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This study investigated the effect of alkaline-earth metals (X = Be, Mg, Ca) substitution of BFe 2 XH perovskite materials and the potential applications for hydrogen storage utilizing density functional theory (DFT) approach at the GGA-PBE and the HSE06 methods. The mechanical properties of the studied systems demonstrate the mechanical stability of BFe 2 MgH, making it the most mechanically robust compound. While the Pugh ratio suggests that BFe 2 BeH was brittle, while BFe 2 CaH showed greater ductility, anisotropic factors confirm that all compounds are anisotropic, indicating directional dependence in their properties. The electronic band structure analysis using the HSE06 and the GGA-PBE suggests that the studied perovskites are metallic due to a calculated bandgap of zero. In terms of optical/optoelectronic properties, BFe 2 MgH exhibits the highest optical conductivity, absorption coefficient, and energy loss function, indicating its superior ability to absorb light and transfer electrons. For practical applications, the hydrogen storage capacity is assessed, with BFe 2 BeH showing the highest gravimetric and volumetric capacities. These promising results suggest the potential use of BFe 2 BeH as an efficient material for hydrogen storage. • This study investigated the effect of alkaline-earth metals (X = Be, Mg, Ca) substitution of BFe 2 XH perovskite materials. • The study utilized density functional theory (DFT) approach at the GGA-PBE and the HSE06 methods. • The mechanical properties of the studied systems demonstrate the mechanical stability of BFe 2 MgH. • The electronic band structure analysis was performed using HSE06 and the GGA-PBE. • BFe 2 MgH exhibits the highest optical conductivity, absorption coefficient, and energy loss function. [ABSTRACT FROM AUTHOR]

Birch reduction and similar dissolved metal‐type transformations hold significant importance in the organic synthesis toolbox. Historically, the field has been dominated by alkali metal reductants. In this study, we report that largely neglected, low‐reactive alkaline earth metals can become powerful and affordable reductants when used in a ball mill under essentially solvent‐free conditions, in the presence of ethylenediamine and THF as liquid additives. Calcium can reduce both electron‐deficient and electron‐rich arenes, with yields of products similar to those obtained with lithium metal. Magnesium reveals enhanced reducing power, enabling the reduction of benzoic acids while keeping electron‐rich aromatic moieties intact and allows for chemoselective transformations. The developed mechanochemical approach uses readily available and safer‐to‐handle metals, operates under air and ambient temperature conditions, and can be used for gram‐scale preparations. Finally, we demonstrate that the developed conditions can be used for other dissolved metal‐type reductive transformations, including reductive amination, deoxygenation, dehalogenation, alkene and alkyne reductions. [ABSTRACT FROM AUTHOR]

This study investigated the differences and correlation between the occurrence characteristics of alkali and alkaline earth metals (AAEMs) among different maceral groups in high-alkali, high-inertinite coal, and provides scientific guidance for the co-separation of AAEMs and inertinite groups in Xinjiang coal. The total AAEMs of inertinite-enriched samples were significantly higher than those in raw coals and vitrinite-enriched samples. Five-step sequential extraction showed that Na mainly occurs as water-soluble sodium (Na-Water) in raw coal and inertinite-enriched samples, accounting for about 53% of the total content, while it exists as organic sodium (Na-NH4Cl and Na-EDTA) in vitrinite-enriched samples, accounting for about 52% of the total content. Ca and Mg are both mainly present in organic form (Ca/Mg-NH4Cl and Ca/Mg-EDTA) in all the samples, with slightly higher proportions present in vitrinite-enriched samples. The contents of K are low in all the samples, which exist in an insoluble state (K-I). Combined microscopy and SEM-EDS analyses have revealed that the localized enrichment of Na in raw coal and inertinite-enriched samples occurs in the inertinite cell cavity, which primarily exists as NaHCO3 combined with quartz crystals, with a maximum content of up to 5.85 wt%. In this study, although EDS spectra could not directly characterize organic Ca and Mg, dolomite and calcite minerals were repeatedly found in the inertinite cell cavity. Moreover, the contents of Ca and Mg in the vitrinite-enriched samples were significantly lower than those in the other samples, which suggests that Ca and Mg are enriched with the inertinite groups. The localized enrichment of AAEMs could not be detected in any of the vitrinite-enriched samples. In summary, though there are significant differences between the occurrence modes of AAEMs in different maceral groups of high-alkali coal, AAEMs have a strong affinity with inertinite, which may be due to the inertinite's abundant pore structures. [ABSTRACT FROM AUTHOR]

