Borosulfates are oxoanionic compounds consisting of condensed sulfur‐ and boron‐centered tetrahedra. Hitherto, they were mostly achieved from solvothermal syntheses in SO3‐enriched sulfuric acid, or ...from reactions with the superacid HB(HSO4)4. The crystal structures are very similar to those of the corresponding class of silicates and their substitution variants, especially regarding the typical structural motif of corner‐sharing tetrahedra. However, the borosulfates are supposed to be even more versatile, because (BO3) units might also be part of the anionic network. The following article deals with detailed reports on the different synthesis strategies, the crystal chemistry of borosulfates in comparison to silicates, and their hitherto identified properties.
Borosulfates are structurally similar to silicates. Their anionic subunits consist of alternating (SO4) and (BO4) tetrahedra forming oligomers, single and multiple chains, layers and extended 3D network structures. The review deals with detailed reports on the different synthesis strategies, the crystal chemistry of borosulfates in comparison to silicates, and their hitherto identified properties.
The position of deposits and ore bodies for the underground mining in the underground mine Jama Bor, in relation to the terrain surface, old works of the Jama and Open Pit in Bor, and in relation to ...the mining infrastructure limits the selection of excavation methods with the applied technologies up to now. This paper presents the block method of excavation with backfilling the excavated space with the paste backfill of the Bor River deposit.
Solar energy has received considerable attention over the past few decades, due to its importance as a green and renewable energy. Low-cost solar-grade silicon production is critical for the ...widespread use of solar cells. Conventional routes (e.g., modified Siemens process: chlorosilane and hot filament) have still dominated the production of solar-grade silicon. The metallurgical route offers benefits in the productivity and cost, but efficient removal of boron is one of the most daunting challenges in front of us. This paper reviews thermodynamic and kinetic properties (solubility, diffusivity, diffusion coefficients, mass transfer rate, and activity coefficient) of boron and recent research topics (slag treatment, solvent refining, gas injection, plasma treatment, and acid leaching) for boron removal.
Developing strong visible‐light‐absorbing (SVLA) earth‐abundant photosensitizers (PSs) for significantly improving the utilization of solar energy is highly desirable, yet it remains a great ...challenge. Herein, we adopt a through‐bond energy transfer (TBET) strategy by bridging boron dipyrromethene (Bodipy) and a CuI complex with an electronically conjugated bridge, resulting in the first SVLA CuI PSs (Cu‐2 and Cu‐3). Cu‐3 has an extremely high molar extinction coefficient of 162 260 m−1 cm−1 at 518 nm, over 62 times higher than that of traditional CuI PS (Cu‐1). The photooxidation activity of Cu‐3 is much greater than that of Cu‐1 and noble‐metal PSs (Ru(bpy)32+ and Ir(ppy)3+) for both energy‐ and electron‐transfer reactions. Femto‐ and nanosecond transient absorption and theoretical investigations demonstrate that a “ping‐pong” energy‐transfer process in Cu‐3 involving a forward singlet TBET from Bodipy to the CuI complex and a backward triplet‐triplet energy transfer greatly contribute to the long‐lived and Bodipy‐localized triplet excited state.
Harvest home: Through‐bond energy transfer (TBET) strategy was employed to construct a low‐cost copper(I) photosensitizer (PS) with high visible‐light harvesting ability and a long‐lived excited state. For energy‐ and electron‐transfer reactions it dramatically outperforms traditional Cu‐PS and noble‐metal PSs (Ru(bpy)32+ and Ir(ppy)3+).
