a Hybrid Template of Metal-Organic Frameworks and Cross-Linked Polymers

Primary explosive, as a reliable initiator for secondary explosives, is the central component of micro-initiators for modern aerospace systems and military operations. However, they are typically prepared as powders, posing potential safety risks because of the inevitable particles scattering issues in the actual working environments. Here, the fabrication of a highly adaptive bulk material of copper azide (CA)-based safe primary explosive for micro-initiators is demonstrated. This bulk material, as derived by a complete azidation reaction of the carbonized metal-organic framework/cross-linked polymer hybrid template, enables the firm embedding of active CA species in a cross-linked carbon network (denoted as CA-C). Interestingly, this CA-C bulk material demonstrates multifarious mechanical stabilities (e.g., good shock and vibration resistance, and anti-overload capacity) in the simulated working conditions. Meanwhile, the CA contents in the CA-C bulk material reached as high as 70.3%, ensuring its detonation power. As a proof of concept, CA-C bulk material assembling in a micro-detonator can efficiently detonate the secondary explosive of CL-20 under laser irradiation. This work hereby advances the fabrication of safe and powerful primary explosives for the fulfillment of safe micro-initiator in a broad range of applications in aerospace systems.

Toward High-Energy and Low-Sensitivity Energetic Materials Based on a Fused [5,5,5,6]-Tetracyclic Backbone

A route for fused [5,5,5,6]-tetracyclic energetic compounds based on the facile cyclization reaction has been explored. Fused [5,5,5,6]-tetracyclic compound 4 shows a high measured density (1.924 g cm^-3), a low sensitivity (IS = 10 J, and FS = 144 N), and an excellent detonation velocity (9241 m s^-1), which are much better than those of RDX. The results indicate that compound 4 is a potential candidate as a secondary explosive and provide new insight into the construction of fused polycyclic heterocycles.

The design and synthesis of new advanced energetic materials based on pyrazole-triazole backbones

A series of derivatives of the nitropyrazole-triazole backbone were designed through units' screening of 219 N-heterocycle compounds and were synthesized. Among them, the thermal stability of DNPAT (T_dec = 314 °C) is close to that of traditional heat-resistant explosive HNS (318 °C) while the detonation performance and sensitivity (D = 8889 m s^-1; IS = 18 J) are better than those of HNS (D = 7612 m s^-1; IS = 5 J) and traditional high-energy explosive RDX (D = 8795 m s^-1; IS = 7.4 J), which is rarely reported in heat-resistant explosives. Moreover, compounds 4 and 6 show excellent performances (IS > 15 J, D > 9090 m s^-1, P > 37.0 GPa), illustrating that compounds 4 and 6 may be used as secondary explosives. All these results enrich prospects for the development of energetic materials.

Transforming agrifood systems in a win-win for health and environment: evidence from organic rice-duck coculture

BACKGROUND

Rice-duck coculture is an ecological agricultural mode; however, the nutritional and environmental benefits of transforming from conventional rice monoculture to rice-duck coculture are unknown. Based on survey data and the life-cycle assessment approach, this study conducted a carbon footprint evaluation of conventional rice monoculture (CR), organic rice monoculture (OR), and organic rice-duck coculture (ORD) using different functional units.

RESULTS

The carbon footprint per hectare of ORD (7842 ± 284 kg CO₂ eq ha^-1 ) was slightly lower than that of CR (7905 ± 412 kg CO₂ eq ha^-1 ), while higher than that of OR (7786 ± 235 kg CO₂ eq ha^-1 ). Although the rice yield of ORD was slightly lower than that of CR, its nutrient density unit (NDU) did not decrease significantly due to the additional duck yield. Thus, the carbon footprint per NDU of ORD was significantly lower than that of OR by 24.3% (P < 0.05) and was 5.8% higher than that of CR, but this was not statistically significant. Due to the higher economic profits of ORD, its unit of carbon footprint per economic profit was significantly reduced (by 47.1-75.7%) compared with the other two farming modes, while the net ecosystem economic budget was significantly increased by 98.5-341.9% (P < 0.05).

CONCLUSION

Transforming from a rice monoculture to a coculture system will contribute to a win-win situation for human health and environmental sustainability. This study highlighted the abundant nutritional output function of the rice-duck coculture and analyzed the urgency and necessity of transitioning from traditional agriculture to ecological agriculture from the production and consumption perspectives. © 2022 Society of Chemical Industry.

