High-Energy Metal–Organic Frameworks with a Dicyanamide Linker for Hypergolic Fuels

Yuan W., Zhang L., Tao G., Wang S., Wang Y., Zhu Q., Zhang G., Zhang Z., Xue Y., Qin S., He L., Shreeve J.M.

Propellant materials genome offers a new approach to the design of high-performance hypergolic propellants.

Zhang Y., Nie J., Cao J., Liu Y., Chen Y., Nie G., Pan L., Zhang X., Zou J.

Flammable liquid fuels are potential candidates to replace hydrazine derivatives as hypergolic fuel and to promote ignition and combustion of high-density fuels as additives. Here 1,4-dicyclopropylbuta-1,3-diyne (DCPB) with high density (0.932 g/mL) and net heating value (42.47 MJ/kg) was synthesized by simple copper-catalyzed alkyne coupling reaction. As hypergolic fuel, DCPB has a short ignition delay time of 19 ± 0.11 ms when contacting with fuming nitric acid. The calculated enthalpy of formation (ΔfH) of DCPB and specific impulse (Isp) using O2(L), N2O4(L) and HNO3(L) as oxidants are 499.2 kJ/mol, 394.7 s, 355.4 s and 334.7 s, respectively, much higher than that of hydrazine (50.9 kJ/mol, 379.0 s, 350.2 s and 333.5 s). The high Isp and short ignition delay time supported DCPB can be used as hypergolic fuel. As ignition additive, high temperature droplet plate and shock tube tests confirm that DCPB is effective to reduce the ignition delay time and lower the apparent ignition activation energy of high-density fuels like JP-10. Therefore, DCPB can be used as potential hypergolic fuel and ignition additive of high-density fuel.

Zhang X., Xue Z., Wang Z., Chen S., Yang Z., Yan Q.

In this paper, the widely used energetic material RDX had been modified with 2D high nitrogen polymer (TAGP). Various hybrid RDX crystals (qy-RDX) with higher detonation velocity and better thermostability had been obtained as a result of strong intermolecular interactions between TAGP and RDX molecules. The performance of the qy-RDX had been characterized to clarify the inherent mechanisms. It shows that the⊿Hf of qy-RDX could be largely changed in the range of 23.4 kJ kg-1 to 1343.6 kJ kg-1, whereas the density varies only from 1.81 g cm-3 to 1.86 g cm-3. The resulted detonation velocities are in the range of 8725.5 m·s-1 to 9251.8 m·s-1, depending on the content and state of the TAGP dopant. The sensitivity of the resulted qy-RDX is much better than pristine RDX due to improved crystal quality as well as higher concentration of hydrogen bonds. The impact energy is improved from 8.5 J (RDX) to 22 J (qy-RDX-1), whereas the friction sensitivity improves form 130 N to over 360 N for the same case. The Ea for thermal decomposition of qy-RDX-1has reduced from 147.8 kJ mol-1 (RDX) to (124.5 kJ mol-1), since TAGP dopant could be considered as active catalytic sites after melting of RDX.

Sun C., Tang S.

In this paper, four kinds of guanidinium dicyanamide-based energetic salts were prepared and investigated as energetic additives to hypergolic ionic liquid 1-ethyl-3-methyl imidazolium dicyanamide ...

Zou Z., Wang J., Pan H., Li J., Guo K., Zhao Y., Xu C.

Metal–organic frameworks (MOFs) have been considered as versatile materials for applications in energy fields.

Wang Q., Wang J., Wang S., Wang Z., Cao M., He C., Yang J., Zang S., Mak T.C.

Atomically precise o-carboranealkynyl-protected clusters [Ag14(C4B10H11)12(CH3CN)2]·2NO3 (CBA-Ag) and [Cu6Ag8(C4B10H11)12Cl]NO3 (CBA-CuAg) have been found to exhibit hypergolic activity, such that they are capable of spontaneous ignition and combustion upon contact with the white fuming nitric acid oxidizer. In particular, CBA-CuAg has a short ignition delay time of 15 ms, whereas the o-carboranealkynyl ligand is hypergolically inert. Systematic investigation revealed that the metal cluster core catalyzed the hypergolic behavior of inert o-carboranealkynyl ligand, and Cu doping further accelerated combustion catalysis. This work provides a new prospective in the rational design of novel metal cluster-based hypergolic fuels for propellant application.