The low-carbon, clean, and efficient utilization of the Zhundong coal is greatly limited by some severe problems such as ash accumulation, slagging, and CO2 emissions in the conventional combustion and utilization processes. The adoption of low-rank coal pyrolysis at low and moderate temperatures to produce semicoke, tar, and pyrolysis gas is a leading technology for the utilization of classified coal. Based on the characteristic of high alkali gasification activity of pyrolysis semicoke, the chemical-looping combustion technology is adopted to achieve a low-carbon, clean, and efficient conversion of the Zhundong coal semicoke. The in-situ gasification chemical-looping combustion characteristics of the Zhundong coal semicoke are studied in a fixed bed, in which CO2 is selected as the gasification agent and hematite is considered as the oxygen carrier. The study of migration and transformation laws of alkali and alkaline earth metals (AAEMs) in the Zhundong coal semicoke also is performed. The experimental result indicates that the addition of the hematite oxygen carrier can significantly improve the CO2 concentration of the flue gas at the outlet of the fixed bed reactor. However, CO2 concentration increases first and then remains constant with the increase in the mass ratio of the oxygen carrier and semicoke (mOC/mC). The optimal mOC/mC is determined as 50∶1. In this case, the CO2 selectivity of the flue gas at the outlet of the fixed-bed reactor is decreased by 8.95 percentage points at the pyrolysis temperature of 700 ℃ after acid washing and deashing treatment, indicating that the chemical-looping combustion performance of the Zhundong coal semicoke can be significantly affected by the catalytic activity of AAEMs in the semicoke. The distribution of AAEMs on the surface of the Zhundong coal semicoke is affected by the hematite oxygen carrier. Compared with the absence of the hematite oxygen carrier, more obvious cluster enrichment on the surface of semicoke for Na and K elements is found. An obvious dependency relationship for the distribution of Ca and Mg elements is observed. When the in-situ gasification chemical-looping combustion is adopted, the active AAEMs elements in the semicoke are migrated and transformed into hematite. High melting point minerals such as nepheline (NaAlSiO4), potassium feldspar (KAlSi3O8), gehlenite (Ca2Al2SiO7), and magnesium olivine (Mg2SiO4) are generated, effectively suppressing the volatilization of AAEMs in the Zhundong coal semicoke.

The effects of single‐vacancy and double‐vacancy doping with alkaline‐earth metals on the stability, electronic structure, charge transfer, and optical properties of molybdenum ditelluride in the monolayer defective state (MoTe2) have been investigated using first‐principles methods. It is found that the structure of the molybdenum ditelluride system is more stable after double Te vacancies, with direct band‐gap to indirect band‐gap transitions occurring in single Te vacancies and Mo vacancies, and semiconductor to quasi‐metal transitions occurring in double Mo vacancies. The binding energy in the defect state system of molybdenum ditelluride after vacancy defects is always negative, and the structure remains stable. In this paper, the most stable double Te vacancy state was selected for substitutional doping with alkaline‐earth metals, and the Be atoms were doped with the largest amount of morphology, and Ca atoms were doped with the most pronounced decrease in band gap value. The direct band‐gap semiconductor is maintained after doping with Be atoms. Doping with Mg, Sr and Ba changes the band‐gap from direct to indirect. The double Te defect state MoTe2 doped with Ca atoms has a tendency to transition to a quasi‐metal. Regarding photoelectric properties, the system is blue‐shifted on both the absorption and reflection peaks. [ABSTRACT FROM AUTHOR]

