Sodium catalytic phenylpentazole cracking: a theoretical study.

This work presents an in-depth investigation into the cracking reaction mechanism of phenylpentazole (C6H5N5) under the catalytic influence of sodium metal, utilizing density functional theory. The geometries of the reactants, transition states, intermediates, and products are meticulously optimized employing the GGA/PW91/DNP level of theory. Also, a rigorous analysis is undertaken, encompassing various key factors including configuration parameters, Mulliken charges, densities of states, and reaction energies. Three distinct reaction pathways are comprehensively examined, shedding light on the intricate details and intricacies of each pathway. The results show that a remarkable outcome in which the activation energy of the C6H5N5 cracking reaction releases N2, facilitated by catalytic metal Na, reveals a strikingly reduced value of a mere 5.2 kcal mol-1 compared to the previously reported activation energies ranging from 20 to 30 kcal mol-1. Evidently, this significantly lowered barrier can be readily surpassed at typical room temperatures, exhibiting practical applicability. Notably, the alkali metal Na effectively serves as a catalyst, successfully diminishing the activation energy required for N2 production through the pyrolysis of pentazole compounds. This breakthrough discovery provides a theoretical basis for experimental research on the low-temperature cracking of pentazole compounds. It also offers valuable insights for the development and application of new high energy density materials, contributing to the creation of a green and low-carbon circular economic system.

B, O and N Codoped Biomass-Derived Hierarchical Porous Carbon for High-Performance Electrochemical Energy Storage.

High specific surface area, reasonable pore structure and heteroatom doping are beneficial to enhance charge storage, which all depend on the selection of precursors, activators and reasonable preparation methods. Here, B, O and N codoped biomass-derived hierarchical porous carbon was synthesized by using KCl/ZnCl2 as a combined activator and porogen and H3BO3 as both boron source and porogen. Moreover, the cheap, environmentally friendly and heteroatom-rich laver was used as a precursor, and impregnation and freeze-drying methods were used to make the biological cells of laver have sufficient contact with the activator so that the layer was deeply activated. The as-prepared carbon materials exhibit high surface area (1514.3 m2 g-1), three-dimensional (3D) interconnected hierarchical porous structure and abundant heteroatom doping. The synergistic effects of these properties promote the obtained carbon materials with excellent specific capacitance (382.5 F g-1 at 1 A g-1). The symmetric supercapacitor exhibits a maximum energy density of 29.2 W h kg-1 at a power density of 250 W kg-1 in 1 M Na2SO4, and the maximum energy density can reach to 51.3 W h kg-1 at a power density of 250 W kg-1 in 1 M BMIMBF4/AN. Moreover, the as-prepared carbon materials as anode for lithium-ion batteries possess high reversible capacity of 1497 mA h g-1 at 1 A g-1 and outstanding cycling stability (no decay after 2000 cycles).

Divergent Regioselective Csp2-H Difluoromethylation of Aromatic Amines Enabled by Nickel Catalysis.

Herein, the first catalytic protocol for nickel-catalyzed ortho or para position difluoromethylation of various aromatic amines has been developed with the assistance of a bidentate phosphine ligand, offering an invaluable synthesis means to construct extensive p-difluoromethylated products and difluorooxindole derivatives with significant functional fragments. Furthermore, the gram-scale reaction, broad substrate scope, excellent functional-group compatibility, late-stage difluoromethylation of pesticides, and even formal synthesis of HDAC6 inhibitors further demonstrate the usefulness of this method.

Photo-Fenton Process over an Fe-Free 3%-CuO/Sr0.76Ce0.16WO4 Photocatalyst under Simulated Sunlight.

