Stable Oxoborate with Edge-Sharing BO4 Tetrahedra Synthesized under Ambient Pressure

First-principles modeling of H2CO3 molecular adsorption on CaSiO3(001) surface for application in the sequestration and utilization of CO2

This work employed density functional theory (DFT) to further study the adsorption of H2CO3, HCO3-, and CO32- on the CaSiO3(001) surface, which could provide additional insights into the mechanism of carbonation on the CaSiO3 surface. It was concluded that the carbonation of CO2 promoted carbon sequestration, whereby the aqueous carbonation route increased the reaction rate substantially compared to direct gas-solid carbonation. H2CO3 is more conducive to CO2 sequestration, which can be attributed to the interaction of H atoms with the surface. Further, H2CO3 can be converted into HCO3- or CO32- on the CaO-terminated (001) surface, whereas only HCO3- was formed on the SiO-terminated (001) surface. All the adsorption energies of H2CO3 were negative, suggesting that H2CO3 adsorption was energetically stable and spontaneous. The most likely adsorption model of HCO3-, having negative adsorption energy, was the one adsorbed on the SiO-terminated (001) surface, in which HCO3- is transformed into CO32-. The other adsorption models of HCO3- and all the adsorption models of CO32- have positive adsorption energies. Considering the adsorption process of H2CO3, HCO3- and CO32- adsorption reactions may occur successively to some extent depending on the environment.

Finding a Deep-UV Borate BaZnB4 O8 with Edge-sharing [BO4 ] Tetrahedra and Strong Optical Anisotropy

The polarization modulation of deep-UV light is an important process that incorporates functionality to selectively respond to light-mater interaction. Typically, optical anisotropy is foremost to the use efficiency of deep-UV birefringent crystals. Herein, a new congruently melting polyborate with extremely large birefringence (Δn₍₀₀₁₎ =0.14@589.3 nm) and band gap (6.89 eV) is discovered as a high performance birefringent crystal, which breaks the current deadlock of deep-UV polyborates that usually show small birefringence. The rigid tetrahedra, including [ZnO₄ ] and edge-sharing [BO₄ ] tetrahedra, make all the planar [BO₃ ] triangles in the lattice adopt preferential arrangement and thereby lead to an extraordinary large birefringence that is larger than all the deep-UV borates with experimentally measured values. Structural analyses with the additional theoretical calculations were used to study the origin of strong optical anisotropy in BaZnB₄ O₈ .

γ-BaB2O4: High-Pressure High-Temperature Polymorph of Barium Borate with Edge-Sharing BO4 Tetrahedra

The α- and β-modifications of barium metaborate are important functional materials used in optoelectronic devices. A new theoretically predicted modification of BaB₂O₄ has been synthesized under conditions of 3 GPa and 900 °C, using the DIA-type apparatus. The new high-pressure modification, γ-BaB₂O₄, crystallizes in a centrosymmetrical group of monoclinic syngony (P2₁/n (#14), a = 4.6392(4) Å, b = 10.2532(14) Å, c = 7.066(1) Å, β = 91.363(10)°, Z = 4). A distinctive feature of the γ-BaB₂O₄ structure is the presence of edge-sharing tetrahedra [B₂O₆] which form infinite double chains _∞[B₄O₄O_8/2] stretching along the a axis. The number of known structural types with the [B₂O₆] group is limited. Phase γ-BaB₂O₄ has the shortest distance between boron atoms of shared tetrahedra among all currently known compounds. The [B₂O₆] group angles are 95.5° and 105.5°. Thermodynamic stability and electronic properties of the γ-BaB₂O₄ modification were studied. The width of the band gap, calculated using the HSE06 functional, is 7.045 eV which implies transparency in the deep-UV region. Experimental and numerical methods which demonstrate a good match were used to the study the Raman spectra of γ-BaB₂O₄ and β-BaB₂O₄ modifications. In the Raman spectra of γ-BaB₂O₄, the most intense band at a frequency of 853 cm^-1 was found to correspond to the symmetric bending mode of the B-O-B-O ring in edge-sharing tetrahedra.