Zhong Y., Li Z., Xu Y., Lei G., Zhang J., Zhang T.

Four new coordination compounds were synthesized by the reactions of transition-metal inorganic salts with 1-ethylimidazole (EIMI) and sodium dicyanamide (NaDCA), and were characterized by elementa...

Bhosale V.K., Jeong J., Choi J., Churchill D.G., Lee Y., Kwon S.

The exploration of environmentally friendly hypergolic combinations of ionic liquid fuels and hydrogen peroxide as an oxidizer offers opportunities to replace commonly used conventional toxic, corrosive and carcinogenic hydrazine-based liquid hypergolic combinations. Various research opportunities await regarding the detailed investigations of green hypergolic ionic liquids (HILs) with rocket grade hydrogen peroxide (RGHP, >85% H2O2). In this work, the combustion of HILs 1-ethyl-3-methyl imidazolium cyanoborohydride ([EMIM][BH3CN]) and 1-allyl-3-ethyl imidazolium cyanoborohydride ([AEIM][BH3CN]), and HIL-additive mixtures with 95% H2O2 has been investigated. A new additive, 1,3-dimethyl imidazolium copper iodide ([diMIM]n[Cu2I3]n) was synthesized successfully; a structural investigation was performed through the use of single-crystal x-ray diffraction analysis through which a crystal density of 3.22 g/cm3 was revealed. The physicochemical properties (density, viscosity, and decomposition temperature) as well as performance parameters (ignition delay and specific impulse) of 2 to 15 wt% of [diMIM]n[Cu2I3]n in [EMIM][BH3CN] were determined. A 15 wt% of [diMIM]n[Cu2I3]n exhibited ignition delay time (IDT) values of 13 and 29 ms under fuel-rich and oxidizer-rich conditions, respectively; these IDT values are 100 times lower than those for [EMIM][BH3CN]. Interestingly, [diMIM]n[Cu2I3]n-[EMIM][BH3CN] combinations revealed high density (>0.98 g/cm3), good thermal (>200 °C) and chemical stability, and 5.6–6.0% higher density specific impulse than those found for unsymmetrical dimethyl hydrazine. The additive-promoted hypergolic combustion of HIL with RGHP opens a new avenue to the replacement of conventional toxic hypergolic combinations.

Wurzenberger M.H., Lechner J.T., Stierstorfer J.

Following the useful concept of energetic coordination compounds (ECC), copper(II) dicyanamide was used as a building block for the synthesis of eight new complexes. As ligands, six different N-substituted tetrazoles were applied, leading to the formation of high-nitrogen containing complexes. The obtained compounds were characterized in detail by single crystal as well as powder XRD, IR, EA, DTA, and TGA. In addition, the sensitivities towards impact and friction were determined with BAM standard techniques as well as the sensitivity towards electrostatic discharges. All compounds show moderate sensitivities (IS>6, FS>80 N) and energetic properties but differ in their polymeric structures forming polymeric chains or layers up to 3D networks.

Huang M., Wang Z., Jin J.

Since the discovery of graphene and its derivatives, the development and application of two-dimensional (2D) materials have attracted enormous attention. 2D microporous materials, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), graphitic carbon nitride (g-C3 N4 ) and so on, hold great potential to be used in gas separation membranes because of their high aspect ratio and homogeneously distributed nanometer pores, which are beneficial for improving gas permeability and selectivity. This review briefly summarizes the recent design and fabrication of 2D microporous materials, as well as their applications in mixed matrix membranes (MMMs) for gas separation. The enhanced separation performances of the membranes and their long-term stability are also introduced. Challenges and the latest development of newly synthesized 2D microporous materials are finally discussed to foresee the potential opportunities for 2D microporous material-based MMMs.

