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A new strategy for hybrid deep eutectic solvents (DESs) that are hypergolic with hydrogen peroxide is developed, in which the introduction of transition metal components can effectively release the latent and generally unrecognized flammability of common DESs. This strategy illustrates a uniquely modular platform to develop cost-effective and green propellants. [ABSTRACT FROM AUTHOR]

Energetic isomers often exhibit different properties. To understand the effect of arrangement and connection of isomers on energetic properties and sensitivity, in this study, we designed and synthesized a series of oxadiazole nitramine compounds including N-(5-(5-(nitramino)-1,3,4-oxadiazol-2-yl)-1,2,4-oxadiazol-3-yl)nitramide (NOON) and its ionic derivatives. NOON exhibits comparable performance (D = 8888 m s−1, P = 34.1 GPa) to highly explosive RDX. A comparative study of detonation properties, sensitivity, and thermal stability of the three oxadiazole nitramine isomers (NOON, ICM-101, and DNBO) is carried out. The results show that due to the proton transformation, strong intramolecular hydrogen bonding interaction, and formation of six-membered ring conformation, the 2-nitramino-1,3,4-oxadiazole building block exhibits better detonation properties and higher thermal stability than its isomer 2-nitramino-1,2,4-oxadiazole. [ABSTRACT FROM AUTHOR]

With the growth of chemical data, computation power and algorithms, machine learning-assisted high-throughput virtual screening (ML-assisted HTVS) is revolutionizing the research paradigm of new materials. Herein, a combined ML-assisted HTVS and experimental approach was applied to accelerate the search for energetic melt-castable materials with promising properties. The ML-assisted HTVS system is composed of high-throughput molecular generation (in a heuristic enumeration method) and five machine learning-based property prediction models (including density, melting point, decomposition temperature, detonation velocity, and detonation pressure). Using this system, we rapidly targeted 136 promising candidates from a generated molecular space containing 3892 molecules. With extensive efforts on experimental synthesis, eight new energetic melt-castable materials (MC-1 to MC-8) were obtained, and their measured properties were in good agreement with the predicted results. This work verifies the effectiveness of the combined ML-assisted HTVS and experimental approach for the accelerated discovery of energetic melt-castable materials. [ABSTRACT FROM AUTHOR]

The combination of Energetic Ionic Liquid (EIL) "green" fuels and high test peroxide (>90% H2O2; HTP), as a "green" oxidizer, is a very promising platform for the development of fully "green" bipropellants for space exploration. In this work, two new "tandem-action" promoters – [FcCH2N(CH3)3+]2[Cu2I42−] (P1) and [FcCH2N(CH3)3+]n[Cu2I3−]n (P2) – and two reference "single-action" promoters, [FcCH2N(CH3)3+][H3BCN−] (P3) and [CH3N(CH2CH3)3+]n[Cu2I3−]n (P4), were prepared, comprehensively characterized and evaluated for their ability to significantly shorten the Ignition Delay (ID) times of hypergolic reactions between a series of EILs and H2O2. These promoters exhibited high solubility and long-term chemical stability in a typical EIL fuel – 1-ethyl-3-methylimidazolium dicyanamide (F1). Upon screening the performance of promoter–EIL formulations, the best ID result of 31 ms was observed for the combination of 1-ethyl-3-methylimidazolium cyanoborohydride (F2) fuel and promoter P2 (10 wt%), with H2O2 (95%), whereas an ID time of 58 ms was observed for the F2/P2 formulation with commercially available H2O2 (70%), respectively. Remarkably, the latter formulation remained fully homogeneous even at −40 °C, and showed an ID time of 66 ms at this temperature with H2O2 (95%), indicating the advantages of our approach for the development of novel fully "green" bipropellants. [ABSTRACT FROM AUTHOR]

Energetic materials with a graphite-like crystal structure always demonstrate better energy-sensitivity balance than the common ones. However, the knowledge on how to design a graphite-like energetic material is still limited and a rational design procedure for graphite-like energetic materials is much desired. Here, a set of systematic methods for discovering new graphite-like energetic materials is presented. We analyzed the intermolecular self-assembled behavior of graphite-like energetic materials and proposed a combined method of coplanar configuration searching (CCS) and point-chain-plane progressive intermolecular assembly (pcp-PIA) to predict and screen new graphite-like energetic materials. Furthermore, with a self-established high-throughput design system, we rapidly focused on a potential graphite-like energetic molecule (namely, 2-azido-5-nitropyrimidine-4,6-diamine, DANAP) from 426 candidates and finally experimentally verified its graphite-like crystal structure. We believe that the method presented here will have potential applications in guiding the crystal engineering of graphite-like energetic materials, thereby accelerating the discovery of new energetic materials with promising properties. [ABSTRACT FROM AUTHOR]

