Ordered Mesoporous Crystalline Frameworks Toward Promising Energy Applications

Ordered mesoporous crystalline frameworks (MCFs), which possess both functional frameworks and well-defined porosity, receive considerable attention because of their unique properties including high surface areas, large pore sizes, tailored porous structures, and compositions. Construction of novel crystalline mesoporous architectures that allows for rich accessible active sites and efficient mass transfer is envisaged to offer ample opportunities for potential energy-related applications. In this review, the rational synthesis, unique structures, and energy applications of MCFs are the main focus. After summarizing the synthetic approaches, an emphasis is placed on the delicate control of crystallites, mesophases, and nano-architectures by concluding basic principles and showing representative examples. Afterward, the currently fabricated components of MCFs such as metals, metal oxides, metal sulfides, and metal-organic frameworks are described in sequence. Further, typical applications of MCFs in rechargeable batteries, supercapacitors, electrocatalysis, and photocatalysis are highlighted. This review ends with the possible development and synthetic challenges of MCFs as well as a future prospect for high-efficiency energy applications, which underscores a pathway for developing advanced materials.

Framework Uranyl Silicates: Crystal Chemistry and a New Route for the Synthesis

To date, uranyl silicates are mostly represented by minerals in nature. However, their synthetic counterparts can be used as ion exchange materials. A new approach for the synthesis of framework uranyl silicates is reported. The new compounds Rb₂[(UO₂)₂(Si₈O₁₉)](H₂O)_2.5 (1), (K,Rb)₂[(UO₂)(Si₁₀O₂₂)] (2), [Rb₃Cl][(UO₂)(Si₄O₁₀)] (3) and [Cs₃Cl][(UO₂)(Si₄O₁₀)] (4) were prepared at harsh conditions in "activated" silica tubes at 900 °C. The activation of silica was performed using 40% hydrofluoric acid and lead oxide. Crystal structures of new uranyl silicates were solved by direct methods and refined: 1 is orthorhombic, Cmce, a = 14.5795(2) Å, b = 14.2083(2) Å, c = 23.1412(4) Å, V = 4793.70(13) ų, R1 = 0.023; 2 is monoclinic, C2/m, a = 23.0027(8) Å, b = 8.0983(3) Å, c = 11.9736(4) Å, β = 90.372(3) °, V = 2230.43(14) ų, R1 = 0.034; 3 is orthorhombic, Imma, a = 15.2712(12) Å, b = 7.9647(8) Å, c = 12.4607(9) Å, V = 1515.6(2) ų, R1 = 0.035, 4 is orthorhombic, Imma, a = 15.4148(8) Å, b = 7.9229(4) Å, c = 13.0214(7) Å, V = 1590.30(14) ų, R1 = 0.020. Their framework crystal structures contain channels up to 11.62 × 10.54 Å filled by various alkali metals.

Encapsulation of halocadmate anion via hydrogen bonding: synthesis and characterization of bis(diethylenetriamine)cobalt(III) complex containing hexabromocadmate anion

In this work, the encapsulation of [CdBr6]4- by six cations, [Co(dien)2]3+ has been described with the help of single crystal X-ray structural study in the complex, mer-[Co(dien)2]2[CdBr6]Br2. The complex anion, [CdBr6]4- has been obtained through solution method while attempting to synthesize complex dianion, [CdBr4]2-. This newly synthesized complex has been initially characterized by elemental analyses and spectroscopic studies (IR, NMR and UV-Visible). IR and NMR studies have been used for the isomeric identification of [Co(dien)2]3+. Single crystal X-ray structure determination has revealed the presence of two complex cations, [Co(dien)2]3+, one complex anion, [CdBr6]4-, and two Br- anions. The complex has crystallized in monoclinic crystal system with space group, P21/n. The study of intermolecular interactions has confirmed the stability of crystal structure through N-H type H-bonding interactions besides electrostatic forces of attraction.