Thomas A.E., Chambreau S.D., Redeker N.D., Esparza A.A., Shafirovich E., Ribbeck T., Sprenger J.A., Finze M., Vaghjiani G.L.

In this study, in situ infrared spectroscopy techniques and thermogravimetric analysis coupled with mass spectrometry (TGA-MS) are employed to characterize the reactivity of the ionic liquid, 1-butyl-3-methylimidazolium dicyanoborohydride (BMIM+DCBH-), in comparison to the well-characterized 1-butyl-3-methylimidazolium dicyanamide (BMIM+DCA-) ionic liquid. TGA measurements determined the enthalpy of vaporization (ΔHvap) to be 112.7 ± 12.3 kJ/mol at 298 K. A rapid scan Fourier transform infrared spectrometer was used to obtain vibrational information useful in tracking the appearance and disappearance of species in the hypergolic reactions of BMIM+DCBH- and BMIM+DCA- with white fuming nitric acid (WFNA) and in the thermal decomposition of these energetic ionic liquids. Attenuated total reflectance measurements recorded the infrared spectra of the reactant sample (BMIM+DCBH-) and the liquid reaction products after reacting with WFNA. Computational chemistry efforts, aided by the experimental results, were used to propose key reaction pathways leading to the hypergolic ignition of BMIM+DCBH- + WFNA. Experimental results indicate that the hypergolic reaction of BMIM+DCBH- with WFNA generates both common and unique intermediates as compared to previous BMIM+DCA- + WFNA investigations: nitrous oxide was generated during both hypergolic reactions indicating that it may play a crucial role in the hypergolic ignition process, NO2 was generated in significantly higher concentrations for BMIM+DCBH- than for BMIM+DCA-, CO2 was only generated for BMIM+DCA-, and HCN was only generated during thermal decomposition and hypergolic ignition of BMIM+DCBH-.

Bhosale V.K., Karnik S., Kulkarni P.S.

Boron based compounds have been looked upon as possible replacements to conventional toxic hypergolic fuels in propellant system. In an attempt to add to the pool of boron based hypergols, a series of new amine borane/ cyanoborane zwitterionic compounds were developed. Their hypergolic reactivity, performance parameters and physico-chemical properties were examined, in detail. The unsymmetrical dimethyl hydrazine (UDMH) based zwitterions, UDMH-borane and UDMH-bisborane displayed strikingly lower ignition delay times of 2.2 and 2 ms, respectively and high specific impulse 241 and 245 s, respectively. The pyridinium-cyanoborohydride exhibited high heat of formation (146 kJ/mol) than UDMH. While all the developed compounds exhibited higher density than the UDMH. Chemical stability of UDMH-borane was investigated at different environmental conditions; it was found to be stable for longer duration. Low ignition delay, good thermal and chemical stability, positive heat of formation, high specific impulse, ease of synthesis, and commercially available starting materials are the promising features of these compounds which make them attractive prospects in revolutionizing the area of green hypergolic fuel in liquid as well as hybrid rocket propulsion.

Kaur H., Sundriyal S., Pachauri V., Ingebrandt S., Kim K., Sharma A.L., Deep A.

Metal-Organic Frameworks (MOFs) are hybrid organic-inorganic materials with enhanced electronic and optical functionalities that can be tailored by the judicious selection of the building units or their combinations. A large-scale diversity of metal-ligand combinations, along with the ability to form composites, have allowed MOFs to realize enhanced luminescence functionality with applicability in the avenues of solid-state lighting, luminescence-based sensors, and organic light emitting diodes (OLEDs). Because of their enhanced fluorescence lifetimes, high quantum efficiencies, and large-scale tunability, the luminescent MOFs and their composites hold great promise for the OLED industry with enhanced potential to resolve low efficiency issues. The present article presents a comprehensive review of emerging applications for luminescent MOFs and their composites in various OLED applications, with a focus on key attributes like quantum efficiencies, emission lifetimes, tunability, Commission internationale de l'eclairage (CIE) color coordinates, etc. At last, the prospects of luminescent MOFs have been addressed with respect to their future roles and applications in the OLED industry.

