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In this study, a series of H‐bonded arylamide foldamers bearing benzoselenadiazole ends with solvent‐responsive properties have been synthesized. In dichloromethane or dimethyl sulfoxide solvents, the molecules exhibit meniscus or linear structures, respectively, which can be attributed to the unique intramolecular hydrogen bonding behavior evidenced by 1D 1H NMR and 2D NOESY spectra. UV‐vis spectroscopy experiments show that the absorption wavelength of H‐bonded arylamide foldamers are significantly red‐shifted due to the presence of benzoselenadiazole group. In addition, the crystal structures reveal that effective intermolecular dual Se ⋅ ⋅ ⋅ N interactions between benzoselenadiazole groups induce further assembly of the monomers. Remarkably, supramolecular linear and double helices structures are constructed under the synergistic induction of intramolecular hydrogen bonding and intermolecular chalcogen bonding. Additionally, 2D DOSY diffusion spectra and theoretical modelling based on density functional theory (DFT) are performed to explore the persistence of intermolecular Se ⋅ ⋅ ⋅ N interactions beyond the crystalline state. [ABSTRACT FROM AUTHOR]

Azide compounds are widely used and especially, polymers bearing pendant azide groups are highly desired in numerous fields. However, harsh reaction conditions are always mandatory to achieve full azidation, causing severe side reactions and degradation of the polymers. Herein, we report the design and preparation of two azide ionic liquids (AILs) with azide anion and triethylene glycol (E3)‐containing cation, [P444E3][N3] and [MIME3][N3]. Compared with the traditional sodium azide (NaN3) approach, both AILs showed much higher reaction rates and functional‐group tolerance. More importantly, they could act as both reagents and solvents for the quantitative azidation of various polymeric precursors under mild conditions. Theoretical simulations suggested that the outstanding performance of AILs originated from the existence of ion pairs during the reaction, and the E3 moieties played a crucial role. Lastly, after the reaction, the AILs could be easily regenerated, presenting a safer, greener, and highly efficient synthesis route for azide polymers. [ABSTRACT FROM AUTHOR]

Air gun arrays are designed to generate strong energy pulses of less than 100 Hz for offshore oil and gas exploration. In shallow seas, due to the directivity of air gun arrays, the complex propagation conditions and the limitations of acquisition methods, it is difficult to accurately evaluate the spatial time and frequency transmission characteristics of airguns. To alleviate the existing lack of knowledge about the transmission characteristics of air gun pulses in the shallow waters of the Bohai Sea, we analysed three‐dimensional ocean bottom cable seismic data collected during a seismic survey in the Bohai Sea, China, in June 2017, which were used to evaluate the reception level, frequency domain characteristics and spatial distribution characteristics within a 5.55 × 5.575 km area. The results showed that in shallow water, multipath propagation causes downfrequency chirplike sounds and an increased sound field. Within 0.3 km, the transmission model follows a cylindrical diffusion, and the sound loss rate decreases as the transmission distance increases until reaching 8 km. Signal capture by the sound channel results in a high transmission loss frequency band, whereas multimode interference weakens the transmission loss. The gun array directivity and the transmission channel are the two main factors affecting the acoustic field. This research provides an improved understanding of the acoustic field of airguns in the Bohai Sea, which can benefit the acoustic modelling of air gun arrays, the design of future seismic exploration projects and the conservation of marine life. [ABSTRACT FROM AUTHOR]

