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The review presents data on the synthesis, structure, reactivity, and catalytic activity of alkyl derivatives of rare earth metals in the oxidation state +2 (Sm, Eu, Yb) and their analogues containing heavy alkaline earth metals (Ca, Sr, Ba). The synthetic aspects and structural features of this unique class of organometallic compounds, which contain highly reactive M–C bonds, including alkyl, α-silylmethyl, and also benzyl, diphenylmethyl, and triphenylmethyl derivatives are considered. The bibliography includes 157 references.

To improve the removal capacity of NO + O2 effectively, the alkaline earth metal-doped order mesoporous carbon (A-C-FDU-15(0.001) (A = Mg, Ca, Sr and Ba)) and Mg-C-FDU-15(x) (x = 0.001−0.003) samples were prepared, and their physicochemical and NO + O2 adsorption properties were determined by means of various techniques. The results show that the sequence in (NO + O2) adsorption performance was as follows: Mg-C-FDU-15(0.001) (93.2 mg/g) > Ca-C-FDU-15(0.001) (82.2 mg/g) > Sr-C-FDU-15(0.001) (76.1 mg/g) > Ba-C-FDU-15(0.001) (72.9 mg/g) > C-FDU-15 (67.1 mg/g). Among all of the A-C-FDU-15(0.001) samples, Mg-C-FDU-15(0.001) possessed the highest (NO + O2) adsorption capacity (106.2 mg/g). The species of alkaline earth metals and basic sites were important factors determining the adsorption of NO + O2 on the A-C-FDU-15(x) samples, and (NO + O2) adsorption on the samples was mainly chemical adsorption. Combined with the results of (NO + O2)-temperature-programmed desorption ((NO + O2)-TPD) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) characterization, we deduced that there were two main pathways of (NO + O2) adsorption: one was first the conversion of NO and O2 to NO2 and then part of NO2 was converted to NO2− and NO3−; and the other was the direct oxidation of NO to NO2− and NO3−.

The article is devoted to the problems of aluminate solutions sorption purification from harmful organic impurities in the production of alumina from the Bayer experiment. The study of sorption of basic classes of organic impurities isolated from industrial aluminate solutions showed that magnesium and calcium hydrocarboaluminates have a high selectivity in relation to the most harmful classes of organic substances for the process. The results of the sorption process kinetics and thermodynamics studies are given, optimal technological parameters of sorption purification and conditions for the synthesis of active sorbents from alkaline aluminate solutions and activated magnesium and calcium raw materials are determined.

Since the Fukushima plant accident took place in 2011, a large amount of radioactive cesium ions have been released and their separation from wastewater has been a major concern. Herein, we have synthesized a Cs-137 adsorbent: calcium-doped Prussian Blue (Ca-PB), using a simple solution co-precipitation technique. The adsorbent was characterized by FTIR and XRD, and systematically evaluated the kinetics and adsorption equilibrium for Cs+ adsorbed to Ca-PB. The experimental data were followed by a pseudo-second order kinetic model and well adapted to Langmuir’s isothermal model. The research showed that Ca-PB can be used to treat water contaminated by Cs-137 in extremely acidic conditions.

Orthocarbonates of alkaline earth metals are the newly discovered class of compounds stabilized at high pressures. Mg-orthocarbonates are the potential carbon host phases, transferring oxidized car...

The promotion of BiOBr via simultaneous alkaline earth metal (Ba) doping and massive oxygen vacancies (OVs) was for the first time investigated toward the photocatalytic removal of NO in air. The a...

The understanding of thermal behaviors of inherent alkali and alkaline earth metals (AAEMs) is significant for the reduction of corrosion and deposition and further utilization of by-products. In t...

In order to evaluate the slagging characteristics of lignite with high alkali and alkaline earth metal (AAEM) content under different atmospheres, three Xinjiang coals with similar AAEM compositions and various silica/alumina ratio (RS/A) were used as fuels in this study, namely, QiYa1 coal (QY1c), QiYa2 coal (QY2c), and YiHua coal (YHc). The experiments were carried in a horizontal tube furnace system, and 3 atm of CO2, CO/CO2, and H2O (g) were used to simulate gasification conditions in different parts of the boilers. Other than the characterization of samples, pseudo ternary phase diagrams and the thermodynamic modeling of ash melting behaviors were calculated using FactSage 7.2. Accordingly, the results demonstrated that the higher the RS/A, the wider the distribution of the low-temperature region in the phase diagrams. Moreover, increasing the relative content of CaO was found to increase the ash melting temperatures of QY1c and QY2c. The proportion of the liquid phase QY1c and QY2c ashes in the CO/CO2 atmosphere was observed to be much higher than that of CO2 and H2O (g) in a typical circulating fluidized bed (CFB) gasification temperature interval, while the generation of liquid phase YHc ash was less affected by the atmospheres. Additionally, the H2O (g) atmosphere was found to promote the release of Na during the gasification process. Under the same atmosphere, coal with a higher RS/A may more strongly capture Na-based species. The bottom of boilers was observed to be the most severe slagging zone, and purging with H2O (g) served as a good method in alleviating the low-temperature slagging of the return feeder.