A series of N-trinitromethyl-substituted polynitro-pyrazoles: high-energy-density materials with positive oxygen balances

An N-trinitromethyl strategy was employed for the synthesis of polynitro-pyrazole based high-energy-density compounds with great potential as energetic materials. The new compounds were characterized by 1H and 13C NMR, IR spectroscopy, elemental analysis, differential scanning calorimetry, and single-crystal X-ray diffraction. Compound 10 exhibits high energetic properties, has a positive oxygen balance (OB) of +2.1%, and an excellent specific impulse (272.4 s), making it a potential high-energy dense oxidizer to replace AP in solid rocket propellants. The nitration of 7 with HNO3/H2SO4 yielded the green primary explosive 12, which showed higher density, higher performance, better oxygen balance and lower sensitivities to those of currently used diazodinitrophenol. Compound 13 is a nitrogen and oxygen rich secondary explosive with a high OB (+5.0%), comparable energy (D = 9030 m s-1; P = 35.6 GPa; η = 1.03) to HMX, and much lower mechanical sensitivity (IS = 12 J, FS = 240 N).

Construction of Highly Thermostable and Insensitive Three-Dimensional Energetic Salts Based on [1,2,5]Oxadiazolo[3,4-d]pyrimidine

A novel method for accessing energetic salts of a fused-ring skeleton based on [1,2,5]oxadiazolo[3,4-d]pyrimidine and three alkali metals, sodium (Na), potassium (K), and cesium (Cs), was developed. All three compounds were fully characterized, and their structures were confirmed by single-crystal X-ray analysis. They were highly thermally stable (>290 °C) and had high density, good detonation properties, and insensitive properties, which suggested possible heat-resistant explosive applications.

A two-site reactive platform in the synthesis of amino-functionalized amphiphilic molecules via sulfenic acids

The synthesis of some bolaamphiphiles is described. It is a convergent approach that allows the linkage of a glucosyl derivative to a bis-functionalized platform, via a copper-free Sonogashira cross-coupling. The central core was obtained from the reaction of a suitably substituted bis-sulfoxide with diethynyl benzenes. The intermediates of such reaction are sulfenyl functions that are easily added to one triple bond of the unsaturated molecules. The functionalization at the central core, through the nucleophilic addition of ammonia or piperidine onto the two vinyl sulfonyl groups already present in the backbones of the molecules, opened the way to the preparation of more complex derivatives. The observation of the formation of new stereogenic carbons with an unexpected significantly high diastereoselectivity was justified and supported by preliminary theoretical calculations. The two ending glucosyl moieties were favourably deprotected to afford the amino-functionalized bolaamphiphilic molecules.

C-C bonded bis-5,6 fused triazole-triazine compound: an advanced heat-resistant explosive with high energy and low sensitivity

It is still an urgent problem in the field of energetic materials to explore the synthesis of heat-resistant compounds with balanced energy and thermal stability through simple synthetic routes. Recently, fused compounds are considered to provide a promising framework for the construction of ideal heat-resistant compounds. In this study, three novel C-C bonded bis-5,6 fused triazole-triazine compounds, 3,3'-dinitro-[7,7'-bi[1,2,4]triazolo[5,1-c][1,2,4]triazine]-4,4'-diamine (2), 4,4'-diamino-[7,7'-bi[1,2,4]triazolo[5,1-c][1,2,4]triazine]-3,3'-dicarbonitrile (3), and 3,3'-di(1H-tetrazol-5-yl)-[7,7'-bi[1,2,4]triazolo[5,1-c][1,2,4]triazine]-4,4'-diamine (4), were synthesized by a simple method. Compound 2 exhibited an approaching detonation velocity of 8837 m s^-1 compared with that of the traditional high energy explosive RDX velocity of 8795 m s^-1, while its thermal stability (T_d = 327 °C) was comparable to that of the heat-resistant explosive HNS (T_d = 318 °C). At the same time, the double fused compound 2 also realized high density (1.90 g cm^-3) and extremely low sensitivity (FS > 360 N, IS > 40 J). The above good comprehensive properties prove that compound 2 can be used as a potential insensitive high-energy heat-resistant explosive. In addition, the effects of the crystal structure on the sensitivity and thermal stability were studied using the quantum chemical methods. These results imply that the formation of double fused ring compounds by the ring closing reaction at symmetrical positions is an ideal strategy for the development of advanced heat-resistant explosives.

