Fabrication of Energetic Metal-Organic Frameworks: Potassium 5-Carboxylato-3,4-Dinitropyrazole and Potassium 5-(Hydrazinecarbonyl)-3,4-Dinitropyrazole.

Energetic materials have been widely applied in civil and military fields, whose thermostability is a key indicator to evaluate their safety levels under severe conditions. Herein, two novel energetic metal-organic frameworks (EMOFs), namely, 4 and 6, were experimentally obtained and comprehensively characterized. The two EMOFs both possess unique three-dimensional (3D) coordination structures. With a high crystal density of 2.184 g·cm-3, EMOF 4 exhibits outstandingly superior thermostability (onset: 290 °C; peak: 303 °C), while EMOF 6 features onset and peak decomposition temperatures of 220 and 230 °C. The calculated energetic parameters of 4 and 6 are as follows: detonation velocity: 8731 m·s-1 and 8294 m·s-1; detonation pressure: 26.5 and 26.4 GPa. Compared to EMOF 6, EMOF 4 features high energy, excellent thermostability, and low mechanical sensitivities, which should be partly attributed to more plentiful coordination interactions. More coordination bonds are conducive to strengthening the EMOF framework, which needs much more energy to collapse, thereby maintaining higher thermal stability. The above favorable characteristics not only indicate EMOF 4 has a promising future in applications as a thermostable explosive but also provide an effective and feasible strategy for developing novel heat-resistant energetic materials via reinforced frame structures of EMOFs.

Design and Synthesis of Energetic Melt-Castable Materials by Substituent-Specific Modification.

With the increase in the demand for high-performance composite explosives, the search for advanced energetic melt-castable compounds has attracted increasing attention in the field of energetic materials. Herein, two new energetic materials with nitromethyl and azidomethyl substituents (1-(nitromethyl)-3,4-dinitro-1H-pyrazole (NMDNP) and 1-(azidomethyl)-3,4-dinitro-1H-pyrazole (AMDNP) were prepared by the substituent modification of a potential melt-castable molecule ((3,4-dinitro-1H-pyrazol-1-yl) methyl nitrate, MC-4), respectively. NMDNP exhibited a suitable melting point (90 °C), good thermal stability (Td : 185 °C) and excellent detonation performance (8484 m s-1 ) and impact sensitivity (25 J), thereby demonstrating promise as an energetic melt-castable material. Simultaneously, compared with the nitrato-methyl and azidomethyl substituents, the nitromethyl substituent exhibited greater advantages in regulating performance.

Multiple Hydrogen-Bond Modification of [1,2,5]Oxadiazolo[3,4-b]pyridine 1-Oxide Framework Enables Access to Low-Sensitivity High-Energy Materials.

In this work, a fused-ring [1,2,5]oxadiazolo[3,4-b]pyridine 1-oxide framework with multiple modifiable sites was utilized to develop novel energetic materials with multiple hydrogen bonds. The prepared materials were characterized, and their energetic properties were extensively investigated. Among those studied, compound 3 exhibited high densities of 1.925 g cm-3 at 295 K and 1.964 g cm-3 at 170 K, with high detonation performances (Dv: 8793 m s-1 and P: 32.8 GPa), low sensitivities (IS: 20 J, FS: 288 N), and good thermal stability (Td: 223 °C). N-Oxide compound 4 had higher-energy explosive (Dv: 8854 m s-1 and P: 34.4 GPa) and low sensitivities (IS: 15 J and FS: 240 N). Compound 7 with a high enthalpy group (tetrazole) was determined as a high-energy explosive (Dv: 8851 m s-1, P: 32.4 GPa). Notably, the detonation properties of compounds 3, 4, and 7 were similar to high-energy explosive RDX (Dv: 8801 m s-1 and P: 33.6 GPa). The results indicated that compounds 3 and 4 were potential low-sensitivity high-energy materials.

Hunting for Energetic Complexes as Hypergolic Promoters for Green Propellants Using Hydrogen Peroxide as Oxidizer.