Photo-Fenton is a promising photocatalytic technology that utilizes sunlight. Herein, an Fe-free 3%-CuO/Sr0.76Ce0.16WO4 photocatalyst was synthesized to apply simulated wastewater degradation via a photo-Fenton process under simulated sunlight. The photodegradation efficiency of RhB solution over the 3%-CuO/Sr0.76Ce0.16WO4 photocatalyst is 93.2% in the first 3 h; its photocatalytic efficiency remains at 91.6% even after three cycle experiments. The kinetic constant of the 3%-CuO/Sr0.76Ce0.16WO4 photocatalyst is 0.0127 min-1, which is 2.8-fold that of an intrinsic Sr0.76Ce0.16WO4 sample. The experiment of radical quenching revealed that the photogenerated electrons and holes are transferred to CuO to form hydroxyl radicals. Besides, the photocatalyst was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), diffused reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) measurements. It has some reference significance for the design of iron-free photocatalysts.

Novel Technology for Vanadium and Chromium Extraction with KMnO4 in an Alkaline Medium.

This paper focused on the oxidation-alkaline extraction process of vanadium-chromium-reducing residue. The affected parameters including reaction temperature, KMnO4 dosage, reaction time, NaOH dosage, and liquid-to-solid ratio on the extraction process were investigated. The E-pH diagram and the thermodynamic analysis indicated that KMnO4 was suitable for the oxidation of low-valence vanadium and chromium. Vanadium (97.24%) and chromium (56.20%) were extracted under the following optimal reaction conditions: reaction temperature of 90 °C, reaction time of 90 min, dosage of KMnO4 at m(KMnO4)/m(residue) = 0.40, dosage of NaOH at m(NaOH)/m(residue) = 0.30, and liquid-to-solid ratio at 5:1 mL/g. The extraction process of vanadium was controlled by the reactant through the solid product layer and the extraction kinetics behavior fitted well with the shrink core model with an E a of 15.37 kJ/mol. At the same time, the surface chemical reaction was the controlling step for chromium extraction, which was difficult with an E a of 39.78 kJ/mol.

Discovery of an Oxidative System for Radical Generation from Csp3-H Bonds: A Synthesis of Functionalized Oxindoles.

A facile and versatile method for generating radicals from Csp3-H bonds under metal-free and organic-peroxide-free conditions was developed. By combining safe persulfate and low-toxic quaternary ammonium salt, a wide variety of Csp3-H compounds including ethers, (hetero)aromatic/aliphatic ketones, alkylbenzenes, alkylheterocycles, cycloalkanes, and haloalkanes were selectively activated to generate the corresponding C-centered radicals, which could be further captured by N-arylacrylamides to deliver the valuable functionalized oxindoles. Good functional group tolerance was demonstrated. The useful polycarbonyl compound and esters were also modified with the strategy. Moreover, the combination can also be applied to the practical coupling between simple haloalkanes and N-hydroxyphthalimide (NHPI).

Thermodynamic and Kinetic Studies on Adsorption of Vanadium with Glutamic Acid.

Many hydrometallurgy methods, including chemical precipitation, ion exchange, solvent extraction, and adsorption, have been used to recover vanadium from vanadium solution, but the final step of these methods involved precipitation with ammonium salts, high concentrations of which are harmful to the environment. The key point is to find a new compound to replace ammonium salts without reducing the vanadium precipitation efficiency. The adsorption process of vanadium with glutamic acid is investigated. The effects of experimental factors, including dosage of glutamic acid, reaction temperature, concentration of H2SO4, and reaction time, on the adsorption process are investigated. The results show that nearly 91.66% vanadium is adsorbed under the following reaction conditions: reaction temperature of 90 °C, H2SO4 concentration of 20 g/L, glutamic acid dosage at n(glu)/n(V) = 3.0:1, and reaction time of 60 min. The response surface methodology is applied to optimize the reaction conditions. The analysis results indicate that the reaction temperature has the greatest effect on the adsorption efficiency of vanadium and the influence of experimental factors follows the order: reaction temperature > dosage of glutamic acid to vanadium > reaction time > concentration of H2SO4. The pseudo-second-order model is selected to describe well the adsorption kinetic behavior, and the thermodynamic analysis results indicate that the adsorption process of vanadium is unspontaneous and exothermic. The results will be useful for further applications of glutamic acid, and they provide a bright future for vanadium recovery.