Ion-exchange modeling is used widely to describe and predict ion-adsorption data on clay minerals. Although the model parameters are usually optimized by curve fitting experimental data, this approach does not confirm the identity of the adsorption sites. The purpose of the present study was to extend to divalent cations a previous study on the retention of monovalent cations on Na-saturated montmorillonite (NaMnt) which optimized some of the model parameters using density functional theory (DFT) simulations. The adsorption strength of divalent cations increased in the order Mg2+ < Cd2+ < Ca2+ < Sr2+ < Ba2+. After adding adsorption of metal hydroxide species (MOH+), the three-site ion-exchange model was able to describe adsorption data over a wide pH range (pH 1–10) on NaMnt. X-ray diffraction (XRD) analyses were conducted to investigate the interlayer dimension of clay samples under various conditions. The cation retention strengths of divalent cations did not correlate with interlayer dimensions. The XRD analyses of the Mnt showed a d001 value of 19.6 A when saturated with alkaline earth cations, 22.1 A with Cd2+, 15.6 A with Na+, and 15.2 A with H+. In the case of Na+, the 15.6 A peak decreased gradually and disappeared, and new peaks at 22.1 and 19.6 A appeared when the percentages of Mg2+ and Ba2+ adsorbed increased on NaMnt. The peak shifted from 22.1 to 20.3 and 19.6 A when the pH increased for all cations except Cd2+, which stayed constant at 22.1 A. The coexistence of multiple d001 peaks in the XRD patterns suggested that the interlayer cations were segregated, and that the interlayer ion–ion interactions among different types of ions were minimized.

Alkaline earth metal salts of chiral bis-sulfonimide were prepared in this study. Asymmetric Diels-Alder reactions catalyzed by these metal salts were examined to evaluate the performance of bis-su...

The present work shows results of studying acid-base properties of the surface by the methods of pH-metry and Hammett of amorphous silicon dioxide from rice husks and straw obtained by various schemes: oxidative firing; oxidative roasting with preliminary treatment with 0.1 M hydrochloric acid solution; precipitation from alkaline solutions. The samples obtained by the thermal method contain impurities of alkali, alkaline earth metals, aluminum, and aluminum and practically do not contain water. The composition of the deposited samples contains a small fraction of impurities (0.05%) and water - from 8.2 to 10.2%. The pH value of an aqueous suspension of silicon dioxide has a neutral, alkaline or acidic environment depending on the content of impurities of alkali and alkaline earth metals. Distribution of acid-base centers on the surface of the samples is nonmonotonic and heterogeneous, and manifests itself in discreteness with a fairly clear differentiation of sorption bands with maxima of different intensities corresponding to a certain pKa value. Distribution curves of the adsorption centers of the indicators on the surface of the samples of amorphous silicon dioxide are similar to each other. There are four types of active centers on their surface: acidic Lewis (pKa + 16.80), Bransted main (pKa +7.15 and +9.45) and acid (pKa + 2.50). The number of active centers depends on the preparation scheme and is determined by the content of impurity elements and water in the oxide samples.

Magnesium (Mg) is a cheap, non-toxic, and recyclable alkaline earth metal that constitutes about 2% weight in the Earth’s crust. The use of magnesium catalysts to forge chiral moieties in molecules is highly attractive. Based on our work in recent years, we describe the current progress in the development of in situ generated magnesium catalysts and their application in asymmetric synthesis. In this perspective, a critically concise classification of in situ generated magnesium catalytic modes, with relevant examples, is presented, and representative mechanisms of each category are discussed. Building on the established diverse strategies, one can foresee that more innovative and structurally creative magnesium catalysts that are generated in situ will be developed to overcome more formidable challenges of catalytic enantioselective reactions.1 Introduction2 Magnesium Catalysts Generated in Situ from Chiral Ligands Containing Dual Reactive Hydrogens3 Magnesium Catalysts Generated in Situ from Monoanionic Chiral Ligands4 Bimetallic and Polymetallic Magnesium Catalysts Assembled in Situ5 Summary and Outlook