The crystal structures and stability of energetic compounds are closely related to the energy, safety and reliability of weapons. Searching for new solid forms of an energetic compound has become an integral part of its development. The studied compound, carbonic dihydrazidinium bis[3-(5-nitroimino-1,2,4-triazolate)] (CBNT), is a recently synthesized high energy and low sensitivity energetic ionic salt with promising applications. Herein, we have investigated the crystal structure evolution and searched for new solid forms of CBNT under different conditions via the solvent induction method. The phase composition of all screened samples was analysed by powder or single-crystal X-ray diffraction. Four new solid forms of CBNT·2H2O (1), H2BNT·2DMSO (2), H2BNT·2H2O (3) and [NH2(CH3)2+]2[BNT2−]·2H2O (4) (BNT2− = bis[3-(5-nitroimino-1,2,4-triazolate)2−]) were obtained from water, DMSO, BL/H2O and DMF/H2O, respectively. Their molecular interactions were analysed by theoretical simulations of the Hirshfeld surface and molecular electrostatic potentials. Furthermore, the energetic properties have been verified through EXPLO5. [ABSTRACT FROM AUTHOR]

A new design strategy for zwitterionic energetic materials was developed, and two gem-dinitromethyl functionalized 5-amino-1,3,4-oxadiazolate inner salts were synthesized and characterized. Compared with common energetic salt analogues, both zwitterionic energetic compounds exhibited higher densities, better detonation performances, and comparable mechanical sensitivities. This design strategy may stimulate the development of additional zwitterionic energetic materials. [ABSTRACT FROM AUTHOR]

In the development of advanced high-energy-density materials (HEDMs), the traditional strategy of integrating oxidant and fuel components into an organic molecule makes it very difficult to balance the energy and safety of materials. Herein, we present an intermolecular host–guest inclusion strategy for constructing advanced HEDMs with well-balanced energy and safety. By gradually introducing high-energy oxidants into the supramolecular voids of the deliberately selected energetic host crystal, three host–guest inclusion HEDMs (i.e., HGI-1, HGI-2 and HGI-3) were prepared, which show detonation performances separately comparable to those of three classical HEDMs, namely RDX, HMX and ε-CL-20, but with mechanical sensitivities that are much superior to those of these classical HEDMs. In addition, these self-assembled HEDMs have excellent combustion properties and exhibit great potential as high-energy low signature propellants. This presented host–guest inclusion strategy shows enormous potential for tailoring the energy and sensitivity of energetic materials and will accelerate the development of advanced HEDMs in the future. [ABSTRACT FROM AUTHOR]

New derivatization reactions of 1,1-diamino-2,2-dinitroethylene (FOX-7) are explored, which afford three cyclic triazinane-based energetic compounds 1, 2 and 3 featuring the FOX-7 backbone. Their structures were characterized by X-ray single crystal diffraction analysis. Among them, compound 1 shows a high detonation performance (vD: 8899 m s−1, P: 35.83 GPa) comparable to that of FOX-7. Compound 2 exhibits a good detonation performance (vD: 8332 m s−1, P: 26.47 GPa) and good thermal stability (Td = 188 °C), which is superior to that of most FOX-7-derived energetic compounds. Both of them inherit the low-sensitivity characteristic of FOX-7 because of strong inter- and intra-molecular hydrogen bonds. The presented derivatization reaction has contributed to the ever-expanding chemistry of FOX-7. [ABSTRACT FROM AUTHOR]

Protonated g-C3N4 nanosheets were prepared by refluxing a mixture containing g-C3N4 and 95% H2SO4 at 80 °C for 1 hour. The obtained g-C3N4 nanosheets showed a similar layer structure to that of g-C3N4 and high water adsorption capacities. They also depicted superior conductivities reaching up to 1.44 × 10−2 S cm−1 at 80 °C and 98% RH, with promising features for proton conductivity materials. [ABSTRACT FROM AUTHOR]

A novel fused-ring polynitro compound (5) and a cyclic compound featuring gem-dinitromethylene and nitroso groups (7) were synthesized from 1,1-diamino-2,2-dinitroethylene (FOX-7). Both compounds exhibit high density, decent thermal stability, high detonation performances, and low mechanical sensitivities. This newly developed derivatization strategy enriches the ever-expanding reactive chemistry of FOX-7. [ABSTRACT FROM AUTHOR]