Exploring new belousovite-related zinc and cadmium alkali sulfate halides: synthesis and structural variability

Fourteen new belousovite-related compounds, AZn(TO₄)X (A = K, Rb, Cs, Tl, NH₄; T = S, Se; X = Cl, Br, I) have been prepared via melt and evaporation techniques by reacting AX and ZnTO₄ either at high temperatures or in hot aqueous solutions. They adopt the layered structure of the belousovite archetype, and constitute a morphotropic series. The apophyllite-type layers in these structures undergo different corrugations, most pronounced in the case of CsZn(SO₄)I. In addition, during the study two species unrelated to belousovite, namely Na₄Zn(SO₄)₂Cl₂ and Cs₂Cd₃(SO₄)₄, were found with framework crystal structures having different topology and belonging to new structure types.

Recent Advances in the Synthesis of Inorganic Materials Using Environmentally Friendly Media

Deep Eutectic Solvents have gained a lot of attention in the last few years because of their vast applicability in a large number of technological processes, the simplicity of their preparation and their high biocompatibility and harmlessness. One of the fields where DES prove to be particularly valuable is the synthesis and modification of inorganic materials-in particular, nanoparticles. In this field, the inherent structural inhomogeneity of DES results in a marked templating effect, which has led to an increasing number of studies focusing on exploiting these new reaction media to prepare nanomaterials. This review aims to provide a summary of the numerous and most recent achievements made in this area, reporting several examples of the newest mixtures obtained by mixing molecules originating from natural feedstocks, as well as linking them to the more consolidated methods that use "classical" DES, such as reline.

"Soft" Alkali Bromide and Iodide Fluxes for Crystal Growth

In this review we discuss general trends in the use of alkali bromide and iodide (ABI) fluxes for exploratory crystal growth. The ABI fluxes are ionic solution fluxes at moderate to high temperatures, 207 to ~1,300°C, which offer a good degree of flexibility in the selection of the temperature profile and solubility. Although their main use is to dissolve and recrystallize "soft" species such as chalcogenides, many compositions with "hard" anions, including oxides and nitrides, have been obtained from the ABI fluxes, highlighting their unique versatility. ABI fluxes can serve to provide a reaction and crystallization medium for different types of starting materials, mostly the elemental and binary compounds. As the use of alkali halide fluxes creates an excess of the alkali cations, these fluxes are often reactive, incorporating one of its components to the final compositions, although some examples of non-reactive ABI fluxes are known.

Borosulfates-Synthesis and Structural Chemistry of Silicate Analogue Compounds

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 H[B(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.

Synthesis and Physical Property Characterisation of Spheroidal and Cuboidal Nuclear Waste Simulant Dispersions

This study investigated dispersions analogous to highly active nuclear waste, formed from the reprocessing of Spent Nuclear Fuel (SNF). Non-radioactive simulants of spheroidal caesium phosphomolybdate (CPM) and cuboidal zirconium molybdate (ZM-a) were successfully synthesised; confirmed via Scanning Electron Microscopy (SEM), powder X-ray diffraction (PXRD) and Fourier transform infrared (FTIR) spectroscopy. In addition, a supplied ZM (ZM-b) with a rod-like/wheatsheaf morphology was also analysed along with titanium dioxide (TiO₂). The simulants underwent thermal gravimetric analysis (TGA) and size analysis, where CPM was found to have a D50 value of 300 nm and a chemical formula of Cs₃PMo₁₂O₄₀·13H₂O, ZM-a a D50 value of 10 μm and a chemical formula of ZrMo₂O₇(OH)₂·3H₂O and ZM-b to have a D50 value of 14 μm and a chemical formula of ZrMo₂O₇(OH)₂·4H₂O. The synthesis of CPM was tracked via Ultraviolet-visible (UV-Vis) spectroscopy at both 25 °C and 50 °C, where the reaction was found to be first order with the rate constant highly temperature dependent. The morphology change from spheroidal CPM to cuboidal ZM-a was tracked via SEM, reporting to take 10 days. For the onward processing and immobilisation of these waste dispersions, centrifugal analysis was utilised to understand their settling behaviours, in both aqueous and 2 M nitric acid environments (mimicking current storage conditions). Spheroidal CPM was present in both conditions as agglomerated clusters, with relatively high settling rates. Conversely, the ZM were found to be stable in water, where their settling rate exponents were related to the morphology. In acid, the high effective electrolyte resulted in agglomeration and faster sedimentation.