Hybrid metal halides are an extraordinary class of optoelectronic materials with extensive applications. To further diversify and study the in‐depth structure‐property relations, we report here a new family of 21 zero‐dimensional hybrid bimetallic chlorides with the general formula A(L)n[BClm] (A=rare earth (RE), alkaline earth metals and Mn; L=solvent ligand; and B=Sb, Bi and Te). The RE(DMSO)8[BCl6] (RE=La, Ce, Sm, Eu, Tb, and Dy; DMSO=dimethyl sulfoxide) series shows broadband emission attributed to triplet radiative recombination from Sb and Bi, incorporating the characteristic emission of RE metals, where Eu(DMSO)8[BiCl6] shows a staggering PL quantum yield of 94 %. The pseudo‐octahedral [SbCl5] with Cl vacancy in AII(DMSO)6[SbCl5] (AII=Mg, Ca and Mn) and the square pyramidal [SbCl5] in AII(TMSO)6[SbCl5] (TMSO=tetramethylene sulfoxide) enhance the stereoactive expression of the 5 s2 lone pairs of Sb3+, giving rise to the observation of dual‐band emission of singlet and triplet emission, respectively. A series of Te(IV) analogues have been characterized, showing blue‐light‐excitable single‐band emission. This work expands the materials space for hybrid bimetallic halides with an emphasis on harnessing the RE elements, and provides important insights into designing new emitters and regulating their properties. [ABSTRACT FROM AUTHOR]

In the pursuit of reliable energy storage solutions, the significance of engineering electrodes cannot be overstated. Previous research has explored the use of surface modifiers (SMs), such as single-side fluorinated graphene, to enhance the thermodynamic stability of ion intercalation when applied atop few-layer graphene (FLG). As we seek alternatives to lithium-ion batteries (LIBs), earth-abundant elements like sodium and potassium have emerged as promising candidates. However, a comprehensive investigation into staging intercalation has been lacking thus far. By delving into staging assemblies, we have uncovered a previously unknown intercalation site that offers the most energetically favorable binding. Here, we study the first three elements in both alkali (Li, Na, K) and alkaline (Be, Mg, Ca) earth metals. Furthermore, the precise mechanism underlying this intercalation system has remained elusive in prior studies. In our work, we employed density functional theory calculations with advanced hybrid functionals to determine the electrical properties at various stages of intercalation. This approach has been proven to yield more accurate and reliable electrical information. Through the analysis of projecting density of states and Mulliken population, we have gained valuable insights into the intricate interactions among the SM, ions, and FLG as the ions progressively insert into the structures. Notably, we expanded our investigation beyond lithium and explored the effectiveness of the SM on ions with varying radii and valence, encompassing six alkali and alkaline earth metals. Additionally, we discovered that the number of graphene layers significantly influences the binding energy. Our findings present groundbreaking concepts for material design, offering diverse and economically viable alternatives to LIBs. Furthermore, they serve as a valuable reference for fine-tuning electrical properties through staging intercalation and the application of SMs. [ABSTRACT FROM AUTHOR]

This study investigated the differences and correlation between the occurrence characteristics of alkali and alkaline earth metals (AAEMs) among different maceral groups in high-alkali, high-inertinite coal, and provides scientific guidance for the co-separation of AAEMs and inertinite groups in Xinjiang coal. The total AAEMs of inertinite-enriched samples were significantly higher than those in raw coals and vitrinite-enriched samples. Five-step sequential extraction showed that Na mainly occurs as water-soluble sodium (Na-Water) in raw coal and inertinite-enriched samples, accounting for about 53% of the total content, while it exists as organic sodium (Na-NH4Cl and Na-EDTA) in vitrinite-enriched samples, accounting for about 52% of the total content. Ca and Mg are both mainly present in organic form (Ca/Mg-NH4Cl and Ca/Mg-EDTA) in all the samples, with slightly higher proportions present in vitrinite-enriched samples. The contents of K are low in all the samples, which exist in an insoluble state (K-I). Combined microscopy and SEM-EDS analyses have revealed that the localized enrichment of Na in raw coal and inertinite-enriched samples occurs in the inertinite cell cavity, which primarily exists as NaHCO3 combined with quartz crystals, with a maximum content of up to 5.85 wt%. In this study, although EDS spectra could not directly characterize organic Ca and Mg, dolomite and calcite minerals were repeatedly found in the inertinite cell cavity. Moreover, the contents of Ca and Mg in the vitrinite-enriched samples were significantly lower than those in the other samples, which suggests that Ca and Mg are enriched with the inertinite groups. The localized enrichment of AAEMs could not be detected in any of the vitrinite-enriched samples. In summary, though there are significant differences between the occurrence modes of AAEMs in different maceral groups of high-alkali coal, AAEMs have a strong affinity with inertinite, which may be due to the inertinite’s abundant pore structures.