FeNb2O6/reduced graphene oxide composites with intercalation pseudo-capacitance enabling ultrahigh energy density for lithium-ion capacitors.

Lithium-ion capacitors (LICs), which combine the characteristics of lithium-ion batteries and supercapacitors, have been well studied recently. Extensive efforts are devoted to developing fast Li+ insertion/deintercalation anode materials to overcome the discrepancy in kinetics between battery-type anodes and capacitive cathodes. Herein, we design a FeNb2O6/reduced graphene oxide (FNO/rGO) hybrid material as a fast-charge anode that provides a solution to the aforementioned issue. The synergetic combination of FeNb2O6, whose unique structure promotes fast electron transport, and highly conductive graphene shortens the Li+ diffusion pathways and enhances structural stability, leading to excellent electrochemical performance of the FNO/rGO anode, including a high capacity (770 mA h g-1 at 0.05 A g-1) and long cycle stability (95.3% capacitance retention after 500 cycles). Furthermore, the FNO/rGO//ACs LIC achieves an ultrahigh energy density of 135.6 W h kg-1 (at 2000 W kg-1) with a wide working potential window from 0.01 to 4 V and remarkable cycling performance (88.5% capacity retention after 5000 cycles at 2 A g-1).

Simultaneous determination of Acetaminophen and dopamine based on a water-soluble pillar[6]arene and ultrafine Pd nanoparticle-modified covalent organic framework nanocomposite.

While numerous sensing strategies have been applied in the determination of Acetaminophen (AP), dopamine (DA), and ascorbic acid (AA), the selectivity is always a critical challenge based on their similar structure and function. Accordingly, the development of a highly selective sensing method is not only necessary but also crucial. In this study, a novel electrochemical sensing platform for the simultaneous determination of AP and DA has been successfully constructed based on a multifunctional nanocomposite (WP6-Pd-COF) of water-soluble pillar[6]arene (WP6), ultrafine Pd nanoparticles, and triethylene glycol-modified covalent organic framework (COF). Pd nanoparticles with an average size of 4.2 nm are prepared by reducing K2PdCl4 under the stabilization of oxygen-rich COF, which shows superior catalytic activity in electrochemical detection. A supramolecular host-guest recognition system introduced between WP6 and analytes (AP, DA, and AA) can effectively recognize AP and DA, implying the simultaneous determination of AP and DA by this approach. The electrode, best operated at a working potential range from -0.2 to 0.8 V (vs. Hg/Hg2Cl2), works in the concentration ranges of 0.2-8 µM for DA and 0.1-7.5 µM for AP, and has a detection limit of 0.06 µM for DA and 0.03 µM for AP (S/N = 3). Therefore, this study presents potential application values in sensing, catalysis, and other fields.

Nanocomposite Based on Organic Framework-Loading Transition-Metal Co Ion and Cationic Pillar[6]arene and Its Application for Electrochemical Sensing of l-Ascorbic Acid.

In this study, we constructed a highly sensitive and selective electrochemical sensing strategy for l-ascorbic acid (AA) based on a covalent organic framework (COF)-loading non-noble transition metal Co ion and macrocyclic cationic pillar[6]arene (CP6) nanocomposite (CP6-COF-Co). The COF plays a crucial role in anchoring the Co ion according to its crystalline porous and multiple coordination sites and has an outstanding performance for building an electrochemical sensing platform based on a unique two-dimensional structure. Accordingly, the transition-metal Co ion can be successfully anchored on the framework of COF and shows strong catalytic activity for the determination of AA. Moreover, introduction of host-guest recognition based on CP6 and AA can bring new properties for enhancing selectivity, sensitivity, and practical application in real environment. Host-guest interactions between CP6 and AA were evaluated by the 1H NMR spectrum. When compared with other literatures, our method displayed a lower determination limit and broader linear range. To the best of our knowledge, this is the first study carried out for the non-noble transition-metal Co ion, COF, and pillar[6]arene hybrid material in sensing field, which has a potential value in sensing, catalysis, and preparation of advanced multifunction materials.