In this work, we prepared and comprehensively characterized four novel iodocuprate-containing ionic liquids, CuILs 1–4. In addition to their interesting molecular structures and physical properties CuILs exhibited capability to efficiently promote hypergolic reactions between boron-containing [EMIM+][H3BCN−] and [MIM]·[BH3] fuels and a highly concentrated H2O2 (95%) oxidizer. The most promising promoter CuIL 3 has the decomposition temperature well above the decomposition temperature of the fuels, was stable in promoter-in-fuel mixtures for weeks and showed ignition delay times down to 14 ms. We believe that further development of our new iodocuprate ionic liquids can lead to promising “green” H2O2-based bipropellant systems for space applications. [ABSTRACT FROM AUTHOR]

A number of energetic ionic liquids (EILs) have been reported as promising hydrazine-replacement fuels for hypergolic rocket propulsion. However, most of these EILs were ignited using corrosive and hazardous concentrated fuming nitric acid. Very significant efforts were recently made to utilize “rocket grade” highly concentrated H2O2 (＞90%) as a “green” alternative to fuming nitric acid and N2O4 oxidizers. Although “rocket grade” H2O2 is more challenging to use and less safe for storage than commercially available H2O2 (70%), the latter is not considered as a viable oxidizer for hypergolic propulsion. In this work, we focused on the development of novel iodine-rich promoters, capable of initiating hypergolic ignition reactions between a typical EIL fuel – 3-ethyl-1-methyl-1H-imidazol-3-ium cyanotrihydroborate – and H2O2. Among the prepared and evaluated promoters, the top performing [FcCH2NEtMe2+]2[B12I122−] compound 5 showed ignition delay times of 45 ms in the reaction of the tested EIL with H2O2 (70%) and 17 ms with H2O2 (95%). We believe that these findings provide a platform for the development and utilization of commercially available H2O2 as a potential “green” oxidizer for rocket propulsion. [ABSTRACT FROM AUTHOR]

A novel derivatization strategy was developed for the exciting reactive chemistry of FOX-7. The as-synthesized FOX-7-derived polynitro compounds exhibited high crystal densities, excellent detonation performances, and good impact and friction sensitivities. This study opens a new path for the ever-expanding chemistry of FOX-7. [ABSTRACT FROM AUTHOR]

Two new metal phosphates, namely, Zn(HPO4)(dl-C3H7NO2) (SCU-4) and In(HPO4)(H2PO4)(dl-C3H7NO2) (SCU-12), were prepared in the presence of the amino acid l-alanine. SCU-4 has a ladderlike structure with edge-sharing 4-rings. SCU-12 represents the first example of a three-dimensional metal phosphate templated by an amino acid. It remains stable in boiling water and shows a high proton conductivity at room temperature under 98% relative humidity. [ABSTRACT FROM AUTHOR]

A series of 1,2,4-oxadiazole-derived energetic compounds were successfully synthesized using 1,2,4-oxadiazole-3-chloroxime as a versatile starting material. These energetic compounds were fully characterized by NMR spectroscopy, IR spectroscopy, and elemental analysis. The structures of compounds 5, 6a, 6c, 8 and 8a were determined by single crystal X-ray diffraction. The physicochemical and energetic properties of all the synthesized energetic compounds, including density, thermal stability and energetic performance (e.g., detonation velocities and detonation pressures) were investigated. Among these energetic compounds, hydrazinium salts 6b and 8b and hydroxylammonium salts 6c and 8c exhibit satisfactory calculated detonation performances, which outperform the commonly used high explosive RDX. Potassium salt 5 shows good detonation performance, high density as well as high sensitivity, making it a potential primary explosive. Compound 9 is a potential candidate for melt-cast explosives due to its remarkable liquid range between melting point (Tm = 98 °C) and decomposition temperature (Td = 208 °C). [ABSTRACT FROM AUTHOR]