A significant problem in the area of rechargeable alkali ion battery technologies is the exploration of anode materials with overall high specific capacities and superior physical properties. By using first-principles calculations, we have determined that monolayer TiSi2N4 is precisely such a potential anode candidate. Its demonstrated dynamic, thermal, mechanical, and energetic stabilities make it feasible for experimental realization. An important benefit of the electrode conductivity is that the electronic structure reveals that the pristine system experiences a change from a semiconductor to a metal throughout the entire alkali adsorption process. What's more interesting is that monolayer TiSi2N4 can support up to double-sided 3-layer ad-atoms, resulting in extremely high theoretical capacities for Li, Na, Mg, and K of 1004, 854, 492 and 531 mA h g−1 and low average open-circuit voltages of 0.55, 0.25, 0.55, and −1.3 V, respectively. Alkali diffusion on the surface has been demonstrated to occur extremely quickly, with migration energy barriers for Li, Na, Mg, and K as low as 0.25, 0.14, 0.10, and 0.07 eV, respectively. The results reveal that the migration barrier energy is the lowest for Li and Mg from path-2 and Na and K from path-1. Overall, these findings suggest that monolayer TiSi2N4 is a suitable anode candidate for use in high-performance and low-cost metal-ion batteries. [ABSTRACT FROM AUTHOR]

The study of alkaline earth metal complexes is undergoing a renaissance. Stable molecular species featuring Mg–Mg bonds were reported in 2007 and their reactivity has since been intensively investigated. Motivated by this work, efforts have also been devoted to the synthesis of complexes featuring Be–Be and Ca–Ca bonds. These collective endeavours have revealed that the chemistry of the group 2 metals is richer and more complex than had previously been appreciated. Here, a discussion of the nature of homometallic alkaline earth bonding is presented, recent synthetic advances are described, and future directions are considered. [ABSTRACT FROM AUTHOR]

A survey of the trends in metal–ligand coordination and hydrogen bonding has been carried out on complexes of singly deprotonated cyanuric acid CY− and alkaline earth metals, synthesised from aqueous solution and characterised by X-ray crystallography. The involvement of cyanurate in metal coordination increases from Mg through Ca and Sr to Ba relative to coordination by water, in parallel with increasing ionic radius and coordination number. The incidence of the bridging of metal centres by both water and cyanurate also increases in this series. The Mg complex [Mg(H2O)6][CY]2·2H2O contains hexaaqua-coordinated cations, uncoordinated CY− anions, and additional water molecules. The Ca and Sr complexes {[Ca(CY)(H2O)3][CY]}∞ and {[Sr(CY)2(H2O)4]}∞ feature polymeric chains of coordinated metal ions, the Ca complex with uncoordinated anions and the Sr complex with all potential ligands coordinated. The Ba complex {[Ba(CY)2(H2O)2]}∞ has a two-dimensional coordination network. Extensive hydrogen bonding plays a key role in generating a three-dimensional network in all four structures. The competition between cyanurate and water for coordination to the alkaline earth metal cations, and that between coordination and the hydrogen bonding propensities of the cyanurate anion, appear to be finely balanced, with the structural outcomes depending on the relative sizes and degrees of hardness of the four cations of the group.

Superconductivity in two-dimensional materials has attracted considerable attention. A new material belonging to the family of Janus transition metal dichalcogenides with out-of-plane structural asymmetry has been recently found to show interesting physical and chemical properties. Using density functional theory and density functional perturbation theory, within the generalized gradient approximation with van der Waals correction, we performed a detailed investigation of the electronic structure, phonon dispersion, Eliashberg spectral function, and electron-phonon coupling of Janus MSSe bilayers (M = Mo or W) and the Janus MoSSe/WSSe heterostructure intercalated with alkali metals (Li, Na, and K) or alkaline earth metals (Mg, Ca, and Sr). We found that the Janus MoSSe bilayer, Janus WSSe bilayer, and Janus MoSSe/WSSe heterostructure transform from a direct band gap semiconductor to a metal or semimetal due to charge transfer from intercalated atoms to the Se and S planes. We showed that all compounds are dynamically stable conventional superconductors. In addition, the Janus heterostructure MoSSe/WSSe intercalated with K exhibits the highest electron-phonon coupling of about 2.12 and the highest superconducting transition temperature of about 14.77 K. Our results indicate the potential application of the Janus materials we investigated in superconductivity.