A series of Boron-dipyrromethene (Bodipy) dyes were used as photosensitizers for photochemical hydrogen production in conjunction with CoIII(dmgH)2pyCl (where dmgH = dimethylglyoximate, py = ...pyridine) as the catalyst and triethanolamine (TEOA) as the sacrificial electron donor. The Bodipy dyes are fully characterized by electrochemistry, X-ray crystallography, quantum chemistry calculations, femtosecond transient absorption, and time-resolved fluorescence, as well as in long-term hydrogen production assays. Consistent with other recent reports, only systems containing halogenated chromophores were active for hydrogen production, as the long-lived triplet state is necessary for efficient bimolecular electron transfer. Here, it is shown that the photostability of the system improves with Bodipy dyes containing a mesityl group versus a phenyl group, which is attributed to increased electron donating character of the mesityl substituent. Unlike previous reports, the optimal ratio of chromophore to catalyst is established and shown to be 20:1, at which point this bimolecular dye/catalyst system performs 3–4 times better than similar chemically linked systems. We also show that the hydrogen production drops dramatically with excess catalyst concentration. The maximum turnover number of ∼700 (with respect to chromophore) is obtained under the following conditions: 1.0 × 10–4 M Co(dmgH)2pyCl, 5.0 × 10–6 M Bodipy dye with iodine and mesityl substituents, 1:1 v:v (10% aqueous TEOA):MeCN (adjusted to pH 7), and irradiation by light with λ > 410 nm for 30 h. This system, containing discrete chromophore and catalyst, is more active than similar linked Bodipy–Co(dmg)2 dyads recently published, which, in conjunction with our other measurements, suggests that the nominal dyads actually function bimolecularly.
Electropositive boron‐based substituent (phosphonium bora‐ylide) with an exceptionally strong π‐ and σ‐electron donating character dramatically increases the stability of a new type of N‐heterocyclic ...silylene 2 featuring amino‐ and bora‐ylide‐substituents. Moreover, the related silylium ion 4 and transition‐metal–silylene complexes, with trigonal‐planar geometries around the silicon center, are also well stabilized. Therefore, the N,B‐heterocyclic silylene 2 can be used as a strongly electron‐donating innocent ligand in coordination chemistry similarly to N‐heterocyclic carbenes.
Electron‐donating ligand: An electropositive boron‐based substituent (phosphonium bora‐ylide) with an exceptionally strong π‐ and σ‐electron donating character increases the stability of a new type of N‐heterocyclic silylene featuring amino and bora‐ylide substituents. It also efficiently stabilizes the related silylium ion and transition‐metal–silylene complexes even with a trigonal‐planar geometry around the silicon center.
Amidine is a notable nitrogen‐containing structural motif found in bioactive natural products and pharmaceuticals. Herein, a novel rhodium(I)‐catalyzed tandem reaction of readily accessible azides ...with isonitriles and boronic acids via a carbodiimide intermediate is achieved. This protocol offers an alternative approach toward N‐sulfonyl‐, N‐acyl‐, and N‐ phosphoryl‐functionalized, as well as general N‐aryl and N‐alkyl amidines with broad substrate scope. In addition, functionalized guanidines can also been synthesized when amines are used instead. The accomplishment of estrone‐derived amidine and glibenclamide bioisosteres further reveals the practical utility of this strategy.
In tandem: A rhodium(I)‐catalyzed tandem reaction of readily accessible azides with isonitriles and boronic acids via a carbodiimide intermediate offers an alternative approach towards N‐sulfonyl‐, N‐acyl‐, and N‐phosphoryl‐functionalized as well as general N‐aryl and N‐alkyl amidines with broad substrate scope. The synthesis of estrone‐derived amidine and glibenclamide bioisosteres reveals the practical utility of this strategy.