Titi H.M., Arhangelskis M., Rachiero G.P., Friščić T., Rogers R.D.

It′s not rocket science: Co-crystallization of a hypergolic decaborane building block designed for hydrogen bonding with energetic but not hypergolic or explosive fuel molecules enables the simple and rapid synthesis of new hypergolic materials with tunable energetic properties and ultrashort ignition delays down to 1 ms.

Titi H.M., Marrett J.M., Dayaker G., Arhangelskis M., Mottillo C., Morris A.J., Rachiero G.P., Friščić T., Rogers R.D.

Metal-organic frameworks offer a design for new, clean, and tunable hypergolic fuels with ultrashort ignition delays.

Weng J., Li L., Wang J., Yang Y., Jiang P., Zhang N., Cui M., Xu J., Guo G.

Wang J., Lv R., Wang H., Zhang Q., Huang S., Wang K.

Wang J., Zhang Q., Wang H., Sun N., Wang K.

Świtlicka A.

In recent decades, the chemistry of transition metal coordination compounds has undergone continuous development at both scientific and application levels. The diversity of metal(II) complexes, along with their structural features and physicochemical properties, makes them attractive for a wide range of applications. The dicyanamide ion (N(CN)2) has the ability to form various transition metal compounds characterized by different architectures and topologies. The interaction of π-electrons from the nitrile groups with the π-system of the central nitrogen may enable electron delocalization, potentially facilitating electron transfer between the metal centers through the bridging dicyanamide (dca) ligand. This review focuses on dca–Co(II) compounds and, after a brief introduction, the structural aspects and magnetic properties are analyzed in detail.

Xie H., Yang W., Lin F., Wu B., Zhang Z., Han S., Liu W., Zheng F., Xu J.

The design and development of azide-based energetic metal–organic frameworks (EMOFs) with high energy and reliable stabilities for energetic materials still remains significant challenges. Herein, we utilized two rigid triazole-based polydentate ligands to design and synthesize two stable azide-based EMOFs [Cd(N3)(TRZ)]n 1 (HTRZ = 1,2,4-triazole) and [Cd(N3)(ATRT)(H2O)]n 2 (HATRT = 5-amino-3-(4H-1,2,4-triazol-4-yl)-1H-1,2,4-triazole). Structural analysis reveals that 1 displays a unique 3D inserted 3D framework, and 2 presents a rigid 2D network with strong π-π packing interactions. Compounds 1 and 2 feature rarely insensitive to mechanical stimulation and exhibit excellent thermal stabilities reaching up to 371 and 366 °C, respectively. The calculated heats of detonation (ΔHdet) of 2 is 5.315 kJ·g−1, which is much higher than that of the traditional explosive 2,4,6-trinitrotoluene (TNT, ΔHdet = 3.72 kJ·g−1). The experimental results and theoretical calculations demonstrate that the specific structure of 1 and the rigid 2D network of 2 produce high mechanical strength. This study not only provides two azide-based EMOFs with reliable stabilities as potential replacements for traditional energetic materials, but also illustrates a new insight into building stable structural models of azide-based EMOFs.

Ma G., Jiang Y., Qu Q., Fang C., Li H., Ding J., Wan H., Guan G.

Cheng Q., Yao Y., Dou P., Liu L., Cao Y., Zhang Y.

Zero-dimensional Cu-MOFs 3–4 could make the N(CN)2− IL and H2O2 from non-hypergolic to self-ignition.

Huang J., Ji A., Wang Z., Wang Q., Zang S.