The multiferroic Y-type hexaferrites BaxSr2−xMe2Fe12−yAlyO22 (Me = Zn2+, Co2+, Mg2+, etc.) have attracted much attention due to their giant magnetoelectric (ME) effect up to room temperature and low modulated magnetic field by the chemical doping control of the complex magnetic phases. However, the research of substitution between the Me ions is rare. As doping at the Me ion site can combine the advantages of both, e.g., higher magnetic ordering temperature in Co2 and stronger ME coefficient in Mg2 Y-type hexaferrites, herein, we report the stability and switching of magnetoelectric states in the Y-type hexaferrites Ba0.5Sr1.5CoMgFe11AlO22 single crystals. Our results demonstrate that substituting half of the Mg2+ with Co2+ enhances the transition temperature of the alternating longitudinal conical phase to proper screw spin order up to room temperature compared to those Mg2 Y-type hexaferrites. Simultaneous occurrence of in-plane and out-of-plane ferroelectric polarization is observed, alongside comparable spontaneous magnetization. It was found that the in-plane spin-driven polarization can be reversible below 50 K with a substantial ME coefficient α = −8000 ps/m but becomes irreversible at 100 K. This reversal in the sign of the ME coefficient signifies the transition between two distinct ME states at high temperature. The reversibility and irreversibility of spin-induced polarization are discussed within the framework of free energy based on the ferroelectric phase, which prevail in numerous Y-type hexaferrites. Our results provide insights into understanding the role of the Me ions in the magnetoelectric coupling in Y-type hexaferrites. [ABSTRACT FROM AUTHOR]

We performed high-level ab initio quantum chemical calculations, incorporating higher-order excitations, spin–orbit coupling (SOC), and the Gaunt interaction, to calculate the electron affinities (EAs) of alkaline earth (AE) metal atoms (Ca, Sr, Ba, and Ra), which are notably small. The coupled-cluster singles and doubles with perturbative triples [CCSD(T)] method is insufficient to accurately calculate the EAs of AE metal atoms. Higher-order excitations proved crucial, with the coupled-cluster singles, doubles, and triples with perturbative quadruples [CCSDT(2)Q] method effectively capturing dynamic electron correlation effects. The contributions of SOC (ΔESOs) to the EAs calculated using the multireference configuration interaction method with the Davidson correction, including SOC, positively enhance the EAs; however, these contributions are overestimated. The Dirac–Hartree–Fock (DHF)-CCSD(T) method addresses this overestimation and provides reasonable values for ΔESO (ΔESO−D). Employing additional sets of diffuse and core–valence correlation basis sets is critical for accurately calculating the EAs of AE metal atoms. The contributions of the Gaunt interaction (ΔEGaunt) to the EAs of AE metal atoms are negligible. Notably, the CCSDT(2)Q with the complete basis set limit + ΔESO−D + ΔEGaunt produced EA values for Ca, Sr, and Ba that closely aligned with experimental data and achieved accuracy exceeding the chemical accuracy. Based on our findings, the accurately proposed EA for Ra is 9.88 kJ/mol. [ABSTRACT FROM AUTHOR]

Hydrated cation–π interactions at liquid–solid interfaces between hydrated cations and aromatic ring structures of carbon-based materials are pivotal in many material, biological, and chemical processes, and water serves as a crucial mediator in these interactions. However, a full understanding of the hydrated cation–π interactions between hydrated alkaline earth cations and aromatic ring structures, such as graphene remains elusive. Here, we present a molecular picture of hydrated cation–π interactions for Mg2+ and Ca2+ by using the density functional theory methods. Theoretical results show that the graphene sheet can distort the hydration shell of the hydrated Ca2+ to interact with Ca2+ directly, which is water–cation–π interactions. In contrast, the hydration shell of the hydrated Mg2+ is quite stable and the graphene sheet interacts with Mg2+ indirectly, mediated by water molecules, which is the cation–water–π interactions. These results lead to the anomalous order of adsorption energies for these alkaline earth cations, with hydrated Mg2+–π < hydrated Ca2+–π when the number of water molecules is large (n ≥ 6), contrary to the order observed for cation–π interactions in the absence of water molecules (n = 0). The behavior of hydrated alkaline earth cations adsorbed on a graphene surface is mainly attributed to the competition between the cation–π interactions and hydration effects. These findings provide valuable details of the structures and the adsorption energy of hydrated alkaline earth cations adsorbed onto the graphene surface. [ABSTRACT FROM AUTHOR]

