Potassium 4,4′‐Bis(dinitromethyl)‐3,3′‐azofurazanate: A Highly Energetic 3D Metal–Organic Framework as a Promising Primary Explosive

Environmentally acceptable alternatives to toxic lead‐based primary explosives are becoming increasingly important for energetic materials. In this study, potassium 4,4′‐bis(dinitromethyl)‐3,3′‐azofurazanate, comprising two dinitromethyl groups and an azofurazan moiety, was synthesized and isolated as a new energetic 3D metal–organic framework (MOF). Several attractive properties, including a density of 2.039 g cm^?3, a decomposition temperature of 229 °C, a detonation velocity of 8138 m s^?1, a detonation pressure of 30.1 GPa, an impact sensitivity of 2 J, and friction sensitivity of 20 N make 4 a good candidate as a green primary explosive.     

Exchange of Coordinated Solvent During Crystallization of a Metal–Organic Framework Observed by In Situ High‐Energy X‐ray Diffraction

Using time‐resolved monochromatic high energy X‐ray diffraction, we present an in situ study of the solvothermal crystallisation of a new MOF [Yb₂(BDC)₃(DMF)₂]?H₂O (BDC=benzene‐1,4‐dicarboxylate and DMF=N,N‐dimethylformamide) under solvothermal conditions, from mixed water/DMF solvent. Analysis of high resolution powder patterns obtained reveals an evolution of lattice parameters and electron density during the crystallisation process and Rietveld analysis shows that this is due to a gradual topochemical replacement of coordinated solvent molecules. The water initially coordinated to Yb³⁺ is replaced by DMF as the reaction progresses.     

An Ultrahydrophobic Fluorous Metal–Organic Framework Derived Recyclable Composite as a Promising Platform to Tackle Marine Oil Spills

Derived from a strategically chosen hexafluorinated dicarboxylate linker aimed at the designed synthesis of a superhydrophobic metal–organic framework (MOF), the fluorine‐rich nanospace of a water‐stable MOF ( UHMOF‐100 ) exhibits excellent water‐repellent features. It registered the highest water contact angle (≈176°) in the MOF domain, marking the first example of an ultrahydrophobic MOF. Various experimental and theoretical studies reinforce its distinctive water‐repellent characteristics, and the conjugation of superoleophilicity and unparalleled hydrophobicity of a MOF material has been coherently exploited to achieve real‐time oil/water separation in recyclable membrane form, with significant absorption capacity performance. This is also the first report of an oil/water separating fluorinated ultrahydrophobic MOF‐based membrane material, with potential promise for tackling marine oil spillages.     

Three‐Dimensional Metal–Fullerene Frameworks

Hexakis‐substituted [60]fullerene adducts with icosahedral symmetry provide an unprecedented scaffold for the spatial arrangement of twelve functional groups with high geometric precision. This unique molecular symmetry identifies such polyfunctional organic building blocks as potential highly connective linkers for coordination polymer and metal–organic framework synthesis. Hereby, the linker exhibits a higher connectivity than the metal ions and with the main connectivity based on the ligand, this can create a new type of inversely cross‐linked framework. Two hexakis adducts bearing either twelve glycolic acid or 3‐hydroxypropionic acid side chains attached to its malonate units were incorporated as organic connectivity centers in the first fullerene‐containing three‐dimensional frameworks by coordination with Zn²⁺.     

Metal–Organic Frameworks (MOFs) as Safer,Structurally Reinforced Energetics

Second‐generation cobalt and zinc coordination architectures were obtained through efforts to stabilize extremely sensitive and energetic transition‐metal hydrazine perchlorate ionic polymers. Partial ligand substitution by the tridentate hydrazinecarboxylate anion afforded polymeric 2D‐sheet structures never before observed for energetic materials. Carefully balanced reaction conditions allowed the retention of the noncoordinating perchlorate anion in the presence of a strongly chelating hydrazinecarboxylate ligand. High‐quality X‐ray single‐crystal structure determination revealed that the metal coordination preferences lead to different structural motifs and energetic properties, despite the nearly isoformulaic nature of the two compounds. Energetic tests indicate highly decreased sensitivity and DFT calculations suggest a high explosive performance for these remarkable structures.     