The development of hypergolic materials has aroused great interest due to their important applications in aerospace technology. In this work, six new energetic complexes were prepared and comprehensively characterized. All energetic complexes had isostructural characteristics, which made them ideal candidates for studying their structure-performance relationships. These energetic complexes had good thermal stabilities and excellent specific impulses. The vacuum-specific impulses were in the range 264.0-271.9 s, which was greater than most reported solid hypergolic materials. Moreover, the hypergolic performance of these compounds was examined by using 100% HNO3 as the oxidizer, and their catalytic performance in the hypergolic reaction of typical energetic ionic liquids and 90% H2O2 was comprehensively studied. All compounds displayed excellent hypergolic performance with the shortest ignition delay time of 4 ms. The examined copper-containing energetic complexes displayed excellent catalytic activities for the hypergolic reaction between energetic ionic liquids and 90% H2O2. The shortest ignition delay time of the examined hypergolic reactions was 31 ms. The suitable physicochemical properties, excellent energetic properties, and high catalytic activity of the hypergolic reactions have demonstrated the great potential of these energetic complexes as promoters for the development of green hypergolic bipropellants.

Energetic isomers of bridged oxadiazole nitramines: the effect of asymmetric heterocyclics on stability and energetic properties.

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.

Self-Assembly of Nitrogen-Rich Heterocyclic Compounds with Oxidants for the Development of High-Energy Materials.

The development of energetic materials with high energy and low sensitivity has attracted immense interests due to their widespread applications in aerospace technology and national defense. In this work, a promising self-assembly strategy was developed to prepare three high-energy materials (1-3) through the introduction of oxidant molecules into the crystal voids of the parent materials. The structures of these new materials were comprehensively examined by infrared spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and single-crystal X-ray diffraction. In these materials, three unique layer structures with hcb, sql, and interrupted sql topologies were observed, which were formed by the fused-ring-based energetic components. Windows with hexagonal, square, and rectangular structures were observed within these layer structures, which were occupied by H2O2, NO3-, and ClO4-, respectively. Oxidant molecules interacted with parent molecules via hydrogen bonds to form crystal structures of these materials. Moreover, the energetic property of these materials was estimated by computing methods. The calculation results revealed that these self-assembly materials exhibit excellent energetic properties. The highest energetic performance was observed for compound 3. The detonation velocity, detonation pressure, and specific impulse values were up to 9339 m·s-1, 42.5 GPa, and 308 s, respectively, which were greater than those of HMX. Furthermore, these materials exhibited good sensitivity, which was closely related to their unique crystal structures. The high performance of these materials indicated that the self-assembly strategy should be a promising method for the development of novel energetic materials.

Structural Analysis and Controllable Fabrication of Two Pentazolate-Based 3D Topological Networks.

Two novel sodium-pentazolate frameworks (namely, MPF-3 and MPF-4) were achieved by adding simple additives. MPF-3 exhibits an aesthetic three-dimensional (3D) framework with the zeolitic MTN topology, featuring Na28N80 and Na20N60 nanocages. In MPF-4, two left-handed helical chains construct enclosed homochiral channels filled with dimethyl sulfone molecules, which constitute a zeolite-like UNJ topology. Importantly, the preparation of these two compounds provides an effective experimental means to explore the unique symmetrical structure and multiple coordination modes of pentazolium anion and demonstrates that it is possible to regulate the crystal structure through appropriate additives.

Identification and expression analysis of the WRKY gene family in Isatis indigotica.