The chemical flexibility of metal-organic frameworks (MOFs) offers an ideal platform to tune structure and composition for specific applications, from gas sensing to catalysis and from photoelectric conversion to energy storage. This variability gives rise to a large configurational space that can be efficiently explored using high-throughput computational methods. In this work, we investigate from first principles the structural and electronic properties of MOF-5 variants obtained by replacing Zn with Be, Mg, Cd, Ca, Sr, and Ba and by functionalizing the originally H-passivated linkers with CH3, NO2, Cl, Br, NH2, OH, and COOH groups. To build and analyze the resulting 56 structures, we employ density-functional theory calculations embedded in an in-house developed library for automatized calculations. Our findings reveal that structural properties are mainly defined by metal atoms and large functional groups, which distort the lattice and modify coordination. The formation energy is largely influenced by functionalization and enhanced by COOH and OH groups, which promote the formation of hydrogen bonds. The charge distribution within the linker is especially influenced by functional groups with electron-withdrawing properties, while the metal nodes play a minor role. Likewise, the bandgap size is crucially determined by ligand functionalization. The smallest gaps are found with NH2 and OH groups, which introduce localized orbitals at the top of the valence band. This characteristic makes these functionalizations particularly promising for the design of MOF-5 variants with enhanced gas uptake and sensing properties. [ABSTRACT FROM AUTHOR]

Controlling and understanding charge state and metal coordination in carbon nanomaterials is crucial to harnessing their unique properties. Here we describe the synthesis of the well‐defined fulleride complex [{(Mesnacnac)Mg}6C70], 2, (Mesnacnac)=HC(MeCNMes)2, Mes=2,4,6‐Me3C6H2, from the reaction of the β‐diketiminate magnesium(I) complex [{(Mesnacnac)Mg}2] with C70 in aromatic solvents. The molecular structure of complex 2 was determined, providing the first high‐quality structural study of a complex with the C706− ion. In combination with solution state NMR spectroscopic and DFT computational studies, the changes in geometry and charge distribution in the various atom and bond types of the fulleride unit were investigated. Additionally, the influence of the (Mesnacnac)Mg+ cations on the global and local fulleride coordination environment was examined. [ABSTRACT FROM AUTHOR]

The quest for planar hypercoordinate atoms (phA) beyond six has predominantly focused on transition metals, with dodecacoordination being the highest reported thus far. Extending this bonding scenario to main-group elements, which typically lack d orbitals despite their larger atomic radius, has posed significant challenges. Intrigued by the potentiality of covalent bonding formation using the d orbitals of the heavier alkaline-earth metals (Ae = Ca, Sr, Ba), the so-called "honorary transition metals", we aim to push the boundaries of planar hypercoordination. By including rings formed by 12-15 atoms of boron-carbon and Ae centers, we propose a design scheme of 180 candidates with a phA. Further systematic screening, structural examination, and stability assessments identified 10 potential clusters with a planar hypercoordinate alkaline-earth metal (phAe) as the lowest-energy form. These unconventional structures embody planar dodeca-, trideca-, tetradeca-, and pentadecacoordinate atoms. Chemical bonding analyses reveal the important role of Ae d orbitals in facilitating covalent interactions between the central Ae atom and the surrounding boron-carbon rings, thereby establishing a new record for coordination numbers in the two-dimensional realm.

Alkaline earth (AE) metal complexes have garnered significant interest in various functional fields due to their nontoxicity, low density, and low cost. However, there is a lack of systematic investigation into the structural characteristics and physical properties of AE‐metal‐organic frameworks (MOFs). In this research, we synthesized isostructural MOFs consisting of AE4(μ4‐Cl) clusters bridged by benzo‐(1,2;3,4;5,6)‐tris(thiophene‐2′‐carboxylic acid) (BTTC3−) ligands. The resulting structure forms a truncated octahedral cage denoted as [AE4(m4‐Cl)]6(BTTC)8, which further linked to a porous three‐dimensional framework. Among the investigated AE ions (Ca, Sr, and Ba), the Ca4‐MOF demonstrated good chemical stability in water compared to Sr4‐MOF and Ba4‐MOF. The N2 adsorption and solid‐state UV‐vis‐NIR absorption behaviors were evaluated for all AE4‐MOFs, showing similar trends among the different metal ions. Additionally, the proton conduction study revealed that the Ca4‐MOF exhibited ultra‐high proton conductivity, reaching 3.52×10−2 S cm−1 at 343 K and 98 % RH. Notably, the introduction of LiCl via guest exchange resulted in an improved proton conduction of up to 6.36×10−2 S cm−1 under similar conditions in the modified LiCl@Ca4‐MOF. The findings shed light on the regulation of physical properties and proton conductivity of AE‐MOFs, providing valuable insights for their potential applications in various fields. [ABSTRACT FROM AUTHOR]