Iron (Fe), sulfur (S), and molybdenum (Mo) geochemistry in marine sediments impacted by hydrothermal plumes and/or cold seeps is complex and has not been systematically documented. Here we characterize Fe, S, and Mo diagenesis in sediments between the Minami‐Ensei Knoll hydrothermal field and a cold‐seep site of the middle Okinawa Trough. Results show that distances away from the hydrothermal field and the steep trough slope may significantly affect the transport of hydrothermal Fe. The transformation of hydrothermal reactive Fe to poorly reactive or unreactive Fe‐bearing phyllosilicates decreased the relative fractions of highly reactive Fe (FeHR) in total Fe (FeHR/FeT). Despite this, the standing stocks of Fe oxides in the methane‐free sediments have not been dampened, indicating no net impacts of hydrothermal Fe inputs on the size of Fe oxides. In the methane‐free sediments, low ratios of total reduced inorganic sulfide (TRIS) to total organic carbon (TOC) (TRIS/TOC), highly 34S‐depleted pyrite, and low Mo contents suggest that organoclastic sulfate reduction is at low rates and plays a limited role in carbon cycle. In the cold‐seep sediments, however, intense sulfate reduction coupled to anaerobic methane oxidation significantly elevate TRIS/TOC ratios, Mo enrichment, and isotope compositions of Mo and pyrite‐S. This pathway is expected to be important in carbon cycle in the basin due to the wide occurrence of cold seeps. Our results highlight the important controls of the local extreme depositional/diagenetic conditions on sedimentary S and Mo records, with implications for the reconstruction of paleoredox states of the past earth's surface. Plain Language Summary: Submarine methane‐rich cold seeps and hydrothermal venting exert important influences on the geochemistry of iron, sulfur, and molybdenum. However, the influences of the two extreme environments on the three interlinked elements in seafloor have not been well documented. Here, we used solid‐phase chemistry of four sediment cores located between a hydrothermal field and a cold‐seep site in the middle Okinawa Trough to document the impacts of the two extreme environments on the geochemistry of iron, sulfur, and molybdenum. Results show that hydrothermal Fe signature in the sediments is largely controlled by the distances away from the hydrothermal field and the steep slope of the trough; the hydrothermal Fe inputs have no net impacts on sedimentary iron oxide contents due to simultaneous inactivation of reactive Fe. In the methane‐free sediments, sulfate reduction (SR) is coupled mainly to oxidation of sedimentary organic carbon. In the cold‐seep site, however, SR coupled to anaerobic methane oxidation is the main pathway of carbon cycle, leading to significant enrichments of molybdenum and isotopically heavy pyrite. The differences highlight the important control of local extreme depositional/diagenetic conditions on geochemical records of iron, sulfur, and molybdenum, with implications for the reconstruction of paleoredox states in the past. Key Points: Distances away from the vent, steep basin slope and Fe inactivation control the signature of hydrothermal Fe in the basin sedimentsLow lability of organics limits sulfate reduction (SR) in CH4‐free sediments, while CH4 largely facilitates SR in cold‐seep sedimentsLocal extreme conditions exert key controls on S‐Fe‐Mo diagenesis in the basin [ABSTRACT FROM AUTHOR]

Bulk Ti–Al based alloys with an approximate mass of 30 g are first prepared by electromagnetic levitation. The microstructures and the compression properties of Ti‐45%Al‐z%V alloys (z = 4, 8, and 12, atomic percent) at room and high temperatures are studied by experiments. The relationship between V content and the mechanical properties of γ and α2 intermetallics has been investigated by first‐principle calculations. It is clarified that V addition controls the phase contents and the microstructure characteristics. With the increase of V content, the microstructures of Ti‐45%Al‐4%V and Ti‐45%Al‐12%V are dominated by the phase transformations of α → γ and α → α2, respectively. Ti‐45%Al‐4%V alloy is mainly constituted of fine full lamellar γ phase while Ti‐45%Al‐12%V alloy is composed of coarsening lath α2 phase. Besides, the Young's modulus of Ti‐45%Al‐12%V alloy is smaller than that of Ti‐45%Al‐4%V alloy at 300 K, but the yield stress and ultimate compression stress are larger than that of Ti‐45%Al‐4%V alloy. The differences are attributed to the change of the main phase from γ to α2 and the mechanical properties of crystals changed by V addition. In addition, V addition changes the Young's modulus of α2 crystal from isotropy to anisotropy. [ABSTRACT FROM AUTHOR]

Here we employ density functional theory calculations to systematically investigate the underlying mechanism of Cu(OTf)2‐catalyzed [3+2] cycloaddition reactions in the synthesis of CF3‐substituted pyrazolidines. About eight possible initial configurations of the [3+2] reaction is considered, and all relevant reactants, transition states, and products are optimized. Based on these structures, internal reaction coordinate paths, and wavefunction analysis results, we conclude that the Cu(OTf)2‐catalyzed [3+2] cycloaddition follows a concerted asynchronous mechanism. The CN bond forms immediately after the formation of the CC bond. Among the eight reaction paths, the energy barrier for the [3+2] reaction that leads to the CF3‐substituted syn‐pyrazolidine is the lowest, ∼5.4 kcal/mol, which might result in the diastereoselectivity that is observed in the experiment. This work not only gives the detailed mechanism of the Cu(OTf)2‐catalyzed [3+2] cycloaddition but can also be helpful for the future designation of Cu(OTf)2‐based cycloaddition processes. [ABSTRACT FROM AUTHOR]