AbstractHypergolic propellants rely on fuel and oxidizer that spontaneously ignite upon contact, which fulfill a wide variety of mission roles in launch vehicles and spacecraft. Energy‐rich carboranes are promising hypergolic fuels, but triggering their energy release is quite difficult because of their ultrastable aromatic cage structure. To steer the development of carborane‐based high‐performance hypergolic material, carboranylthiolated compounds integrated with atomically precise copper clusters are presented, yielding two distinct isomers, Cu14B‐S and Cu14C‐S, both possessing similar ligands and core structures. With the migration of thiolate groups from carbon atoms to boron atoms, the ignition delay (ID) time shortened from 6870 to 3 ms when contacted with environmentally benign oxidizer high‐test peroxide (HTP, with a H2O2 concentration of 90%). The extraordinarily short ignition ID time of Cu14B‐S is ranking among the best of HTP‐active hypergolic materials. The experimental and theoretical findings reveal that benefitting from the migration of thiolate groups, Cu14B‐S, characterized by an electron‐rich metal kernel, displays enhanced reducibility and superior charge transfer efficiency. This results in exceptional activation rates with HTP, consequently inducing carborane combustion and the simultaneous release of energy. This fundamental investigation shed light on the development of advanced green hypergolic propulsion systems.

Sajjadi M., Nasrollahzadeh M., Ghafuri H., Pombeiro A.J., Hazra S.

N-Donor tetrazole (TZ) derivatives possess physicochemical features, such as good thermostability/chemical stability, abundant coordination modes, high dipole moment, high formation enthalpy, basicity and acidity, as well as fluorescence/luminescent and magnetic behaviors, which make them widely utilized in both academic and industrial fields, namely in medicinal/biological chemistry, coordination chemistry and materials science. This review shows the progress in the synthesis, structures, features, catalytic applications and activities of copper coordination compounds derived from TZ derivatives, including coordination polymers (CPs) as versatile functional metal–organic materials.

Wang T., Bu S., Wang K., Zhang L., Yi Z., Zhu S., Zhang J.

Based on the theory of crystallization, a solvent-free solid-liquid phase crystallization method called solid-melt crystallization was designed to prepare energetic coordination polymers. Two target compounds [Cu(NPyz)4NO3]·NO3 (ECPs-1) and Cu(NPyz)4(ClO4)2 (ECCs-2) were prepared through programmed heating and cooling by using 4-nitropyrazole (NPyz), (Cu(NO3)2·5H2O and Cu(ClO4)2·5H2O as raw materials. In addition, crystallization pre-experiments and annealing experiments also verified the feasibility of the method. Their structures were confirmed by IR, elemental analysis, single-crystal X-ray diffraction and powder X-ray diffraction. The physicochemical properties and sensitivity test results showed that ECCs-2 has better thermal stability (Td = 221 °C), while ECPs-1 is less sensitive to mechanical stimuli (IS = 12 J, FS = 240 N). Calculations based on EXPLO5 and the Kamlet-Jacobs equation showed that ECCs-2 has more considerable detonation performance (P = 25.2 GPa, D = 7.5 km/s). In comparison, the more intuitive results from the HN test, flame test, thermal resistance test and lead plate explosion test revealed that ECCs-2 has an “ acceptable” detonation performance. The laser detonation test also showed that ECCs-2 is a promising excellent laser detonation material (E = 408 mJ, P = 24 W, τ = 17 ms).

Hopa C., Yavuz A.B., Diken M.E., Gungor E.

From reaction mixture containing the same reagents, the two Cu(II) complexes, with dicyanamide (dca) bridges, [Cu(bpy)(dca)2]n (1) and [Cu(bpy)Cl(dca)]n·H2O (2) (bpy = 2,2′-bipyridine) were prepared. The complexes were characterized by elemental analysis, FTIR spectroscopy and X-ray single crystal techniques. In both complexes, the geometry of the Cu(II) atom is best described as a slightly distorted square pyramidal. A zigzag chain structure is formed in both structures by dca units serving as an end-to-end bridging ligand. In addition, studies on antibacterial activity of the compounds against Gram(+) (Staphylococcus aureus ATCC-6538) and Gram(–) (Escherichia coli ATTC-8739, Pseudomonas aeruginosa ATCC-27853 and Enterobacter aerogenes ATCC-13048) bacteria have been performed using disc-diffusion and microdilution broth techniques. Both complexes were found to be significantly more effective against Gram(–) bacteria E. Coli than against the other bacteria.