A significant problem in the area of rechargeable alkali ion battery technologies is the exploration of anode materials with overall high specific capacities and superior physical properties. By using first-principles calculations, we have determined that monolayer TiSi 2 N 4 is precisely such a potential anode candidate. Its demonstrated dynamic, thermal, mechanical, and energetic stabilities make it feasible for experimental realization. An important benefit of the electrode conductivity is that the electronic structure reveals that the pristine system experiences a change from a semiconductor to a metal throughout the entire alkali adsorption process. What's more interesting is that monolayer TiSi 2 N 4 can support up to double-sided 3-layer ad-atoms, resulting in extremely high theoretical capacities for Li, Na, Mg, and K of 1004, 854, 492 and 531 mA h g -1 and low average open-circuit voltages of 0.55, 0.25, 0.55, and -1.3 V, respectively. Alkali diffusion on the surface has been demonstrated to occur extremely quickly, with migration energy barriers for Li, Na, Mg, and K as low as 0.25, 0.14, 0.10, and 0.07 eV, respectively. The results reveal that the migration barrier energy is the lowest for Li and Mg from path-2 and Na and K from path-1. Overall, these findings suggest that monolayer TiSi 2 N 4 is a suitable anode candidate for use in high-performance and low-cost metal-ion batteries.

The potential of B20 cluster decorated with alkali metals (AM = Li, Na, and K) and alkaline earth metals (AEM = Ca, Mg, and Be) to adsorb hydrogen molecules is investigated using density functional theory (DFT). The Bader's topological parameters suggest the presence of non-bonded interaction between the bare structures and H2 molecules. Global reactivity descriptor values confirm that the structures remain stable even after the adsorption of H2 molecules. The results indicate that Na adorned B20 (B20Na2) can store up to 12H2 molecules, with a hydrogen storage capacity of 8.33 wt% and an average adsorption energy is 0.127 eV/H2. The findings suggest that B20 cluster decorated with AM and AEM have the ability to be a promising hydrogen storage material. Additionally, to gain insights into the adsorption and desorption behaviors of H2 molecules, ADMP molecular dynamics simulations methods were performed at room temperatures. [ABSTRACT FROM AUTHOR]

Harmonic and anharmonic normal modes were computed for the alkaline earth metal carbonyl complexes, namely Ba(CO)+, Ba(CO)-, Ba(CO)2, Ca(CO)2, Ba(CO)3, and Ba(CO)4, using various DFT functionals and methods in combination with three different basis sets (cc-pVTZ-DK3, cc-pVTZ-DK2 cc-pVTZ-X2C, and def2-TZVPP for Ba and Ca atoms). Divergent results were observed among these systems for the carbonyl stretching mode. This study underscores the inadequacy of the current computational methods, ongoing need for a comprehensive understanding of these newly synthesized carbonyl complexes and the development of a benchmark method that can effectively address the vibrational frequencies of all these systems. [ABSTRACT FROM AUTHOR]

In this paper, poplar sawdust (PS), walnut shell (WS), sugarcane bagasse (SB), polyethylene (PE), and paper napkin (PN) were selected as typical organic solid waste for the study of steam (co-)gasification coupled with on-line analysis of H 2 -rich syngas. The carbon conversion efficiency of PE is only 10.8% and needs to be improved. The mixture of SB + PE exhibited the most pronounced positive synergies, with H 2 /CO reaching 2.40 without catalyst and the synergistic indices of 0.320, 0.298, and 0.226 for H 2 yield, syngas yield, and H 2 /CO, respectively, and these synergies were evident throughout the entire gasification process. The synergistic mechanism was analyzed through the interphase migration of alkali and alkaline earth metals and the morphological properties of the char. Compared with the co-gasification at 900 °C, the synergistic indices of the SB + PE co-gasification parameters at 800 °C were reduced to different degrees, and even the co-gasification at 700 °C showed a remarkable negative synergism. [Display omitted] • Steam co-gasification of various MSWs was carried out online for H 2 -rich syngas. • Co-gasification of SB + PE showed optimal synergy for both H 2 yield and H 2 /CO. • Synergistic mechanism was discussed in terms of AAEMs migration and char structure. • High temperatures of 800∼900 °C contributed to unleashing synergistic potentials. [ABSTRACT FROM AUTHOR]