Natural gas hydrates have been hailed as a new and promising unconventional alternative energy, especially as fossil fuels approach depletion, energy consumption soars, and fossil fuel prices rise, owing to their extensive distribution, abundance, and high fuel efficiency. Gas hydrate reservoirs are similar to a storage cupboard in the global carbon cycle, containing most of the world's methane and accounting for a third of Earth's mobile organic carbon. We investigated gas hydrate stability zone burial depths from the viewpoint of conditions associated with stable existence of gas hydrates, such as temperature, pressure, and heat flow, based on related data collected by the global drilling programs. Hydrate‐related areas are estimated using various biological, geochemical and geophysical tools. Based on a series of previous investigations, we cover the history and status of gas hydrate exploration in the USA, Japan, South Korea, India, Germany, the polar areas, and China. Then, we review the current techniques for hydrate exploration in a global scale. Additionally, we briefly review existing techniques for recovering methane from gas hydrates, including thermal stimulation, depressurization, chemical injection, and CH4–CO2 exchange, as well as corresponding global field trials in Russia, Japan, United States, Canada and China. In particular, unlike diagenetic gas hydrates in coarse sandy sediments in Japan and gravel sediments in the United States and Canada, most gas hydrates in the northern South China Sea are non‐diagenetic and exist in fine‐grained sediments with a vein‐like morphology. Therefore, especially in terms of the offshore production test in gas hydrate reservoirs in the Shenhu area in the north slope of the South China Sea, Chinese scientists have proposed two unprecedented techniques that have been verified during the field trials: solid fluidization and formation fluid extraction. Herein, we introduce the two production techniques, as well as the so‐called "four‐in‐one" environmental monitoring system employed during the Shenhu production test. Methane is not currently commercially produced from gas hydrates anywhere in the world; therefore, the objective of field trials is to prove whether existing techniques could be applied as feasible and economic production methods for gas hydrates in deep‐water sediments and permafrost zones. Before achieving commercial methane recovery from gas hydrates, it should be necessary to measure the geologic properties of gas hydrate reservoirs to optimize and improve existing production techniques. Herein, we propose horizontal wells, multilateral wells, and cluster wells improved by the vertical and individual wells applied during existing field trials. It is noteworthy that relatively pure gas hydrates occur in seafloor mounds, within near‐surface sediments, and in gas migration conduits. Their extensive distribution, high saturation, and easy access mean that these types of gas hydrate may attract considerable attention from academia and industry in the future. Herein, we also review the occurrence and development of concentrated shallow hydrate accumulations and briefly introduce exploration and production techniques. In the closing section, we discuss future research needs, key issues, and major challenges related to gas hydrate exploration and production. We believe this review article provides insight on past, present, and future gas hydrate exploration and production to provide guidelines and stimulate new work into the field of gas hydrates. [ABSTRACT FROM AUTHOR]

Abstract: A new 3D framework {[Eu2Cu(IN)5(CO3)(H2O)] ⋅3 H2O}n (1) was obtained and structurally characterized, containing CuI and an unusual lanthanide duplex chain. The luminescent explorations of compound 1 suggest that 1 could emit the characteristic emission of CuI, and 1 can act as the luminescent sensor of ClO− with the detection limit of 10−5  m. Notably, 1 represents the first example of MOF‐based sensor for detecting ClO−. [ABSTRACT FROM AUTHOR]

In the past thirty years, azido polymers have attracted wide attention in the field of energetic materials. Currently, the synthesized azido polymers have linear structure. In the present research, hyperbranched poly-3-azidomethyl-3- oxetane (HBPAMHMO) was synthesized using an AB2 monomer, and its physical and chemical properties were studied. The results showed that the molecular weight of HBPAMHMO increased along with the increasing ratio of r ([monomer]0/[initiator]0), together with very narrow PDI (from 1.12 to 1.34), and moreover, the degree of branching increased along with the increase in polymerization temperature. As compared to linear azido polymer with similar structure, it has lower glass transition temperature, sensitivity, higher combustion heat and mechanical properties, suggesting a great prospect for numerous applications. [ABSTRACT FROM AUTHOR]