The WRKY proteins, which represent one of the largest families of transcriptional regulators in plants, play pivotal roles in regulating multiple processes of growth and development, particularly in diverse stress responses. Isatis indigotica is widely used in Traditional Chinese Medicine and is famous for its use as a dye for the color indigo. However, reports of the WRKY gene family in I. indigotica are limited. In this study, 64 IiWRKY genes encoding proteins with the complete WRKY domain were identified from genome of I. indigotica. Based on their structure and phylogenetic relationships of this gene family in I. indigotica, the IiWRKY genes were classified into three groups: Group I (n = 13), Group II (n = 35) and Group III (n = 16). Sequence alignment revealed that IiWRKY proteins harbored two variants, WRKYRQK and WRKYGKK, of the highly conserved WRKYGQK motif. The number of exons in IiWRKY genes varied from two to 14, with most of IiWRKY genes containing three exons. Investigation of gene duplication demonstrated that 10 and 14 IiWRKY genes were incorporated in tandem and segmental duplication events, respectively. Finally, the expression profiles derived from transcriptome data and quantitative real-time PCR analysis showed distinct expression patterns of these IiWRKY gene in five different organs or in response to four abiotic stresses. Taken together, our results will contribute to functional analysis of IiWRKY genes, and also provide a basis for further clarification of the molecular mechanism of stress responses in this important herb.

Molecular and Crystal Features of Thermostable Energetic Materials: Guidelines for Architecture of "Bridged" Compounds.

Extensive density functional theory (DFT) calculation and data analysis on molecular and crystal level features of 60 reported energetic materials (EMs) allowed us to define key descriptors that are characteristics of these compounds' thermostability. We see these descriptors as reminiscent of "Lipinski's rule of 5", which revolutionized the design of new orally active pharmaceutical molecules. The proposed descriptors for thermostable EMs are of a type of molecular design, location and type of the weakest bond in the energetic molecule, as well as specific ranges of oxygen balance, crystal packing coefficient, Hirshfeld surface hydrogen bonding, and crystal lattice energy. On this basis, we designed three new thermostable EMs containing bridged, 3,5-dinitropyrazole moieties, HL3, HL7, and HL9, which were synthesized, characterized, and evaluated in small-scale field detonation experiments. The best overall performing compound HL7 exhibited an onset decomposition temperature of 341 °C and has a density of 1.865 g cm-3, and the calculated velocity of detonation and maximum detonation pressure were 8517 m s-1 and 30.6 GPa, respectively. Considering HL7's impressive safety parameters [impact sensitivity (IS) = 22 J; friction sensitivity (FS) = 352; and electrostatic discharge sensitivity (ESD) = 1.05 J] and the results of small-scale field detonation experiments, the proposed guidelines should further promote the rational design of novel thermostable EMs, suitable for deep well drilling, space exploration, and other high-value defense and civil applications.

[Effects of drought stress on glandular trichomes,stomatal density and volatile exudates of Schizonepeta tenuifolia].

In this research,we explored the effect of three groups of water treatments,including severe drought(the corresponding water content of cultivated substrate 5%-10%),moderate drought(45%-50%) and control(85%-90%),and different drought stress time(15,30,45 d) on the glandular trichome density(TD),stomatal density(SD) and volatile exudates of Schizonepeta tenuifolia.The results showed that there were two kinds of glandular trichomes on the surface of S. tenuifolia leaves: peltate and capitate glandular trichomes. The density of capitate glandular trichomes(CTD) was higher than that of peltate glandular trichomes(PTD). Both CTD and PTD on the abaxial surface of leaf were higher than those on the adaxial surface. Under severe drought stress,the CTD and SD were higher than the other two treatments. Under the same stress time,the biomass and leaf surface area of S. tenuifolia decreased with the deepening of stress degree. As the stress time prolonged,the surface area of leaves and biomass gradually increased,and the TD and SD decreased. The most abundant compound in volatile exudates of S. tenuifolia was pulegone. Under drought stress,the relative content of pulegone decreased,and the relative content of other monoterpenoids such as D-limonene and menthone increased. The n-hexadeconic acid and 2-methyl-1-hexadecanol were detected only at the stress of 15 d,while menthone was detected at the stress of 30 d and45 d. Drought stress affected the leaf growth and secondary metabolism of S. tenuifolia.