A series of C–N linked bistetrazolate nitramino compounds, i.e., 1-(2H-tetrazol-5-yl)-5-nitraminotetrazole (2) and its energetic salts (3–8), were successfully prepared from readily available 5-aminotetrazole. All new energetic compounds were fully characterized by IR and NMR spectra and elemental analysis, and six of them (1, 3–7) were further determined by single-crystal X-ray diffraction analysis. The nitrogen contents of these energetic bistetrazolate compounds, ranging from 59.3% (3) to 74.8% (7), are much higher than those of the commonly used high explosives such as RDX (N: 37.8%), HMX (N: 37.8%) and CL-20 (N: 38.3%). And theoretical calculations by using the Gaussian 09 program package demonstrate that compounds 1–8 have high positive heats of formation, of which the heats of formation of ammonium salt 4 (3.60 kJ g−1), aminonitroguanidinium 5 (3.11 kJ g−1) and dihydrazinium salt 7 (3.25 kJ g−1) are approximately eight times higher than those of RDX (0.39 kJ g−1) and HMX (0.39 kJ g−1), and four times higher than that of CL-20 (0.83 kJ g−1). The high nitrogen contents and high heats of formation have endowed these energetic compounds with prominent detonation performance. It is noteworthy that compound 7 exhibits an excellent calculated detonation velocity of 9822 m s−1 superior to that of CL-20 (9730 m s−1), while the impact and friction sensitivities of 7 (IS = 8 J, FS = 192 N) are comparable to those of HMX (IS = 7 J, FS = 112 N). The good detonation properties with moderate sensitivities demonstrate that compound 7 is a promising candidate for application as a high-performance energetic material. [ABSTRACT FROM AUTHOR]

A luminescent heterometallic MOF with an interrupted cap topology was synthesized and characterized. This compound exhibits a strong blue-light emission and shows naked-eye selective detection toward trinitrobenzene (TNB) even in the presence of other nitro explosives. Furthermore, the compound is also capable of selectively sensing nitroaromatic picric acid (PA) based on the fluorescence quenching mechanism. [ABSTRACT FROM AUTHOR]

In this study, a series of high-energy-density materials (1·2H2O–9) based on N-(3-nitro-1-(trinitromethyl)-1,2,4-triazol-5-yl)nitramide were synthesized and structurally characterized using 1H NMR, 13C NMR, IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. The crystal results demonstrated that potassium 3-nitro-5-(nitroimino)-1-(trinitromethyl)-1,2,4-triazolate hydrate (2·H2O) exhibits an infinite two-dimensional (2D) metal–organic framework (MOF) containing the coordination group NO2 and metal cation K+. Additionally, this 2D MOF exhibited a high oxygen content (46.41%) and a positive oxygen balance (14.77%). Heats of formation and the detonation properties of the newly prepared compounds were calculated using the Gaussian 09 and EXPLO 5 programs, respectively. Energetic evaluation indicated that these compounds demonstrate good detonation performances, all of which outperform traditional primary explosives mercury fulminate, lead azide, 2-diazo-4,6-dinitrophenol, and in some cases, even exceed the performance of high explosive RDX. Therefore, the high detonation parameters of the compounds enable these potential primary explosives to trigger the whole detonation easily. Furthermore, several attractive properties, such as an excellent density (2.00 g cm−3), an impact sensitivity of 2 J, a friction sensitivity of 32 N, and a low amount of toxic detonation products, make 2·H2O an eco-friendly primary explosive. [ABSTRACT FROM AUTHOR]

Two new beryllium phosphite anionic open-frameworks based on Be3P4O12H4 cluster building blocks, formulated as (Him)2·Be3(HPO3)4, were synthesized under solvothermal conditions, where im is imidazole. Interestingly, the use of different alcohols, i.e., isopropanol and n-propanol, as solvents afforded two new anionic open-frameworks with the same chemical composition, but different structures. Compound 1 crystallized in the monoclinic C2/c space group, whereas compound 2 crystallized in the triclinic P1̅ space group. Both compounds displayed intersected channels with 8-, 8-, 8-, and 12-membered windows along different directions. Considering Be3P4O12H4 clusters as four-connected nodes, both compounds showed a pcu topology. Notably, the frameworks of both open-frameworks remained stable after soaking in boiling water for one month. Furthermore, compound 1 exhibited a high proton conductivity of 2.03 × 10−3 S cm−1 at 363 K and 98% relative humidity, indicating its potential as a hydrothermally stable proton-conducting material. [ABSTRACT FROM AUTHOR]

A series of three-dimensional fluorescent heterometallic MOFs based on rod- and cluster-like building blocks were readily prepared under solvothermal conditions. Among them, compounds 1–4 were constructed from rod-like building blocks {Cd–O–M}n (M = Na, K, Na–K, and Mg) and BDC2− ligands, featuring right-hand and left-hand channels with a cap topology. The framework charges of 1–4 can be tuned from negative to neutral via a strategy of changing the secondary metal centre (Na+, Na+–K+, K+ and Mg2+). It is worth noting that the rod-like building block of compound 2 contained three types of metal ion centres (Cd2+, Na+ and K+). Different from compounds 1–4, the topology of 5 changed from a cap net to a 610 net in the presence of Ca2+ as a secondary metal centre. Interestingly, the anionic framework of 5 features two types of linear trinuclear clusters as the building blocks, i.e. {Cd2CaO17} and {Cd2CaO16}, which are relatively rare in known heterometallic open frameworks. Moreover, fluorescent compound 5 with a microporous structure displayed sensing properties towards some nitro-containing compounds, suggesting its potential application as a fluorescent sensor for the sensitive detection of explosives. [ABSTRACT FROM AUTHOR]