In this study, the oxidation behavior of Cu alloys containing two alkaline earth metals (i.e., Mg and Ca) at 500 °C was investigated. The Mg+Mg2Ca master alloy was used for the simultaneous addition of Mg and Ca into Cu. As a result of the oxidation test, all examined samples showed weight gains that followed parabolic laws. Mg addition in Cu considerably slowed down the oxidation rate, while the use of the Mg+Mg2Ca master alloy as an alloying element for Mg led to an even further reduction in the oxidation rates at the testing temperature. The phase diagrams with the oxygen partial pressure showed that the Ca and Mg-containing alloy resulted in the formation of CaO as the primary oxide and MgO as the secondary oxide. The improved oxidation resistance can be attributed to the mixed surface layer of CaO and MgO, which control the growth rate of Cu2O.

Complex oxides with pronounced proton transfer occupy a special place in modern solid-state ionics and high-temperature electrochemistry, being of great interest from both fundamental and applied viewpoints. Doped barium cerate-zirconates (BaCeO3–BaZrO3) are positioned as the most conductive oxides, and therefore they are widely used in various solid oxide devices. However, the presence of a highly basic alkaline earth cation leads to an insufficient chemical stability of cerate-zirconates in real working conditions. In this regard, designing new proton-conducting oxides with improved chemical stability is an actual issue. Some lanthanum-containing perovskites, LaBO3 (where B is a trivalent element), can be considered as stable analogs since they contain no alkaline and alkaline earth elements in their basic structures. This review aims at a critical analysis of the properties of these compounds and the prospects for their application as electrolyte membranes for solid oxide fuel cells, pumps, and sensors. The paper provides basic information about LaBO3-based compounds, highlights their advantages in comparison with other representatives of proton conductors, and indicates disadvantages acting as limiting factors for the application of lanthanum-containing protonic electrolytes with a perovskite structure in electrochemical devices.

Two new alkali/alkali earth metal and d10 transition metal mixed cyanurate birefringent crystals, Li2Zn2(H2C3N3O3)2(HC3N3O3)(OH)2·2H2O (I) and BaZn2(H2C3N3O3)2(HC3N3O3)(OH)2·2H2O (II), were synthes...

The pyrolysis characteristics including reaction kinetics and products distribution of cellulose pyrolysis in the presence of AAEM oxalates were preliminarily studied by using the TG and PY-GC/MS analysis. In general, the main mass loss region took place at 300–400 °C and the maximum mass loss temperature was about 380 °C. The activation energy Ea of cellulose pyrolysis (159 kJ/mol) was decreased in the presence of AAEM oxalates (K2C2O4—123 kJ/mol, MgC2O4—151 kJ/mol and CaC2O4—138 kJ/mol). The major pyrolytic components were classified into furans, anhydrosugars, acids, esters, alcohols, aldehydes, pyrans, ketones, hydrocarbons and phenols, etc. The presence of AAEM oxalates promoted the generation of ketones. In particular, K2C2O4 and MgC2O4 showed a high selectivity (relative content: > 30%) on the production of ketones. As a good candidate of MgO, MgC2O4 or MgCO3 has a high potential for both gas upgrading and porous carbon production in biomass pyrolysis.

We study the structure, crystallization, and performances of the sealing glasses with the composition (mol.%) of 12Al2O3·8B2O3·40SiO2·40RO (R = Mg, Ca, Sr) for solid oxide fuel cells (SOFCs) before and after isothermal treatment at 700°C, which is within the operation temperature range (600-800°C) of SOFCs. The crystallization behavior has been investigated by differential scanning calorimetry and X-ray diffraction under both dynamic and isothermal conditions. The structural evolution is probed using the Raman and nuclear magnetic resonance spectroscopies. The performances of the sealing glasses are characterized in terms of the coefficient of thermal expansion, the crystallization-induced stress at glass–steel interface. We find that strong crystallization occurs at the operation temperature (700°C) far below the crystallization onset temperature measured by DSC. The structure origin of this anomalous crystallization is discussed in terms of structural heterogeneity of the three studied glasses. We determine the residual stress at the interface between the Ca-containing glass and the steel after isothermal treatment at 700°C for 48 h, but this stress does not lead to falling off the glass layer from the steel. This indicates that this glass is a good candidate to be applied in SOFCs.

Previous studies of the effect of IL cation/anion hydrophobicity and the nature of the aqueous phase anion on the partitioning of alkali and alkaline earth cations between an acidic aqueous phase a...

Alkaline earth vanadates (Ae–V: Ae = Ca, Sr, and Ba) were supported on mesoporous SiO2 by a wet impregnation method. The catalytic activity of the prepared materials for the decomposition of SO3 in...