In this work, we report a facile method for preparing the B/N co-doped 2D porous carbon nanosheets (BNHCs) with high contents of boron (3.41–3.96 at.%) and nitrogen (5.1–6.09 at.%) via annealing the ...mixtures of ammonium humate and H3BO3. The ammonium humate is used as nitrogen-containing carbon precursor, and H3BO3 acts as boron source and pore-forming agent. Moreover, we demonstrate firstly that the existence of H3BO3 can enhance the graphitization degree of BNHCs by inducing the conversion of BCO2 to BC3 with increasing the H3BO3/ammonium humate mass ratio to 2. BNHC-1.5 exhibits the highest specific surface area of 592 m2 g−1 among all the samples, and BNHC-2 shows the enhanced graphitization degree and highest mesopore ratio (60.5%). In a three-electrode system, the BNHC-1, BNHC-1.5 and BNHC-2 exhibit high specific capacitances of 305 F g−1, 311 F g−1 and 225 F g−1 at 0.2 A g−1, and 64 F g−1, 125 F g−1 and 120 F g−1 at ultrahigh current density of 100 A g−1, respectively. Moreover, as assembled symmetric supercapacitor electrodes with high active material mass loading (∼180 μm, ∼13 mg cm−2), BNHCs deliver high specific capacitances of 170–210 F g−1 at 0.05 A g−1, and BNHC-2 presents an outstanding cyclic stability (94.8% capacitance retention after 10,000 cycles), making them promising candidates for practical supercapacitor application.
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∙B/N co-doped 2D porous carbon nanosheets (BNHCs) with high contents of boron (3.96 at.%) and nitrogen (6.09 at.%) are prepared by one-step carbonization of the mixtures of ammonium humate and H3BO3.∙The conversion of BCO2 to BC3 species can be induced via increasing the additive amount of H3BO3 even at relatively low temperature of 900 °C.∙The BNHCs supercapacitor electrodes exhibit high gravimetric capacitance, outstanding rate capability and cyclic stability with high mass loading (∼ 180 μm, ∼ 13 mg cm-2).
Tungsten tetraboride is an inexpensive, superhard material easily prepared at ambient pressure. Unfortunately, there are relatively few compounds in existence that crystallize in the same structure ...as tungsten tetraboride. Furthermore, the lack of data in the tetraboride phase space limits the discovery of any new superhard compounds that also possess high incompressibility and a three-dimensional boron network that withstands shear. Thus, the focus of the work here is to chemically probe the range of thermodynamically stable tetraboride compounds with respect to both the transition metal and the boron content. Tungsten tetraboride alloys with a variable concentration of boron were prepared by arc-melting and investigated for their mechanical properties and thermal stability. The purity and phase composition were confirmed by energy dispersive X-ray spectroscopy and powder X-ray diffraction. For variable boron WB x , it was found that samples prepared with a metal to boron ratio of 1:11.6 to 1:9 have similar hardness values (∼40 GPa at 0.49 N loading) as well as having a similar thermal oxidation temperature of ∼455 °C. A nearly single phase compound was successfully stabilized with tantalum and prepared with a nearly stoichiometric amount of boron (4.5) as W0.668Ta0.332B4.5. Therefore, the cost of production of WB4 can be decreased while maintaining its remarkable properties. Insights from this work will help design future compounds stable in the adaptable tungsten tetraboride structure.
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•Functionalized nanoporous graphene membranes could realize the removal of heavy metal ions.•Water permeation is correlated with the interfacial pore chemistry and confined ...structure.•Interfacial electrostatic interaction and ion dehydration effect cooperatively determine ion rejection.
Currently, elimination of heavy metal ions from contaminated water resource is an important issue in environmental protection. In this study, we simulated the separation performance of heavy metal ions using nanoporous graphene surfaces as reverse osmosis membranes with functionalized groups (boron, nitrogen and hydroxyl groups). We show these nanoporous graphenes could realize high water permeation and ion rejection for various conditions. The simulated water permeability is 2–5 orders of magnitude greater than that of currently commercial membranes. The interfacial water structures and flow velocity of water molecules within the nanopores were characterized. The calculations of the potential of mean force reveal water molecules generally face lower free energy barrier than ions when passing through graphene pores. The free energy barriers for ions can be explained as the combining contributions from the ion dehydration effect and the surface electrostatic interaction. Overall, the functionalized nanoporous graphene membranes exhibit potential application in the removal of heavy metal ions, and meanwhile our simulation results provide new insights into the ion rejection mechanism.
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