Series of Azido and Fused-Tetrazole Explosives: Combining Good Thermal Stability and Low Sensitivity

The introduction of azido groups into the energetic skeleton has the advantages of increasing the energy level. In this work, a series of azido compounds with good stability and low sensitivity as well as tetrazole-fused compounds based on energetic salts are synthesized. The detonation pressures and velocities of these new compounds fall in the ranges of 18.9-27.3 GPa and 7153-8450 m s^-1, respectively. The detonation velocity of the tetrazole-fused compounds based on the potassium salts 3, 6, and 7 are 7810, 7153, and 7989 m s^-1, respectively. Also, their decomposition temperatures (244, 237, and 240 °C, respectively) are higher than that of traditional explosive RDX (204 °C). Notably, two representative compounds 2 and 5 possess higher decomposition temperature (2: 196 °C and 5: 178 °C) and overall detonation properties (2: D = 8129 m s^-1 and P = 26.6 GPa and 5: D = 8336 m s^-1 and P = 27.3 GPa) as well as relativity lower sensitivities (2: IS = 12 J and FS = 240 N and 5: IS = 10 J and FS = 144 N) than that of primary explosive 2-diazo-4,6-dinitrophenol (T_d = 157 °C, D = 6900 m s^-1, P = 24.7 GPa, IS = 1 J, and FS = 24.7 N). Moreover, the initiation capacity of compounds 2 and 5 was also assessed through the initiation tests. The results indicate that the two compounds could be a promising environmentally friendly primary explosive.

2-(1,2,4-triazole-5-yl)-1,3,4-oxadiazole as a novel building block for energetic materials

The exploration of novel nitrogen-rich heterocyclic building blocks is of importance in the field of energetic materials. A series of 2-(1,2,4-triazole-5-yl)-1,3,4-oxadiazole derivatives based on a new energetic skeleton have been first synthesized by a simple synthetic strategy. All three compounds are well-characterized by IR spectroscopy, NMR spectroscopy and thermal analysis. The compounds 5 and 8 are further characterized by single-crystal X-ray diffraction analysis. 8 and its salts (8a-8c) possess relative high decomposition temperature and low sensitivity, while 5 exhibits low decomposition temperature and high sensitivity. According to EXPLO5 calculation results of detonation performance, both 5 and 8 display acceptable detonation velocities (D) of 8450 m/s and 8130 m/s and detonation pressures (P) of 31.6 GPa and 29.2 GPa, respectively. Furthermore, 5 containing a rare diazonium ylide structure shows high impact sensitivity (4.5 J), making it has a potential as a primary explosive.

Facile Synthesis of Energetic Nanoparticles of Copper Azide with High Initiation Ability for Micro-Initiator Applications Using Layered Copper Hydroxide

Copper azide (CA) is one of the preferred primary explosives in the micro-initiating device, and it is of conducive significance to develop high-content CA-modified materials. In this work, we reported two types of CA composites with CA nanorods embedded in carbon nanosheets (CA/C) and CA distributed on salicylic acid (CA/SA) using layered copper hydroxide nanosheets intercalated with salicylic acid as the precursor. The detailed characterizations demonstrated that CA/C exhibits eximious electrostatic sensitivity (1.06 mJ) due to the inherent structural characteristics of CA/C such as the limitation of the free movement of CA by the layered structure and preeminent electrical conductivity of carbon nanosheets. Surprisingly, CA/C with nearly 1.0 mg in the miro-initiating device can reliably detonate Hexanitrohexaazaisowurtzitane (CL-20). CA/C exhibits extremely high CA content (93%), excellent ignition ability, and detonation ability, and its performance is superior to pure CA and most CA-modified materials reported previously. CA/SA also has an excellent detonation ability and its electrostatic sensitivity is as low as 0.92 mJ. These findings provide a new perspective for the development of high-performance primary explosives for the micro-initiating device.