Tetrahedra-based nitrides with network structures have emerged as versatile materials with a broad spectrum of properties and applications. Both nitridosilicates and nitridophosphates are well-known examples of such nitrides that upon doping with Eu2+ exhibit intriguing luminescence properties, which makes them attractive for applications. Nitridosilicates and nitridophosphates show manifold structural variability; however, no mixed nitridosilicatephosphates except SiPN3 and SiP2N4NH have been described so far. The compounds AESiP3 N7 (AE=Sr, Ba) were synthesized by a high-pressure high-temperature approach using the multianvil technique (8 GPa, 1400-1700 °C) starting from the respective alkaline earth azides and the binary nitrides P3 N5 and Si3 N4 . The latter were activated by NH4 F, probably acting as a mineralizing agent. SrSiP3 N7 and BaSiP3 N7 were obtained as single crystals. They crystallized in the barylite-1O (M=Sr) and barylite-2O structure types (M=Ba), respectively, with P and Si being occupationally disordered. Cation disorder was further supported by solid-state NMR spectroscopy and energy-dispersive X-ray spectroscopy (EDX) mapping of BaSiP3 N7 with atomic resolution. Upon doping with Eu2+ , both compounds showed blue emission under UV excitation.

Raman spectroscopy is used to study the molecular relaxation processes in the following alkaline earth metal nitrates: Ca(NO3)2, Sr(NO3)2, and Ba(NO3)2. The first-order crystal–melt phase transition in calcium, strontium and barium nitrates is found to be extended. A premelting region is revealed in these alkaline earth metal nitrates. Premelting phenomena are shown to manifest themselves in the temperature dependences of spectral parameters.

Zhundong high-alkali coal has been studied a lot owing to its abundant reserve but serious ash-related issues. Oxy-fuel combustion profits the reduction of pollutant emissions and coal blending alleviates the ash-related problems practically. Nevertheless, little work if any has been carried out on oxy-fuel co-combustion of Zhundong coal, while the influences of blending on the migration of iron and alkali alkaline-earth metals have yet to be adequately understood. This study aims to illuminate the release and migration behaviors of alkali alkaline-earth metals, iron and aluminum in oxy-fuel co-combustion via a lab-scale experimental system. Experimental results showed that the yield, color, bulk, and composition of ash were greatly temperature-dependent and significantly affected by the blending ratio in oxy-fuel co-combustion. As the blending ratio was 50%, the transformation and release features of iron, sodium and calcium in the blend with combustion temperature were close to those of non-Zhundong coal. The blending of Lingxin coal into Zhundong coal could benefit the transformation from NH4Ac-soluble calcium to H2O-soluble form, and facilitate the transformation of HCl-soluble aluminum and iron to insoluble form. The occurrence modes of elements and the ash yield of individual coal both exerted profound impacts on the element release ratio and chemical forms within ash of the blends. The present research has potential to offer an improved knowledge on the functional mechanisms of alkali alkaline-earth metals, aluminum, and iron on ash-related issues during high-alkali coal oxy-fuel co-combustion.

The distillation of chlorides from their molten mixtures is experimentally studied under various conditions. In all cases, the dilute solutions of BaCl2, SrCl2, and NdCl3 (1–2 mol % each), as representatives of alkaline, alkaline earth, and rare earth metal chlorides, in the molten LiCl–KCl eutectic mixture are subjected to evaporation at a low pressure (down to ~1 Pa) and a temperature of 753–1033°C. The sublimate and salt melt compositions before and after distillation are analyzed, and conclusions are drawn about the degree of distillation, the selectivity of evaporation of the molten mixture components, and the relative volatilities of various chlorides.

Morphology-controlled strontianite nanostructures have attracted interest in various fields, such as electrocatalyst and photocatalysts. Basic additives in aqueous strontium solutions is commonly used in controlling strontianite nanostructures. Here, we show that trace water also serves an important role in forming and structuring vertically oriented strontianite nanorod arrays on strontium compounds. Using in situ Raman spectroscopy, we monitored the structural evolution from hydrated strontium to strontianite nanorods, demonstrating the epitaxial growth by vapor–liquid–solid mechanism. Water molecules cause not only the exsolution of Sr liquid droplets on the surface but also the uptake of airborne CO2 followed by its ionization to CO32−. The existence of intermediate SrHO+–OCO22− phase indicates the interaction of CO32− with SrOH+ in Sr(OH)x(H2O)y cluster to orient strontianite crystals. X-ray diffraction simulation and transmission electron microscopy identify the preferred-orientation plane of the 1D nanostructures as the (002) plane, i.e., the growth along the c-axis. The anisotropic growth habit is found to be affected by the kinetics of carbonation. This study paves the way for designing and developing 1D architecture of alkaline earth metal carbonates by a simple method without external additives at room temperature.