Photocatalytic Reduction of Cr(VI) on a 3.0% Au/Sr0.70Ce0.20WO4 Photocatalyst.

Herein, a 3.0%-Au/Sr0.70Ce0.20WO4 sample was prepared for the photocatalytic reduction of the Cr2O7 2- ion. The photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible diffuse reflectance spectra. The Sr0.70Ce0.20WO4 sample presented a photocatalytic reduction activity that is better than those of the Ce-doped sample and the intrinsic sample. Thereafter, different metal elements, Cu, Ag, Au, and Pt, were used as cocatalysts, which were loaded on the Sr0.70Ce0.20WO4 sample. The 3.0%-Au/Sr0.70Ce0.20WO4 photocatalyst showed optimal photocatalytic reduction activity in a 8 vol % methanol solution (pH = 7) under visible light irradiation. The kinetic constant of the optimal one is 0.0039 min-1, which is 1.86 times that of the Sr0.70Ce0.20WO4 sample. The photocatalyst is stable enough after a 24 h photocatalytic experiment.

New Insights into the Stability of Anhydrous 2H-Imidazolium Fluoride and its High Dissolution Capability toward a Strongly Hydrogen-Bonded Compound.

Fluorides have been widely applied in pharmaceutical, medicinal, and materials science as well as in fine chemical manufacturing. The performance of fluorides, however, can be markedly affected by the water content. One previous study (Maiti, A.; et al. Phys. Chem. Chem. Phys. 2008, 10, 5050) suggested that anhydrous 1,3-dimethylimidazolium fluoride ([DMIm]F) was unstable since the fluoride undergoes a self-decomposition reaction. Herein we first show quantum-chemical calculation evidence that although gas-phase [DMIm]F is unstable, the bulk phase of anhydrous [DMIm]F is quite stable. We then demonstrate the successful synthesis of the anhydrous [DMIm]F compound via the reaction between 1,3-dimethylimidazolium iodide and silver fluoride. Importantly, we find that anhydrous [DMIm]F possesses a high dissolution capability toward 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), although it is known that TATB is hardly dissolved in many common organic solvents. Our Born-Oppenheimer molecular dynamics (BOMD) simulations further show that the high dissolving ability of anhydrous [DMIm]F toward TATB can be attributed to the chemical reaction between the F- anion and the TATB molecules, which disrupts the strong hydrogen-bonding interaction among the TATB molecules. Alternatively, water molecules in hydrous [DMIm]F tend to form a hydration layer around the F- anion, thereby preventing F- from reacting with the TATB molecule. This result explains why TATB is barely dissolved in hydrous [DMIm]F.

Reconciling the Debate on the Existence of Pentazole HN5 in the Pentazolate Salt of (N5)6(H3O)3(NH4)4Cl.

The successful synthesis of the pentazolate salt (N5)6(H3O)3(NH4)4Cl has received considerable attention, as it ends the long search for a method for the bulk preparation of cyclo-N5-, a molecular ring with high energy density ( Zhang , C. ; Science 2017 , 355 , 374 . ). A debate has recently arisen on the possible existence of a neutral HN5 species in the pentazolate salt ( Huang , R.-Y. ; Science 2018, 359 , eaao3672 . ; Jiang , C. ; Science 2018, 359 , eaas8953 . ). Herein, we show that the debate can be reconciled by the temperature effect on the proton transfer. At a low temperature (123 K), the proton transfer from H3O+ to cyclo-N5- is energetically unfavorable; therefore, few neutral HN5 species exist in the pentazolate salt, which is consistent with the single-crystal X-ray diffraction measurements ( Zhang , C. ; Science 2017 , 355 , 374 . ). As the temperature increases toward room temperature, endothermic proton transfer becomes increasingly feasible, promoting the formation of H2O···HN5 via H2O-H-N5 as an intermediate species. In addition, the confusion over the apparent absence of a peak in the measured infrared spectrum corresponding to the out-of-plane bending of H3O+ can be resolved by the computationally established ultrafast interconversion among the neutral and anionic species under ambient conditions.