Bian H., Yan Y., Cui M., Song T., Guo X., Xu J., Zheng F., Guo G.

The design and development of advanced hypergolic metal-organic frameworks (HMOFs) for space exploration has attracted wide attention in recent years. However, enhancing the energy densities and elucidating the relationship between...

Wang Z., Fei L., Xia H., Jin Y., Zhang Q.

This study prepared a series of novel hypergolic fluids based on borohydride ionic liquids and organic superbase using an in situ synthetic method. In these hypergolic fluids, ionic liquids in 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) acted as triggers for the self-ignition of DBN and DBU upon contact with high-concentration hydrogen peroxide (H2O2). These hypergolic fluids had high densities (>1.000 ​g ​cm−3), low viscosities (as low as 34.03 ​cP), and acceptable ignition delay times (IDT). The ignition processes of the hypergolic fluids with 90% H2O2 as an oxidizer were first investigated in this study, and they differed from the previously reported ignition phenomena. Different from the case with white fuming acid (WFNA) as an oxidizer, the ignition processes of hypergolic fluids with 90% H2O2 as an oxidizer did not exhibit secondary rebound and splashing and formed a homogeneous mixed layer when the droplets were in contact with 90% H2O2. The different ignition processes significantly influenced the properties of hypergolic fluids. Compared with the hypergolic fluids with WFNA as an oxidizer, those with 90% H2O2 as an oxidizer showed a shorter IDT (IDTmin[90% H2O2]=28.3 ​ms, IDTmin[WFNA]=126 ​ms) and formed stable flames without secondary combustion. These results demonstrate that the in-situ synthesized fuels in this study hold great promise as green fuels in hypergolic propulsion systems.

Xu Y., Marrett J.M., Titi H.M., Darby J.P., Morris A.J., Friščić T., Arhangelskis M.

Luo L., Hao W., Jin B., Guo Z., Guo J., Liu Q., Deng H., Peng R.

The design and construction of high-dimension energetic metal organic frameworks (EMOFs) are a promising approach to balance stability and energetic performance. Herein, 3D EMOF [Pb 3 (BTT) 2 ] n (EMOF 1 , H 3 BTT = 4,5-bis(tetrazol-5-yl)-2H-1,2,3-triazole), which achieved integrating high density, excellent stability, and solvent-free, was successfully explored and accurately characterized. Single-crystal X-ray diffraction shows that it is orthorhombic and belongs to Pbca space group. The BTT 3− ligand features a 11-dentate coordination (total 11 nitrogen atoms), which compacts the structure of EMOF 1 , possesses high density (3.344 g·cm −3 ), and exhibits outstanding thermal stability ( T p = 377.8 °C) and mechanical sensitivity ( IS > 40 J, FS = 216 N). Its laser response process is tracked by laser initiation systems. The BTT 3− ligand features a 11-dentate coordination (total 11 nitrogen atoms), which compacts the structure of 3D solvent-free [Pb 3 (BTT) 2 ] n (EMOF 1 , H 3 BTT = 4,5-bis(tetrazol-5-yl)-2H-1,2,3-triazole), possesses high density (3.344 g·cm −3 ), and exhibits outstanding thermal stability ( T p = 377.8 °C) and mechanical sensitivity ( IS > 40 J, FS = 216 N). Its laser response process is tracked by laser initiation systems. • A dense 3D solvent-free EMOF 1 ([Pb 3 (BTT) 2 ] n ) achieved integrating high density and excellent stability. • It possesses high density (3.344 g·cm −3 ), and exhibits outstanding thermal stability ( T p = 377.8 °C) and mechanical sensitivity ( IS > 40 J, FS = 216 N). • The BTT 3− ligand features a novel 11-dentate coordination that all potential coordination sites are involved in coordination with metal centers. • Its moment of laser response was precisely and clearly captured by the high-speed camera.