High temperature (up to 1873K) oxy-fuel combustion experiments were conducted on a fixed-bed reactor. Two combustion modes were designed: coupled combustion (volatile combustion and char combustion are simultaneous) and separated combustion (volatile combustion and char combustion are separated and individual). Bases on it, effect of alkali and alkali earth metals (AAEMs) and transition metals (TMs) in coal ash on the fuel-NO release characteristics was studied. Results show that in the coupled combustion, AAEMs accelerate the fuel-NO release rate. Besides, AAEMs decreased fuel-NO release amount by around 10% at different temperatures. This inhibition effect is related to activity of metal elements. The effect of TMs is sensitive to temperature. Mn promotes the oxidation of fuel-N intensively at lower temperature, while Fe and Cu can improve the fuel-NO reduction efficiency at higher temperature. Coal ash is beneficial to NO reduction and the reduction efficiency is higher than 50% at 1873K. In the separated combustion, Mg, Ca and Mn have almost no effect on volatile-NO and char-NO release. Na and K can decrease the volatile-NO and char-NO release amount below 1573K. Both volatile-NO and char-NO reduction efficiency of K and Na decreases from 20% to 0% as temperature rises. Fe and Cu can suppress the release of volatile-NO and char-NO. The volatile-NO reduction efficiency of Fe and Cu increases but the char-NO reduction efficiency decreases with temperature increasing. Coal ash can improve the proportion of volatile-NO in fuel-NO, about 25% at 1573K. At last, the potential catalytic mechanisms in coupled and separated combustion were proposed.

The synthesis and structural characterization of Ae(TpiPr2)2 (Ae = Mg, Ca, Sr, Ba; TpiPr2 = hydrido-tris(3,5-diisopropyl-pyrazol-1-yl)borate) are reported. In the crystalline state, the alkaline earth metal centers are six-coordinate, even the small Mg2+ ion, with two κ3-N,N',N''-TpiPr2 ligands, disposed in a bent arrangement (B···Ae···B < 180°). However, contrary to the analogous Ln(TpiPr2)2 (Ln = Sm, Eu, Tm, Yb) compounds, which all exhibit a bent-metallocene structure close to Cs symmetry, the Ae(TpiPr2)2 compounds exhibit a greater structural variation. The smallest Mg(TpiPr2)2 has crystallographically imposed C2 symmetry, requiring both bending and twisting of the two TpiPr2 ligands, while with the similarly sized Ca2+ and Sr2+, the structures are back toward the bent-metallocene Cs symmetry. Despite the structural variations, the B···M···B bending angle follows a linear size-dependence for all divalent metal ions going from Mg2+ to Sm2+, decreasing with increasing metal ion size. The complex of the largest metal ion, Ba2+, forms an almost linear structure, B···Ba···B 167.5°. However, the "linearity" is not due to the compound approaching the linear metallocene-like geometry, but is the result of the pyrazolyl groups significantly tipping toward the metal center, approaching "side-on" coordination. An attempt to rationalize the observed structural variations is made.

Thermodynamic data for radium for radioactive waste management have been predicted using an electrostatic model and correlation with the ionic radii of the alkaline earth metals. Estimation of the standard Gibbs free energy of formation and standard molar entropy of aqueous radium species and compounds has been based on such approaches as extrapolation of the thermodynamic properties of strontium and barium, and use of a model of ion pair formation. The predicted thermodynamic data for radium have been compared with previously reported values.

Ba2BS3Cl and Ba5B2S8Cl2 have been synthesized by using PbCl2 as the flux and source of halogen. The two compounds show 3D network structures built by isolated [BS3] units with different Ba–S–Cl groups. This work enriches the structural diversity of boron chemistry and provides an insight into the synthesis of thioborates.