Combination of gem-dinitromethyl functionality and a 5-amino-1,3,4-oxadiazole framework for zwitterionic energetic materials.

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.

Synthesis of Thermally Stable and Insensitive Energetic Materials by Incorporating the Tetrazole Functionality into a Fused-Ring 3,6-Dinitropyrazolo-[4,3-c]Pyrazole Framework.

A series of fused-ring energetic materials, i.e., 3,6-dinitro-1,4-di(1H-tetrazol-5-yl)-pyrazolo[4,3-c]pyrazole (DNTPP, compound 2) and its ionic derivatives (compounds 3-8), were designed and synthesized in this study. The molecular structures of compounds 2, 3, 6, 7·2H2O, and 8 were confirmed using single-crystal X-ray diffraction. Their physicochemical and energetic properties, such as density, thermal stability, heat of formation, sensitivity, and detonation properties (e.g., detonation velocity and detonation pressure), were also evaluated. The results indicate that DNTPP and most of its ionic derivatives are extremely thermally stable and insensitive toward mechanical stimuli. In particular, the thermal decomposition temperature of compound 3 is up to 329 °C, while compounds 7 and 8 are very insensitive (impact sensitivity: >20 J; friction sensitivity: >360 N). Compounds 2, 3, and 6 possess good comprehensive properties, including excellent thermal stability, remarkable low sensitivities, and favorable detonation performance. These features show that DNTPP and its ionic derivatives have considerable promise as thermally stable and insensitive energetic materials.

Fabrication of protonated g-C3N4 nanosheets as promising proton conductive 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.

[Response of growth and photosynthetic characteristics of Polygonatum cyrtonema to shading conditions].

The purpose of this experiment was to study the effects of different shading conditions on the growth,physiological characteristics and biomass allocation of Polygonatum cyrtonema,which offered a theoretical basis for its cultivation.Different light environments(100%,80%,60% and 35% light transmittance) were simulated with shading treatments.Growth and photosynthetic indexes of P.cyrtonema were measured and the variances were analyzed.The results show that shading decreased superoxide anion radical(O-·2)production rate and hydrogen peroxide(H_2O_2) accumulation,kept the activity of SOD,POD and CAT enzyme at a high level.Furthermore,The content of chlorophyll a and chlorophyll b,net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),maximal photochemical efficiency of photosystem Ⅱ(Fv/Fm),photochemical quenching index(q P) and effective quantum yield of photosystem II(ΦPSⅡ) of P.cyrtonema were increased while the intercellular CO2 concentration(Ci),Foand NPQ were decreased by shading.Shading is beneficial to P.cyrtonema growth,can increase the total biomass P.cyrtonema.The allocation proportion of biomass on the aerial portion of P.cyrtonema increased but underground parts decreased with increasing shading conditions.In this study,P.cyrtonema can grow well in shading conditions,shading is beneficial to the formation of the yield and quality of the rhizomes of P.cyrtonema,especially in 65% light transmittance.

Revisiting the reactive chemistry of FOX-7: cyclization of FOX-7 affords the fused-ring polynitro compounds.

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.

[Changes of ion absorption, distribution and essential oil components of flowering Schizonepeta tenuifolia under salt stress].

In this paper, a pot experiment using quartz sands was conducted to study the effects of different concentrations of NaCl (0, 25, 50, 75, 100 mmol·L⁻¹) on the ion absorption, distribution and essential oil components of flowering Schizonepeta tenuifolia. The results showed that as NaCl concentration increased, Na⁺ content of root, stem, leaf and flower increased significantly, and that of the aerial parts was in a higher level than in the root. Regarding the K⁺ content, it decreased in the root but increased in stem, leaf and flower. Some changes were detected in the Ca²âº content, but not significant on the whole. The value of K⁺/Na⁺ and Ca²âº/Na⁺ reduced as a result of increasing NaCl concentrations. The content of essential oil increased under medium salt treatment (50 mmol·L⁻¹ NaCl). However, the synthesis and accumulation of essential oil was inhibited by the serious salt treatment (100 mmol·L⁻¹ NaCl). Over 98% of the essential oil components were terpenes, in which pulegone and menthone were the most two abundant compounds. Varieties of essential oil components did not change significantly under salt stress but their relative proportions did. The transformation of pulegone to menthone was enhanced and the value of pulegone/menthone based on their relative contents decreased with NaCl concentration increasing. Consequently, menthone ranked the most abundant compound by replacing pulegone. Relative content of D-limonene increased under medium and serious salt stress, and that of ß-caryophyllene only increased under mild treatments. So our research could provide references for the standard cultivation on saline soil of S. tenuifolia.