Two new open-framework beryllium phosphates, formulated as MV·Be2(HPO4)2(H2PO4)2 (1) and EV·Be2(HPO4)2(H2PO4)2 (2), have been synthesized under solvothermal conditions, where MV = methylviologen and EV = ethylviologen. The two compounds have large 16-membered ring (16 MR) channels with a zeolitic CrB4 topology. They contain in situ generated viologen dications from the alkylation of 4,4′-bipyridine (4,4′-bpy) molecules as the structure-directing agents (SDAs). In comparison, the use of 4,4′-bpy and 2,2′-bpy as the SDAs results in the formation of two different open-framework compounds, (4,4′-H2bpy)2·Be5(HPO4)7 (3) and (2,2′-H2bpy)0.5·Be3(OH)(HPO4)3 (4). Compounds 3 and 4 have different framework structures with 12 MR channels. The presence of large 41084124 cages in the structure of 3 is worth noting. [ABSTRACT FROM AUTHOR]

Energetic isomers often exhibit different properties. To understand the effect of arrangement and connection of isomers on energetic properties and sensitivity, in this study, we designed and synthesized a series of oxadiazole nitramine compounds including N -(5-(5-(nitramino)-1,3,4-oxadiazol-2-yl)-1,2,4-oxadiazol-3-yl)nitramide (NOON) and its ionic derivatives. NOON exhibits comparable performance ( D = 8888 m s -1 , P = 34.1 GPa) to highly explosive RDX. A comparative study of detonation properties, sensitivity, and thermal stability of the three oxadiazole nitramine isomers (NOON, ICM-101, and DNBO) is carried out. The results show that due to the proton transformation, strong intramolecular hydrogen bonding interaction, and formation of six-membered ring conformation, the 2-nitramino-1,3,4-oxadiazole building block exhibits better detonation properties and higher thermal stability than its isomer 2-nitramino-1,2,4-oxadiazole.

A new design strategy for zwitterionic energetic materials was developed, and two gem-dinitromethyl functionalized 5-amino-1,3,4-oxadiazolate inner salts were synthesized and characterized. Compared with common energetic salt analogues, both zwitterionic energetic compounds exhibited higher densities, better detonation performances, and comparable mechanical sensitivities. This design strategy may stimulate the development of additional zwitterionic energetic materials.

Protonated g-C3N4 nanosheets were prepared by refluxing a mixture containing g-C3N4 and 95% H2SO4 at 80 °C for 1 hour. The obtained g-C3N4 nanosheets showed a similar layer structure to that of g-C3N4 and high water adsorption capacities. They also depicted superior conductivities reaching up to 1.44 × 10-2 S cm-1 at 80 °C and 98% RH, with promising features for proton conductivity materials.

A series of 1,2,4-oxadiazole-derived energetic compounds were successfully synthesized using 1,2,4-oxadiazole-3-chloroxime as a versatile starting material. These energetic compounds were fully characterized by NMR spectroscopy, IR spectroscopy, and elemental analysis. The structures of compounds 5, 6a, 6c, 8 and 8a were determined by single crystal X-ray diffraction. The physicochemical and energetic properties of all the synthesized energetic compounds, including density, thermal stability and energetic performance (e.g., detonation velocities and detonation pressures) were investigated. Among these energetic compounds, hydrazinium salts 6b and 8b and hydroxylammonium salts 6c and 8c exhibit satisfactory calculated detonation performances, which outperform the commonly used high explosive RDX. Potassium salt 5 shows good detonation performance, high density as well as high sensitivity, making it a potential primary explosive. Compound 9 is a potential candidate for melt-cast explosives due to its remarkable liquid range between melting point (T m = 98 °C) and decomposition temperature (T d = 208 °C).

Presented here are two novel open-framework cobalt sulfate-oxalates constructed from molecular and chain-like building blocks. The two compounds have different structures: an hcb-type layer with 20-ring windows and a mog-type framework with 12-ring channels. Amine molecules play dual roles in the two structures: as a chelating ligand and a charge-balancing agent.