Multi-nitrogen or polynitrogen compounds can be used as potential high energy-density materials, so they have attracted great attention. Nitrogen can exist in alkaline earth metal nitrogen-rich (N-rich) compounds in the form of single or double bonds. In recent years, to explore N-rich compounds which are stable and easy to synthesize has become a new research direction. The N-rich compounds XN6 (X = Ca, Sr and Ba) have been reported under normal pressure. In order to find other stable crystal structures, we have performed XN6 (X = Ca, Sr and Ba) exploration under high pressure. We found that SrN6 has a new P phase at a pressure of 22 GPa and an infinite nitrogen chain structure, and BaN6 has a new C2/m phase at 110 GPa, with an N6 ring network structure. Further, we observed that the infinite nitrogen chain and the N6 ring network structure contain typical covalent bonds formed by the hybridization of the sp2 and sp3 orbitals of N, respectively. It is found that both SrN6 and BaN6 are semiconductor materials and the N-2p orbital plays an important role in the stability of the crystal structure for P-SrN6 and C2/m-BaN6. Because of the polymerization of nitrogen in the two compounds and their stabilities under high pressure, they can be used as potential high energy-density materials. The research in this paper further promotes the understanding of alkaline earth metal N-rich compounds and provides new information and methods for the synthesis of alkaline earth metal N-rich compounds (XN6, X = Ca, Sr and Ba).

Understanding the corrosion behavior of glasses in near-neutral environments is crucial for many technologies including glasses for regenerative medicine and nuclear waste immobilization. To maintain consistent pH values throughout experiments in the pH = 7 to 9 regime, buffer solutions containing tris(hydroxymethyl)aminomethane (“Tris”, or sometimes called THAM) are recommended in ISO standards 10993-14 and 23317 for evaluating biomaterial degradation and utilized throughout glass dissolution behavior literature—a key advantage being the absence of dissolved alkali/alkaline earth cations (i.e. Na+ or Ca2+) that can convolute experimental results due to solution feedback effects. Although Tris is effective at maintaining the solution pH, it has presented concerns due to the adverse artificial effects it produces while studying glass corrosion, especially in borosilicate glasses. Therefore, many open questions still remain on the topic of borosilicate glass interaction with Tris-based solutions. We have approached this topic by studying the dissolution behavior of a sodium borosilicate glass in a wide range of Tris-based solutions at 65 °C with varied acid identity (Tris–HCl vs. Tris–HNO3), buffer concentration (0.01 M to 0.5 M), and pH (7–9). The results have been discussed in reference to previous studies on this topic and the following conclusions have been made: (i) acid identity in Tris-based solutions does not exhibit a significant impact on the dissolution behavior of borosilicate glasses, (ii) ∼0.1 M Tris-based solutions are ideal for maintaining solution pH in the absence of obvious undesirable solution chemistry effects, and (iii) Tris–boron complexes can form in solution as a result of glass dissolution processes. The complex formation, however, exhibits a distinct temperature-dependence, and requires further study to uncover the precise mechanisms by which Tris-based solutions impact borosilicate glass dissolution behavior.

We predicted the stable alkaline earth complexes M(Cp)3− (M = Ca, Sr, Ba; Cp = cyclopentadienyl), where the M centers were in their stable +2 oxidation state and mimicked the bonding behaviour of transition metals by participating in bonding with the π orbitals of Cp ligands using their d orbitals.

The high-pressure structures of alkaline earth metal hydride-fluorides (AHFs) (A = Ca, Sr, Ba) were investigated up to 8 GPa. While AHF adopts the fluorite-type structure (Fm3[combining macron]m) at ambient pressure without anion ordering, the PbCl2-type (cotunnite-type) structure (Pnma) is formed by pressurization, with a declining trend of critical pressure as the ionic radius of the A2+ cation increases. In contrast to PbCl2-type LaHO and LaOF whose anions are fully ordered, the H-/F- anions in the high-pressure polymorph of SrHF and BaHF are partially ordered, with a preferential occupation of H- at the square-pyramidal site (vs. tetrahedral site). First-principles calculations partially support the preferential anion occupation and suggest occupation switching at higher pressure. These results provide a strategy for controlling the anion ordering and local structure in mixed-anion compounds.

Exploration of novel molecular switches is an ongoing hot issue in molecular electronics. Alkalides and electrides are two typical representatives of excess electron compounds. It was found that M(HF)3M (M = Li or Na) induced by an oriented external electric field are good candidates for inorganic multi-response nonlinear optical (NLO) molecular switches. Their off forms (C3h) exhibit electride-like super alkali earth atom characteristics, while their on forms (C3v) exhibit charming superalkalide (M = Na or Li) or superalkali electride characteristics (M = Li). The increases of the static first hyperpolarizabilities (βe0) from off to on forms constitute a 2–3 orders of magnitude improvement for both M = Li and Na. These extremely large differences in βe0 reinforce the potential of M(HF)3M for applications in excellent multi-response nonlinear optical materials.