Time‐Resolved In Situ X‐ray Diffraction Reveals Metal‐Dependent Metal–Organic Framework Formation

Versatility in metal substitution is one of the key aspects of metal‐organic framework (MOF) chemistry, allowing properties to be tuned in a rational way. As a result, it important to understand why MOF syntheses involving different metals arrive at or fail to produce the same topological outcome. Frequently, conditions are tuned by trial‐and‐error to make MOFs with different metal species. We ask: is it possible to adjust synthetic conditions in a systematic way in order to design routes to desired phases? We have used in situ X‐ray powder diffraction to study the solvothermal formation of isostructural M₂(bdc)₂dabco (M=Zn, Co, Ni) pillared‐paddlewheel MOFs in real time. The metal ion strongly influences both kinetics and intermediates observed, leading in some cases to multiphase reaction profiles of unprecedented complexity. The standard models used for MOF crystallization break down in these cases; we show that a simple kinetic model describes the data and provides important chemical insights on phase selection.     

In Situ Observation of Successive Crystallizations and Metastable Intermediates in the Formation of Metal–Organic Frameworks

Understanding the driving forces controlling crystallization is essential for the efficient synthesis and design of new materials, particularly metal–organic frameworks (MOFs), where mild solvothermal synthesis often allows access to various phases from the same reagents. Using high‐energy in situ synchrotron X‐ray powder diffraction, we monitor the crystallization of lithium tartrate MOFs, observing the successive crystallization and dissolution of three competing phases in one reaction. By determining rate constants and activation energies, we fully quantify the reaction energy landscape, gaining important predictive power for the choice of reaction conditions. Different reaction rates are explained by the structural relationships between the products and the reactants; larger changes in conformation result in higher activation energies. The methods we demonstrate can easily be applied to other materials, opening the door to a greater understanding of crystallization in general.     

Synthesis and Investigation of Advanced Energetic Materials Based on Bispyrazolylmethanes

Herein we present the preparation and characterization of three new bispyrazolyl‐based energetic compounds with great potential as explosive materials. The reaction of sodium 4‐amino‐3,5‐dinitropyrazolate ( 5 ) with dimethyl iodide yielded bis(4‐amino‐3,5‐dinitropyrazolyl)methane ( 6 ), which is a secondary explosive with high heat resistance (T_dec=310 °C). The oxidation of this compound afforded bis(3,4,5‐trinitropyrazolyl)methane ( 7 ), which is a combined nitrogen‐ and oxygen‐rich secondary explosive with very high theoretical and estimated experimental detonation performance (V_det (theor)=9304 m s^?1 versus V_det(exp)=9910 m s^?1) in the range of that of CL‐20. Also, the thermal stability (T_dec=205 °C) and sensitivities of 7 are auspicious. The reaction of 6 with in situ generated nitrous acid yielded the primary explosive bis(4‐diazo‐5‐nitro‐3‐oxopyrazolyl)methane ( 8 ), which showed superior properties to those of currently used diazodinitrophenol (DDNP).     

Novel Highly Energetic Pyrazoles: N‐Trinitromethyl‐Substituted Nitropyrazoles

A new family of energetic compounds, nitropyrazoles bearing a trinitromethyl moiety at the nitrogen atom of the heterocycle, was designed. The desirable high‐energy dense oxidizers 3,4‐dinitro‐ and 3,5‐dinitro‐1‐(trinitromethyl)pyrazoles were synthesized in good yields by destructive nitration of the corresponding 1‐acetonylpyrazoles. All of the prepared compounds were fully characterized by multinuclear NMR and IR spectroscopy, as well as by elemental analysis. Single‐crystal X‐ray diffraction studies show remarkably high density. Impact sensitivity tests and thermal stability measurements were also performed. All of the pyrazoles possess positive calculated heats of formation and exhibit promising energetic performance that is the range of 1,3,5‐trinitroperhydro‐1,3,5‐triazine and pentaerythritol tetranitrate. The new pyrazoles exhibit positive oxygen balance and are promising candidates for new environmentally benign energetic materials.