Theoretical study of the correlation between electrostatic hazard and electronic structure for some typical primary explosives.

The electronic structures of lead styphnate, hexa(1,5-diaminotetrazole) cobalt perchlorate, lead azide, (5-cyanotetrazolato-N (2)) pentaammine cobalt perchlorate, and tris(carbohydrazide) zinc perchlorate were investigated via density functional theory. The results obtained reveal that the electrostatic spark sensitivities of these primary explosives are related to their electrostatic potentials and energy gaps. Highly sensitive primary explosives show large cell electrostatic potentials per unit volume and small energy gaps. Moreover, the energy levels of the frontier molecular orbitals play an important role in triboelectrification between an explosive and a flume. The lower the energy level of the lowest unoccupied molecular orbital of the primary explosive, the more easily it can accept electrons and accumulate negative charge.

First-principles study of electric field effects on the structure, decomposition mechanism, and stability of crystalline lead styphnate.

The electric field effects on the structure, decomposition mechanism, and stability of crystalline lead styphnate have been studied using density functional theory. The results indicate that the influence of external electric field on the crystal structure is anisotropic. The electric field effects on the distance of the Pb-O ionic interactions are stronger than those on the covalent interactions. However, the changes of most structural parameters are not monotonically dependent on the increased electric field. This reveals that lead styphnate can undergo a phase transition upon the external electric field. When the applied field is increased to 0.003 a.u., the effective band gap and total density of states vary evidently. And the Franz-Keldysh effect yields larger influence on the band gap than the structural change induced by external electric field. Furthermore, lead styphnate has different initial decomposition reactions in the presence and absence of the electric field. Finally, we find that its sensitivity becomes more and more sensitive with the increasing electric field.

First-principles study of energetic complexes (II): (5-cyanotetrazolato-N2) pentaammine cobalt (III) perchlorate (CP) and Ni, Fe and Zn analogues.

First-principles methods using the TPSS density functional level of theory with the basis set 6-31G** were applied to study (5-cyanotetrazolato-N(2)) pentaammine cobalt (III) perchlorate (CP) and Ni, Fe and Zn analogues in the gas phase. The optimized lowest-energy geometry of CP was calculated from reported experimental structural data using the TPSS method. The calculated values are in good agreement with those measured by X-ray diffraction. Ni, Fe and Zn analogues were constructed and calculated on the same basis. NBO results showed that the metal-ligand interactions have covalent character. Donor-acceptor analyses predicted that the delocalization energy E(2) decreases from Co to Zn, so the covalent nature of the complexes increases in the order Co>Fe>Ni>Zn. In addition, HOMO-LUMO composition was investigated to determine the stability of the title compounds.

A screened hybrid density functional study on energetic complexes: cobalt, nickel and copper carbohydrazide perchlorates.

The molecular geometry, electronic structure, infrared spectra and thermochemical properties of cobalt and nickel tris(carbohydrazide) perchlorates (CoCP and NiCP) as well as copper bis(carbohydrazide) perchlorate (CuCP) were investigated using the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid density functional. The results show that both perchlorate ions coordinate with the copper atom, and the interactions between copper and perchlorate are ionic, whereas all the metal-carbohydrazide interactions are covalent. Due to the delocalization from the sigma(N-H) bond orbital to the n*(M) antibond orbital, the amino stretching vibrations of these complexes show considerable red-shift compared with those of free carbohydrazide ligand. The calculated heats of reaction and formation indicate that the formations of these complexes are exothermic, and the order of their thermal stability is NiCP>CoCP>CuCP. These agree well with the experimental results. Finally, we find that there is a relationship between the energy gap and impact sensitivity.