Co-pyrolysis of two different types of biomass among apple tree branch (ATB), knotweed stem (KWS), seaweed (SW) and rice straw (RSt) was conducted to obtain co-pyrolysis char (co-char), and then the steam gasification of those co-chars was compared with the steam co-gasification of the physically mixed individual biochars to investigate the synergetic effect resulted from alkali and alkali earth metal (AAEM) in each biomass involved. It is found that the silica species in the RSt had negative effect on the activity of co-char due to the formation of alkali silicate compounds. However, combination of RSt with some non-woody biomass such as SW also showed promoting effect. In particular, the gasification of the co-char from the combination of various biomass with low or no silica content showed improved gasification efficiencies due to the synergetic effect AAEM species in the co-char from the different biomass. Therefore, the biomass selection should play a significant role in the co-pyrolysis of different biomass in the two-stage gasification system.

Surface and bulk structure modification is an effective strategy to improve the photocatalytic performance of g-C3N4 (CN). In this work, dilute NaOH solution was used in situ to regulate the CN structure for enhanced photocatalytic hydrogen evolution reaction (HER). Characterization results indicate that after treatment with dilute NaOH solution, the surface of CN was hydroxylated, resulting in the change of CN structure and the increase of BET specific surface area. Furthermore, some Na+ ions can be intercalated into the framework of CN, and form the Na–N bond. These modifications boost the HER activity of CN. The test carried out in 7.5 mM NaOH solution shows the highest activity and it is almost 3.7 times higher than that performed in water. Control tests indicate that hydroxides of other alkali and alkali earth metals such as LiOH, KOH, Ca(OH)2, and Ba(OH)2 have similar promotion effects. This work demonstrates a valid and simple way to enhance the HER activity of CN through performing the reaction in a weakly alkaline solution.

The production of syngas via dry reforming of methane (DRM) has drawn tremendous research interest, ascribed to its remarkable economic and environmental impacts. Herein, we report the synthesis of K, Na, Cs, Li, and Mg-promoted Ni/La2O3 using solution combustion synthesis (SCS). The properties of the catalysts were determined by N2 physisorption experiments, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), and H2-TPR (temperature programmed reduction). In addition, their catalytic performance towards DRM was evaluated at 700 °C. The results demonstrated that all catalysts exhibited porous structures with high specific surface area, in particular, Mg-promoted Ni/La2O3 (Mg–Ni–La2O3) which depicted the highest surface area and highest pore volume (54.2 m2 g−1, 0.36 cm3 g−1). Furthermore, Mg–Ni–La2O3 exhibited outstanding catalytic performance in terms of activity and chemical stability compared to its counterparts. For instance, at a gas hourly space velocity (GHSV) of 30 000 mL g−1 h−1, it afforded 83.2% methane conversion and 90.8% CO2 conversion at 700 °C with no detectable carbon deposition over an operating period of 100 h. The superb DRM catalytic performance of Mg–Ni–La2O3 was attributed to the high specific surface area/porosity, strong metal-support interaction (MSI), and enhanced basicity, in particular the strong basic sites compared to other promoted catalysts. These factors remarkably enhance the catalytic performance and foster resistance to coke deposition. This publication was supported by Qatar University, internal grant number QUCG-CENG-19/20-7. The ?ndings achieved herein are solely the responsibility of the authors. The authors also acknowledge the technical support of Central Laboratories Unit (CLU), Center for Advanced Materials (CAM), and Gas Processing Center (GPC), Qatar University, Doha, Qatar. Scopus

The Raman spectra of borosilicate glass containing 35, 40, and 45 mol % of alkali-earth metal oxide (SrO and BaO) are studied. The structural changes taking place at a gradual substitution of boron oxide by silica are determined. At a high boron oxide content, transformations among borate structural units are predominant because the main part of the modifying oxide reacts with the borate network. When boron is replaced by silicon, the appearance of borosilicate ring structures is observed in alkali-earth borosilicate glass. At the ratio of SiO2/B2O3 > 0.5, a part of the triborate groups and borate structural units containing nonbridging oxygen atoms decreases gradually. When SiO2/B2O3 > 1, the character of the transformations among the Q n structural units changes.