Nickel(I) Aryl Species: Synthesis, Properties, and Catalytic Activity

In this work, Ni(I) aryl species that are directly relevant to cross-coupling have been synthesized. Transmetalation of (dppf)Ni^IX (dppf = 1,1'-bis(diphenylphosphino)-ferrocene, X = Cl, Br) with aryl Grignard reagents or aryl boronic acids in the presence of base produces Ni(I) aryl species of the form (dppf)Ni^I(Ar) (Ar = Ph, o-tolyl, 2,6-xylyl, 2,4,6-mesityl, 2,4,6-ⁱPr₃C₆H₂). The stability of the Ni(I) aryl species is inversely correlated to the steric bulk on the aryl ligand. The most unstable Ni(I) aryl species are the most active precatalysts for Suzuki-Miyaura reactions because they rapidly decompose to generate the active Ni(0) catalyst. This study shows that Ni(I) aryl species are initially formed in the activation of Ni(I) halide precatalysts for Suzuki-Miyaura reactions and establishes their stoichiometric and catalytic reactivity profile.

Synthesis and Characterization of Tungsten Nitrido Amido Guanidinato Complexes as Precursors for Chemical Vapor Deposition of WNxCy Thin Films

Tungsten nitrido amido guanidinato complexes of the type WN(NR₂)[(NR')₂C(NR₂)]₂ (R = Me, Et_; R' = ⁱ Pr, Cy) were synthesized as precursors for aerosol-assisted chemical vapor deposition (AACVD) of WN_xC_y thin films. The reaction of tungsten nitrido amido complexes of the type WN(NR₂)₃ (R = Me, Et) with two equivalents of a carbodiimide R'N=C=NR' (R' = ⁱ Pr, Cy) resulted in two insertions of a carbodiimide into W-N(amido) bonds, affording bis(guanidinato) amido nitrido tungsten complexes. These compounds were characterized by ¹⁴N NMR, indicating distinctive chemical shifts for each type of N-bound ligand. Crystallographic structure determination of WN(NMe₂)[(N ⁱ Pr)₂C(NMe₂)]₂ showed the guanidinato ligands to be non-equivalent. The complex WN(NMe₂)[(N ⁱ Pr)₂C(NMe₂)]₂ was demonstrated to serve as a precursor for AACVD of WN_xC_y thin films, resulting in featureless, X-ray amorphous thin films for growth temperatures 200 - 400 °C.

Effects of Pr₆O11 Addition on the Acid Resistance of Ceramic Proppant

This paper investigated the effect of Pr₆O₁₁ addition on the acid resistance of ceramic proppant. Acid resistance of proppants can be improved by introducing Pr₆O₁₁ into the Al₂O₃-CaO-MgO-SiO₂ (ACMS) system. To illustrate and explain the mechanism of acid resistance, the samples were characterized by different techniques, using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The phase structure of the specimens was characterized by XRD and SEM-detected microstructures of the specimens. It was observed that with the increase of rare-earth oxide content, the acid solubility of the specimens decreased, and then increased when it reached the minimum value 0.45 wt %. The results of the research show that the improvement of acid resistance with rare-earth oxides was achieved by refining the grain size, strengthening the grain boundary, and turning Ca₂Al₂SiO₇, in which acid resistance is poor, into CaAl₁₂O₁₉, which possesses better acid resistance, and then enhance the acid resistance of the proppants. Furthermore, Pr₆O₁₁ can form a solid solution with Ca₂Al₂SiO₇ and CaAl₁₂O₁₉. The acid resistance of CaAl₁₂O₁₉ improves with the increase of solid solubility. In contrast, the acid resistance of Ca₂Al₂SiO₇ will decrease after Ca₂Al₂SiO₇ forms a solid solution with Pr₆O₁₁.

Synthesis of Cerite

Some compounds isostructural with cerite have been synthesized hydrothermally at temperatures from 500 to 720 °C. The compositional range for cerite, and its phase relation to the silicate apatites are established in terms of ionic radii of rare-earth and divalent ions. The proposed formula for cerite on the basis of isomorphism with whitlockite, Ca₃(PO₄)₂, is discussed. A solid-solution series between Ca₉P₆O₂₄ - Ca₇Mg₂P₆O₂₄ (whitlockite - Mg-whitlockite) has been established.