[Effects of N and Zn interaction on growth, yield and active components of Agastache rugosa].

The study is aimed to explore the effect of combination use of nitrogen(N) and zinc(Zn) fertilizers on the growth, yield and the effective components of Agastache rugosa. A. rugosa was grown under two N application rate (120, 300 kg·hm⁻²) and five Zn levels (0, 20, 50, 100，150 kg·hm⁻²) under field condition. The effect of the treatments on the physiological indicators, distribution of nitrogen and zinc and volatile oil components of A. rugosa were studied. The results showed that the combination use of N and Zn could significantly affect the growth and development, yield and volatile oil components of A. rugosa. Under the test conditions, the highest yield of Agastaches Herba was obtained when 50 kg·hm⁻² of Zn fertilizer was applied with high N application rate of 300 kg·hm⁻². Under the same N application rate, the increase of Zn production was positively correlated with the amount of Zn application in a certain concentration range, but excessive Zn application led to the decrease of yield. With the increase of N application level, the content of Zn also significantly increased. The combination use of N and Zn increased the yield of Agastaches Herba. High level of N application was beneficial to the absorption and accumulation of N and Zn of A. rugosa. Zn fertilizer could also promote the absorption and accumulation of N of A. rugosa. The interaction between N and Zn had significant influence on the main chemical constituents of the volatile oil of A. rugosa. Among the volatile oil chemical constituents of A. rugosa the content of pulegone (34.56%-53.91%) and piperonyl methyl ether (18.86%-42.27%) were much higher. Under the same N application rate, different Zn application rates also had significant effects on the main chemical components of volatile oil.

A simple and versatile strategy for taming FOX-7.

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.

Ionothermal Synthesis of Open-Framework Metal Phosphates Using a Multifunctional Ionic Liquid.

Two crystalline metal phosphates (metal = Be and Al) were prepared under ionothermal conditions using a multifunctional ionic liquid as a solvent, a structure-directing agent, and a phosphorus source. The beryllium phosphate has a three-dimensional structure with intersecting 24-membered ring (24 MR) channels. The aluminum phosphate has a two-dimensional structure containing 8 MR windows. It displays exceptional hydrothermal stability and shows a high proton conductivity on the order of 10-3 S cm-1 at 25 °C under high humidity conditions.

Accelerating the discovery of insensitive high-energy-density materials by a materials genome approach.

Finding new high-energy-density materials with desired properties has been intensely-pursued in recent decades. However, the contradictory relationship between high energy and low mechanical sensitivity makes the innovation of insensitive high-energy-density materials an enormous challenge. Here, we show how a materials genome approach can be used to accelerate the discovery of new insensitive high-energy explosives by identification of "genetic" features, rapid molecular design, and screening, as well as experimental synthesis of a target molecule, 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide. This as-synthesized energetic compound exhibits a graphite-like layered crystal structure with a high measured density of 1.95 g cm-3, high thermal decomposition temperature of 284 °C, high detonation velocity of 9169 m s-1, and extremely low mechanical sensitivities (impact sensitivity, >60 J and friction sensitivity, >360 N). Besides the considered system of six-member aromatic and hetero-aromatic rings, this materials genome approach can also be applicable to the development of new high-performing energetic materials.