Copper Azide Nanoparticle-Encapsulating MOF-Derived Porous Carbon: Electrochemical Preparation for High-Performance Primary Explosive Film

It is highly desired but still remains challenging to design a primary explosive-based nanoparticle-encapsulated conductive skeleton for the development of powerful yet safe energetic films employed in miniaturized explosive systems. Herein, a proof-of-concept electrochemical preparation of metal-organic frameworks (MOFs) derived porous carbon embedding copper-based azide (Cu(N₃ )₂ or CuN₃ , CA) nanoparticles on copper substrate is described. A Cu-based MOF, i.e., Cu-BTC is fabricated based on anodized Cu(OH)₂ nanorods, as a template, to achieve CA/C film through pyrolysis and electrochemical azidation. Such a CA/C film, which is woven by numerous ultrafine nanofibers, favorably demonstrates excellent energy release (945-2090 J g^-1 ), tunable electrostatic sensitivity (0.22-1.39 mJ), and considerable initiation ability. The performance is superior to most reported primary explosives, since the CA nanoparticles contribute to high brisance and the protection of the porous carbon network. Notably, the growth mechanism of the CA/C film is further disclosed by detailed experimental investigation and density functional theory (DFT) calculation. This work will offer new insight to design and develop a CA-based primary explosive film for applications in advanced explosive systems.

Full-nitro-nitroamino cooperative action: Climbing the energy peak of benzenes with enhanced chemical stability

More nitro groups accord benzenes with higher energy but lower chemical stability. Hexanitrobenzene (HNB) with a fully nitrated structure has stood as the energy peak of organic explosives since 1966, but it is very unstable and even decomposes in moist air. To increase the energy limit and strike a balance between energy and chemical stability, we propose an interval full-nitro-nitroamino cooperative strategy to present a new fully nitrated benzene, 1,3,5-trinitro-2,4,6-trinitroaminobenzene (TNTNB), which was synthesized using an acylation-activation-nitration method. TNTNB exhibits a high density (d: 1.995 g cm^-3 at 173 K, 1.964 g cm^-3 at 298 K) and excellent heat of detonation (Q: 7179 kJ kg^-1), which significantly exceed those of HNB (Q: 6993 kJ kg^-1) and the state-of-the-art explosive CL-20 (Q: 6534 kJ kg^-1); thus, TNTNB represents the new energy peak for organic explosives. Compared to HNB, TNTNB also exhibits enhanced chemical stability in water, acids, and bases.

Polynitro-Functionalized Azopyrazole with High Performance and Low Sensitivity as Novel Energetic Materials

The development of energetic materials is still facing a huge challenge because the relationship between energy and sensitivity is usually contradictory: high energy is always accompanied with low sensitivity. Here, a high-energy, low-sensitivity energetic polynitro-functionalized azopyrazole (TNAP) and its energetic salts have been synthesized. The structural characterization of these compounds was analyzed by elemental analysis, ¹H and ¹³C NMR spectroscopies, and infrared spectroscopy. The single-crystal structure of compounds K₂TNAP, TNAP, 5, and 6 was obtained by X-ray diffraction, and K₂TNAP is a novel energetic metal-organic framework. The calculated detonation properties of TNAP (9040 m s^-1 and 36.0 GPa) are superior to that of RDX (8796 m s^-1 and 33.6 GPa). In addition, TNAP also has lower mechanical sensitivity (IS > 40 J, FS = 244 N) and higher decomposition temperature (T_d = 221 °C) than RDX (IS = 7.4 J, FS = 120 N, and T_d = 204 °C). These experimental results suggest that TNAP may become a new candidate for secondary explosives.

Cobalt Metal-Organic Frameworks with Aggregation-Induced Emission Characteristics for Fluorometric/Colorimetric Dual Channel Detection of Nitrogen-Rich Heterocyclic Compounds

Nitrogen-rich heterocyclic compounds (NRHCs) are an emerging type of explosive, and their quantification is important in national security inspection and environmental monitoring. Up until now, designing an efficient NRHCs sensing strategy was still in the early stages. Herein, a new metal-organic framework (MOF) with aggregation-induced emission (AIE) characteristics is synthesized with fluorometric/colorimetric responses for rapid and selective detection of NRHCs. The nonemissive probe is designed with tetraphenylethylene derivative as the linker and Co as the node, quencher, and color-changing agent. Cobalt AIE-MOF exhibits a turn-on emission enhancement due to the competitive coordination substitution between NRHCs and the scaffold as well as the following AIE process of the liberative linkers. Meanwhile, the color appearance of the probe changes from blue to yellow based on the dissociation of the original Co coordinating system. Using this dual-mode probe, single- and dual-ring NRHCs are successfully detected from 5 μM to 7.5 mM within 25 s. The cobalt AIE-MOF exhibits excellent selectivity of NRHCs against a variety of interferences, providing a promising tool for designing a multichannel detection strategy.