Two nickel(II) complexes were synthesized and structurally as well as magnetically characterized by using two positional isomeric nitronyl nitroxide radical ligands and H3cda as co-ligand: [Ni(NIToPy)(cda)]H2O ·CH3OH ( 1) and [Ni(IM4Py)2(cda)H2O] ( 2) [NIToPy = 2-(3′-pyridinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide; IM4Py = 2-(4′-pyridinyl)-4,4,5,5-tetramethylimidazoline-l-oxyl; H3cda = 4-hydroxypyridine-2,6-dicarboxylic acid]. Single-crystal structures analyses show that both complexes have similar mononuclear structures, in which the central NiII ions are hexacoordinated with a distorted octahedral arrangement. The magnetic properties of 1 and 2 were studied, and antiferromagnetic interactions between NiII ion and radicals are observed. [ABSTRACT FROM AUTHOR]

Three multi-dentate 1, 2,4-triazole derivative ligands containing different 4-substituted groups, namely N-1, 2,4-triazol-4-yl(pyridin-3-yl)methylenimine (L1), N-1, 2,4-triazol- 4-yl(pyridin-4-yl)methylenimine (L2), and 4-(2-pyridine)-1, 2,4-triazole (L3) were used to isolate five iron(II) and zinc(II) coordination frameworks, [Zn(μ2-L1)Cl2] ( 1), [Zn(μ2-L2)Br2] ( 2), [Fe(L1)2(NCS)2(H2O)2] ( 3), [Fe(L3)2(dca)2(H2O)2] ( 4), and [Fe(L3)2(μ2-dca)] ( 5) (dca = dicyanamide anion). When different zinc(II) salts were used to react with L1 and L2 under solvothermal conditions, two one-dimensional (1D) zinc(II) coordination frameworks 1 and 2 containing four-coordinate central zinc(II) atoms were isolated. 1 is a 3D achiral supra-molecular framework, whereas 2 is a 3D chiral supra-molecular framework containing helical chains on a 21 axis. 3 is a mono-nuclear iron(II) coordination framework containing six-coordinate central FeII atoms. When L3 was employed, mono-nuclear iron(II) framework 4 and 1D iron(II) chain 5 could be isolated when different amounts of Nadca were introduced into the reaction system. Variable-temperature magnetic susceptibility data of 3- 5 were recorded in the 2-300 K temperature range indicating weak anti-ferromagnetic interactions. The solid-state luminescent properties of coordination polymers 1 and 2 were also investigated at room temperature. [ABSTRACT FROM AUTHOR]

Noble-metal-derived functional materials have played indispensable roles in the reduction of dye under aqueous conditions; however, their cost and separation are great limitations on their wider practical applications. Therefore, an alternative preparation of comparable materials with low cost and good ease of separation is required. Herein magnetic microspheres (i.e., Fe3O4/Cu) were synthesized through a green single-step solvothermal method for the first time with ethylene glycol serving as reductant and reaction media. The prepared materials were characterized by means of powder Xray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, energy- dispersive X-ray spectrometry, a vibrating sample magnetometer, and so forth. Additionally, by employing the reduction of 4-nitrophenol to 4-aminophenol as a model reaction, the effects of preparation time and the initial dosage of Cu(NO3)2 on the rate constant of the catalytic reduction reaction were systematically investigated. Moreover, the obtained hybrid nanocatalysts were also applied to reduce and degrade common organic dyes (rhodamine B and methylene blue) in the presence of NaBH4. Quite significantly, it was shown that it could catalytically degrade different organic dyes with excellent catalytic performance and high stability in recycled reactions up to five times. More interestingly, the material can be easily separated from the catalytic system for further use. [ABSTRACT FROM AUTHOR]

