Shiliang Huang

Structures, photoluminescence and photocatalytic properties of two novel metal–organic frameworks based on tetrazole derivatives

Two novel metal–organic frameworks, [Ag(ATZ)]n (1) (ATZ = 5-amino-tetrazole) and [Ag2(en)2(AT)]n (2) (en = ethylenediamine, AT = 5,5′-azotetrazolate), were prepared from corresponding Ag(I) salts and have been structurally characterized by elemental analysis, Fourier transform infrared spectroscopy and single crystal and powder X-ray diffraction. The structures of both compounds consist of 2-D three-connected layers that are linked by π–π overlap interactions between the tetrazolate fragments in neighbouring layers to form a 3-D supramolecular structure. The photoluminescence properties of solid samples of 1 and 2 at room temperature and their photocatalytic performance have also been reported and discussed. The results indicate that 1 seems to be a good candidate for a novel inorganic–organic photoactive material with high quantum yield. Moreover, compounds 1 and 2 represent the first examples of coordination polymers with a Ag ion that exhibit high, efficient photocatalytic abilities for dye degradation under UV light and show good stability toward photocatalysis.

Two nitrogen-rich Ni(II) coordination compounds based on 5,5′-azotetrazole: synthesis, characterization and effect on thermal decomposition for RDX, HMX and AP

Two novel multiligand coordination complexes of Ni(II), [Ni(en)3]AZT·THF (1) (en = ethylene diamine, THF = tetrahydrofuran) and [Ni(AZT)(pn)2]n (2) (pn = propylene diamine), were prepared from the corresponding Ni salts and have been structurally characterized by elemental analysis, Fourier transform infrared spectroscopy and single crystal X-ray diffraction. The results show that both 1 and 2 crystallize in the triclinic space group P. 1 presents a zero-dimensional unit, while 2 exhibits a one-dimensional zigzag chain. Under nitrogen, the thermal decomposition process and the kinetic parameters of the two complexes were studied by TG-DTG and DSC technologies. The non-isothermal kinetic parameters were calculated by Kissingers and Ozawa–Doyles methods. Furthermore, the compounds were explored as additives to promote the thermal decomposition of cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX) and ammonium perchlorate (AP) by differential scanning calorimetry.

Stabilization of the Pentazolate Anion in a Zeolitic Architecture with Na20N60 and Na24N60 Nanocages

The experimental detection and synthesis of pentazole (HN5 ) and its anion (cyclo-N5- ) have been actively pursued for the past hundred years. The synthesis of an aesthetic three-dimensional metal-pentazolate framework (denoted as MPF-1) is presented. It consists of sodium ions and cyclo-N5- anions in which the isolated cyclo-N5- anions are preternaturally stabilized in this inorganic open framework featuring two types of nanocages (Na20 N60 and Na24 N60 ) through strong metal coordination bonds. The compound MPF-1 is indefinitely stable at room temperature and exhibits high thermal stability relative to the reported cyclo-N5- salts. This finding offers a new approach to create metal-pentazolate frameworks (MPFs) and enables the future exploration of interesting pentazole chemistry and also related functional materials.

Crystal structure transformation and step-by-step thermal decomposition behavior of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate

The crystal structure transformation and step-by-step thermal decomposition behavior of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) under thermal stimulation were studied and the whole process included thermal expansion, primary decomposition and secondary decomposition. The thermal expansion and primary decomposition of TKX-50 were studied using in situ powder X-ray diffraction (in situ XRD) together with Rietveld refinement, by which the crystal structure transformation process can be accurately traced. The results showed that the thermal expansion of TKX-50 was anisotropic. In particular, the a-axis exhibited a negative thermal expansion (NTE) that may be attributed to the distortion of the six-membered ring, which results in H-transfer between the cation and dianion. The crystal structure of the intermediate product after primary decomposition was also obtained. The secondary decomposition process was analysed using thermogravimetric-differential scanning calorimetry (TG-DSC) due to the safety risk of TKX-50 analyzed by in situ XRD. The crystal structure transformation process from TKX-50 to the intermediate product under heat stimulation was deduced. Meanwhile, the morphological change of the whole process was obtained using hot stage microscopy (HSM). Combined with TG-FTIR technology, the gaseous decomposition products at each step were analysed and the thermal decomposition mechanism of TKX-50 was proposed. This study further reveals the thermal decomposition behavior of TKX-50 and is helpful for better understanding the thermal decomposition mechanism.

Three-dimensional hierarchical 2,2,4,4,6,6-hexanitrostilbene crystalline clusters prepared by controllable supramolecular assembly and deaggregation process

A facile chemical template method named supramolecular assembly and deaggregation was used to prepare three-dimensional (3D) hierarchical 2,2,4,4,6,6-hexanitrostilbene (HNS) crystalline clusters. Dioxane was used as the guest molecule for guidance in the assembly process. The 3D hierarchical HNS crystalline clusters possess multiple distributions of particle size and pore size, which results in significantly different safety performance compared to raw HNS. Furthermore, the formation mechanism of these unique structures was proposed based on the experimental results. This work provides a convenient method to prepare hierarchical energetic materials with porous micro/nano structures and other hierarchical functional materials such as catalysts, adsorbents, micro reactors and sensors.

Raman spectroscopy coupled with principal component analysis to quantitatively analyze four crystallographic phases of explosive CL-20

The polymorphic quantitative analysis of explosives is very important for national defense and security inspection. However, conventional analytical methods are inaccurate and time-consuming because of the complexity of the polymorphic explosive samples. In this paper, we established a new method of polymorphic quantitative determination in a simple, sensitive, and accurate way. High quality spectra of the four phases of the explosive CL-20 were obtained using a compact Raman spectrometer, and QM calculations were performed to confirm the tentative assignment of the most predominant Raman peaks. Principal component analysis (PCA) of the data was performed to understand the factors affecting the spectral variation across the entire Raman region of the four phases of CL-20 and to calculate the characteristic Raman shift region. In addition, different characteristic peaks were selected according to the PCA and QM calculation results, and a new method for the quantitative determination of polymorphic impurities in e-CL-20 was also set up. The detection level for the polymorphic impurities was determined to be below 1%, and the standard deviation was less than ±0.5%. This new method is of significant importance for the quality control of synthesis and production not only in explosives, but also in pharmaceuticals, agrochemicals, and optics industries.