The transition metal properties of heavy alkaline earth metals have been extensively studied, and their neighbouring heavy alkali metals have been limited to the interactions with CO‐σ ligands. Based on this, the complexes [K2M(COT)2]− (M=K, Rb, Cs) interacting with heavy alkali metals and COT‐π ligands are theoretically designed in this paper. The electronic structure analysis showed that the three complexes had 10 occupied molecular orbitals (MOs), in which 8 of them were related to the atomic orbitals (AOs) of central alkali metals, including 4 d orbitals (dxy, dx2−y2, dxz, dyz), so they also exhibited the typical behaviors of transition metals. NBO analysis indicated that the central metals in these complexes are common valence of +1, the ligands are negative, so the electrostatic coulomb interaction between positive and negative ions makes them more stable. This can be reflected by the high binding energies of −585.8 to −594.0 kcal/mol, which are much higher than those of −6.5 to −63.3 kcal/mol for the trace amount of complexes combined by neutral metals and ligands. It would be a feasible strategy for the design of the macrosynthesis of related complexes by combining the positive ions and negative ligands, which can stabilize the complexes through the favorable Coulomb attractions. [ABSTRACT FROM AUTHOR]

In this paper, the removal behavior of alkali and alkaline earth metals (AAEMs) and the evolution of microscopic characteristics in high alkali coal under the leaching of inorganic and organic acids are studied. The results show inorganic acids have better effect on the removal of AAEMs because of their stronger ability to convert carboxylate and phenol salts into covalent carboxylic acids and phenols. Citric acid has a slightly weaker effect than inorganic acids, and oxalic acid has the least effect. The improvement of slagging characteristics is consistent with the removal ability. Sulfuric acid, hydrochloric acid and citric acid are more effective in enhancing the calorific value of coal, with an enhancement of about 0.60 MJ/kg. After leaching, the pores and cracks in the coal are developed, and the mesopores have a tendency to shift to a lower pore size range. This trend is most pronounced in citric acid leached coal and hydrochloric acid leached coal. Sulfuric acid seriously damage the surface morphology, which results in a tendency of large pore transfer in S-form coal. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of the interaction of titanium melt with of zirconates BaZrO _3 and SrZrO _3 , as well as titanate SrTiO _3 under vacuum conditions and in an inert atmosphere at normal pressure. An original titanium heating method was used during the experiments. It eliminated the melt circulation at the interface between the solid and liquid phases. The method was based on resistive electrical heating of a Grade 2 titanium alloy rod or strip pressed into BaZrO _3 , SrZrO _3 and SrTiO _3 powders. Studied the structure, elemental, and phase composition of the products formed during various (up to 300 s) contact of titanium melt with surface zirconates and titaniums. The phase composition was compared with the products obtained by heating compacts from a mixture of titanium powders with BaZrO _3 , SrZrO _3 and SrTiO _3 powders. It was shown based on the results obtained that titanium, upon contact with these ceramic materials dissolves zirconium and oxygen and reduces barium and strontium to a metallic state. Barium and strontium evaporated due to the high vapor pressure at the experimental temperature, and caused the melt to splash or form a vapor layer that reduced the interaction rate of the melt with the ceramic. When a titanium melt interacted with BaZrO _3 and SrZrO _3 intermediate phases were not formed in quantities sufficient for their identification. The Sr _3 Zr _2 O _7 phase was formed in small quantities during heating a mixture of Ti+SrZrO _3 powders. When a titanium melt interacted with SrTiO _3 , a layer of an intermediate phase was formed, similar in composition to TiO _2 . Equations for the chemical reaction of the interaction of titanium with the indicated zirconates and titanate were compiled based on the experimental data obtained. It has been shown that titanium melt weted the surface of BaZrO _3 , SrZrO _3 powders well and poorly weted the surface of SrTiO _3 powder.