The study of the intermolecular interactions is important to explain the phenomenon occurred on the human body. One of the most important processes that can be studied is the interaction of the peptide with metal ions. In this study, a computational approach was harnessed to predict the interaction and the changes in peptide’s conformation between Cys-Ala peptide which is one of the important amino acids in e-cadherin with some of alkaline earth metal ions. Cys-Ala peptide (Ac-CA-NH2) was used as a molecular model in this calculation. All the molecular structure involved in the interaction was optimized by density functional theory DFT/M06-2X, and basis set 6-31G** to obtain minimum energy, the interaction energies, and the changes in its conformation. The results showed that the interaction energy of Ac-CA-NH2 with alkaline earth metal ions from top to bottom based on the Periodic table is getting higher in a row. The interaction energies of Ac-CA-NH2 with Be2+, Mg2+ and Ca2+ ions are -2.393kcal, -17.489 kcal, and -25.938 kcal respectively. These energies were obtained from the interaction of the peptide with ions in a water solvent. The changes in the peptide's bond length and dihedral angle indicate a conformational change in the Cys-Ala peptide, but it still maintains the trans conformation in its peptide bonds. The results and evaluations of this study may be used for further research considerations and may be applied to enzymes or other peptides that have the Cys-Ala residue.

Anionic oxygen redox chemistry in Li-excess transition metal oxides has emerged as a new paradigm to increase the energy density of rechargeable batteries. However, the anionic redox of oxygen mostly forms the O–O bond, leading to partly irreversible discharge. To address this issue, we demonstrate a new strategy to achieve dual functions of activating cation activity and enhancing oxygen anion redox activity in Li2MnO3 through a light metal (Mg, Ca and Al) substitution of Li. Our first-principle thermodynamic calculations show that Mg2+ substitution in Li2MnO3 prefers locating at the Li+ site, which induces the formation of reductive Mn-ions with electrochemical activity. The substituted local structure of (Li–O–Mg)/2(Li–O–Mn) becomes more electrochemically stable than the specific Li–O–Li local structure in Li2MnO3, which effectively retards O–O combination. Therefore, the reversible capacity (245 mA h g−1) of the optimal substituent compound Li1.5Mg0.5MnO3 is significantly improved compared with that (115 mA h g−1) of Li2MnO3. More importantly, this substitution strategy can be effectively extended to other Li-rich electrodes such as Li3VO4 and Li3NbO4 with Mg-substitution activating cationic redox. The study opens a new avenue in improving the reversible capacity of Li-rich cathode materials through low-cost element substitution.

Bi-Doped nitridated germanate glasses covering the whole NIR region from 800–1600 nm have attracted considerable attention due to their potential application in tunable fiber lasers and optical amplifiers. However, it remains challenging to regulate the luminescence behaviour of Bi because of the coexistence of multi-centers in the glasses. Here, we successfully regulated multi Bi NIR centers to obtain a flatter and ultra-broadband emission in nitridated germanate glasses. By varying the alkaline earth metal fluorides from MgF2 to BaF2, the glass structures were gradually depolymerized. A looser glass network, on one hand, promoted Bi in lower valences to be oxidized into Bi2+ and Bi3+, thus reducing the NIR emission intensity at ∼1150 and ∼1260 nm; on the other hand, it also enhanced the energy transfer from Bi+ to Bi0, which resulted in a relatively flatter emission band. In addition, the depolymerised glass structure could facilitate more nitride bonds, which are favorable for dispersing and stabilizing the new Bi NIR active centers related to germanate for ∼930 and ∼1490 nm emission. This investigation offers an efficient way to manipulate the multi-center luminescence behaviour of Bi in nitridated germanate glasses, and is beneficial to understand the mechanism of Bi NIR emission centers in glasses.

Laser ignition of explosives is believed to be a safe and reliable initiation method to trigger the reaction of energetic materials. Energetic complexes including most primary explosives are a class of important explosives. The determinant of the laser initiation threshold of energetic complexes is still unclear. The coordination metal ions have a significant influence on the properties of energetic complexes. However, the effect of metal ions on the laser ignition ability has not attracted enough attention. To inspect the influence of alkali and alkaline earth metal ions on the laser initiation ability of energetic complexes, sodium(I) (1), potassium(I) (2), magnesium(II) (3), calcium(II) (4), and barium(II) (5) containing energetic complexes based on the ligand 4,4′,5,5′-tetranitro-2,2′-biimidazole (TNBI) were prepared. The crystal structures and thermal behaviors of four new complexes (1, 3, 4, and 5) were characterized. Laser initiation tests were carried out using different laser energy densities. TNBI and all complexes could be initiated and they all exhibited deflagration processes. It is found that the initiation delay times have a definite relationship with the metal ion type. Two alkali metal-containing complexes were easy to initiate, followed by the ligand TNBI, whereas the alkaline earth metal-containing complexes showed longer initiation delay times.

A series of neutral magnesium and calcium complexes bearing an extremely bulky diamido ligand have been synthesised and crystallographically characterised. A number of these complexes feature rare group 2 metal⋯aromatic interactions, such as the η6-coordination of benzene and ‘agostic-like’ C–H coordination, the latter previously unseen in neutral Mg and Ca complexes.