A BAMO-AMMO alternative block (BAAB)-based thermoplastic composite propellant with 80 % solid content was prepared using BAAB energetic thermoplastic elastomer (ETPE) as the binder, and the formulation was optimized through energy calculation. The densities, heats of explosion, glass-transition temperatures, and mechanical properties of the samples were determined by surface tension measurements, oxygen bomb calorimetry, differential scanning calorimetry and static tensile tests, respectively. The results showed that this composite propellant can reach a standard theoretical specific impulse of 275.45 s (10 MPa), a density of 1.8102 g cm−3, a heat of explosion of 6256 kJ kg−1, a Tg of −50.46 °C, a tensile strength of 1.56 MPa and an elongation at break of 20 %, thus presenting a superior comprehensive property to BAMO-AMMO random block (BARB)-based thermoplastic composite propellant. [ABSTRACT FROM AUTHOR]

A layer-by-layer deposition strategy was employed for the immobilization of tungstophosphoric acid (HPW) onto a pentaethylenehexamine (PEHA)-grafted ZrSBA-15 framework to a give HPW/PEHA/ZrSBA-15 composite. The resulting composite was characterized by XRD, SEM, TEM, FTIR, thermogravimetric analysis, N2 sorption, and X-ray photoelectron spectroscopy, and these methods showed that the composite was stable in polar environments. These properties were attributed to the method of preparation, which ensured that a dense and stable array of HPW was encapsulated within the pores of PEHA-modified ZrSBA-15. In the H2O2-mediated oxidation of benzyl alcohol, the 25 % HPW/PEHA/ZrSBA-15 catalyst exhibited high selectivity (>99 %) for benzaldehyde. Moreover, the oxidation reaction was performed under solvent-free conditions, and the catalyst was recycled several times with negligible loss in selectivity and conversion. This HPW-based catalyst was also efficient at selectively oxidizing other benzylic and alkyl alcohols to the corresponding aldehydes. [ABSTRACT FROM AUTHOR]

The back cover picture shows that we synthesized a series of novel hyperbranched azido polymers namely poly‐3‐azidomethyl‐3‐hydroxymethyl oxetanes (HBPAMHMOs) using cationic ring opening polymerization. GPC, 13C NMR and MALDI‐TOF results indicate these polymers have controllable molecular weight and degree of branching, with narrow molecular weight distributions. To take a step forward, we prepared HBPAMHMO‐based energetic binder film. Compared to its linear analogues, HBPAMHMO shows lower glass transition temperature, sensitivity, higher combustion heat and mechanical properties, suggesting a great prospect for numerous applications. More details can be found in the Full Paper by Dr. Chi Zhang et al. on page 1037. [ABSTRACT FROM AUTHOR]

The isotypic compounds (III) crystallize in the trigonal space group P3121 with Z = 3 (single crystal XRD) and feature a three-dimensional network which is formed by 6-connected sulfate, Ln3+, and Na+ ions. [ABSTRACT FROM AUTHOR]

The title complex, [Tb(2)(C(6)H(4)NO(2))(6)(H(2)O)(4)](n), was isolated under hydro-thermal conditions using the ligand pyridine-4-carb-oxy-lic acid (HL) and Tb(2)O(3). The deprotonated L(2-) ligands adopt bridging coordination modes. The central Tb(III) atom is bridged by L(2-) ligands, forming a polymeric chain parallel to the a axis. Supra-molecular O-H⋯N inter-actions link the chains, building up a layer parallel to (010). O-H⋯O hydrogen bonds also occur. Two of the pyridine rings are disordered by rotation around the central C-N direction with occupancy ratios of 0.53 (1):0.47 (1).

In the title silver(I) coordination polymer, {[Ag(2)(C(6)H(5)N(2)O(2))(2)(H(2)O)(2)]·2H(2)O}(n), the [Ag(2)(μ(2)-H(2)O)(H(2)O)] cores are extended by anti-parallel 5-methyl-pyrazine-2-carboxyl-ate (L) ligands, forming a novel double-chain structure. Both Ag(+) cations show a distorted square-pyramidal coordination. Ag1 is bonded to two water molecules, one L N atom, one N atom and one carboxylate O atom from a neighbouring L, whereas Ag2 is surrounded by two L N atoms, two L carboxylate O atoms and one bridging water molecule. O-H⋯O hydrogen-bonding inter-actions involving water clusters and carboxyl-ate O atoms link the mol-ecules into a three-dimensional supra-molecular architecture, which is further consolidated by weak C-H⋯O inter-actions and π-π stacking inter-actions [centroid-centroid distance 3.643 (5) Å].