Recent Advances in Crystalline Oxidopolyborate Complexes of d-Block or p-Block Metals: Structural Aspects, Syntheses, and Physical Properties

Crystalline materials containing hybrid inorganic–organic metal borates (complexes with oxidoborate ligands) display a variety of novel framework building blocks. The structural aspects of these hybrid metallaoxidoborates containing Cd^(II), Co^(II), Cu^(II), Ga^(III), In^(III), Mn^(II), Ni^(II) or Zn^(II) metal centers are discussed in this review. The review describes synthetic approaches to these hybrid materials, their physical properties, their spectroscopic properties and their potential applications.

RbMT3 (BO3 )2 O3 (M=Ba, Sr; T=Al, Ga): New Double-Layered Oxyborates Constructed from [BO3 ] Triangles and [TO4 ] Tetrahedra

Four new alumino-/galloborates RbMT₃ (BO₃ )₂ O₃ (M=Ba, Sr; T=Al, Ga) have been synthesized for the first time by using a high-temperature solution method. All the title compounds have Sr₂ Be₂ B₂ O₇ -like structures, in which the [BO₃ ] triangles and [TO₄ ] tetrahedra form the final double-layered configurations with the M- and Rb-site atoms located between and in the double layer, respectively. The structure evolution from Sr₂ Be₂ B₂ O₇ to RbMT₃ (BO₃ )₂ O₃ series is discussed. The broader energy bandgaps in Al-based borates when compared with Ga-based ones can be entirely attributed to the location of Al/Ga s orbitals near the Fermi surface. Both experimental and computational approaches were used to study their structure-property relationships.

Pb2.28Ba1.72B10O19 featuring a three-dimensional B–O anionic network with edge-sharing [BO4] obtained under ambient pressure

The unique borate Pb_2.28Ba_1.72B₁₀O₁₉ containing a three-dimensional B–O anionic network with edge-sharing [BO₄] was obtained under ambient pressure, featuring an extremely large B–B interatomic distance (d_B–B) and small internal O–B–O angles (∠_{in(O–B–O)}).

High-pressure synthesis of REB5O8(OH)2 (RE = Ho, Er, Tm)

The rare earth oxoborates REB5O8(OH)2 (RE = Ho, Er, Tm) were synthesized in a Walker-type multianvil apparatus at a pressure of 2.5 GPa and a temperature of 673 K. Single-crystal X-ray diffraction data provided the basis for the structure solution and refinement. The compounds crystallize in the monoclinic space group C2 (no. 5) and are composed of a layer-like structure containing dreier and sechser rings of corner sharing [BO4]5− tetrahedra. The rare earth metal cations are coordinated between two adjacent sechser rings. Further characterization was performed utilizing IR spectroscopy.

La3 B6 O13 (OH): The First Acentric High-Pressure Borate Displaying Edge-Sharing BO4 Tetrahedra

La3 B6 O13 (OH) was obtained by a high-pressure/high-temperature experiment at 6 GPa and 1673 K. The compound crystallizes in the space group P21 (no. 4) with the lattice parameters a=4.785(2), b=12.880(4), c=7.433(3) Å, and β=90.36(10)°, and is built up of corner- as well as edge-sharing BO4 tetrahedra. It represents the first acentric high-pressure borate containing these B2 O6 entities. The compound develops borate layers of "sechser"-rings with the La3+ cations positioned between the layers. Single-crystal and powder X-ray diffraction, vibrational and MAS NMR spectroscopy, second-harmonic generation (SHG) and thermoanalytical measurements, as well as computational methods were used to affirm the proposed structure and the B2 O6 entities.

From LiB3 O5 to NaRbB6 O9 F2 : Fluorine-Directed Evolution of Structural Chemistry

Introducing fluorine into borates indicates the direction for structural evolution. A new fluorooxoborate, NaRbB₆ O₉ F₂ featuring a unique [B₆ O₉ F₂ ]_∞ layered structure and excellent optical properties has been synthesized. It is further demonstrated that incorporation of fluorine can enrich the structural chemistry of borates.

NaBaMIIIQ3 (MIII = Al, Ga; Q = S, Se): first quaternary chalcogenides with isolated edge-sharing (MIII2Q6)6− dimers

New series of quaternary chalcogenides with firstly discovered isolated edge-sharing (MIII2Q₆)⁶⁻ dimers showing obvious optical anisotropy were reported.

Synthesis and characterization of Cd4YbO(BO3)3 – a congruent melting cadmium–ytterbium oxyborate with large nonlinear optical properties

A novel ultraviolet nonlinear-optical material Cd₄YbO(BO₃)₃ has been discovered in the CdO–Yb₂O₃–B₂O₃ system.