Krapcho Decarboxylation of Ethyl-Carbazate: Synthetic Approach toward 1,1'-Diamino-5,5'-bistetrazole and Its Utilization as a High-Performing Metal-Free Initiator

1,1'-Diamino-5,5'-bistetrazole (C₂H₄N₁₀), a highly nitrogen-containing compound with promising energetic characteristics, is available through a classic organic reaction protocol applied on an inorganic azole system. This is the only Krapcho reaction on a carbamate system described in the literature so far. 1,1'-Diamino-5,5'-bistetrazole was extensively characterized through multinuclear spectroscopy, mass spectrometry, thermal analysis, and X-ray diffraction. The sensitivity values were measured, and detonation values were calculated. Its capability to initiate pentaerythritol tetranitrate (PETN) was successfully demonstrated.

Silver(I)-Based Molecular Perovskite Energetic Compounds with Exceptional Thermal Stability and Energetic Performance

In recent years, molecular perovskite energetic materials have attracted more attention because of their simple synthesis processes, high thermal stabilities, excellent performances, and great significance as a design platform for energetic materials. To explore the possibility of the application of molecular perovskite energetic materials in heat-resistant explosives, four silver(I)-based molecular perovskite energetic compounds, (H₂A)[Ag(ClO₄)₃], where H₂A = piperazine-1,4-diium (H₂pz²⁺) for PAP-5, 1-methyl-piperazine-1,4-diium (H₂mpz²⁺) for PAP-M5, homopiperazine-1,4-diium (H₂hpz²⁺) for PAP-H5, and 1,4-diazabicyclo[2.2.2]octane-1,4-diium (H₂dabco²⁺) for DAP-5, were synthesized by a one-pot self-assembly strategy and structurally characterized. The single-crystal structures indicated that PAP-5, PAP-M5, and DAP-5 possess cubic perovskite structures while PAP-H5 possesses a hexagonal perovskite structure. Differential thermal analyses showed that their onset decomposition temperatures are >308.3 °C. For PAP-5 and DAP-5, they have not only exceptional calculated detonation parameters (D values of 8.961 and 8.534 km s^-1 and P values of 42.4 and 37.9 GPa, respectively) but also the proper mechanical sensitivity (impact sensitivities of ≤10 J for PAP-5 and 3 J for DAP-5 and friction sensitivities of ≤5N for both PAP-5 and DAP-5) and thus are of interest as potential heat-resistant primary explosive components.

Modulating Energetic Characteristics of Multicomponent 1D Coordination Polymers: Interplay of Metal-Ligand Coordination Modes

The energetic properties of multicomponent explosive materials can be altered for high detonation capabilities and minimized safety risk by changing their building components. We synthesized energetic coordination polymers (ECPs) using a 5,5'-bis(tetrazole)-1,1'-diolate linker and a N,N-dimethylacetamide (DMA) solvent, together with Cu and Mn metal cations. The new compounds, ECP-1 and ECP-2, contain two different types of 1D chain structures, straight and helical. We have conducted comprehensive studies on these ECP structures, energetic properties, and sensitivity and found excellent insensitivity owing to the long chain-to-chain distances created by the DMA solvent molecules. The results indicate that the metals as well as solvents used are crucial components influencing both the structure and energetic properties.

Fabrication of nanoscale core–shell structured lead azide/porous carbon based on a metal–organic framework with high safety performance

Carbon-based lead azide with nano-scale lead azide coated with a carbon shell (LA/C) was prepared using a lead-containing MOF material. The prepared LA/C exhibits excellent electrostatic sensitivity (1.84 J), higher LA content (85%), and better ignition ability (22 cm) compared to other reported modified LA materials.

Synthesis of heterocyclic (triazole, furoxan, furazan) fused pyridazine di-N-oxides via hypervalent iodine oxidation

Use of a mild PIDA oxidation strategy to access heterocyclic (triazole, furoxan, furazan) fused pyridazine di-N-oxides.

Detonation performance enhancement through a positional isomerism modification strategy

The design, synthesis, physical properties, and calculated detonation performances of two skeleton isomeric energetic compounds containing tetrazole were introduced. By changing the chemical modification sites of the original fused-pyrimidine skeleton,...