An Ultraviolet Nonlinear Optic Borate with 13-Ring Channels Constructed from Different Building Units

Sr2[B5O8(OH)]2 ⋅ [B(OH)3] ⋅ H2O: A Strontium Borate That Shows Deep-Ultraviolet-Transparent Nonlinear Optical Properties

A new noncentrosymmetric strontium borate, P1-Sr2[B5O8(OH)]2 ⋅ [B(OH)3] ⋅ H2O (1), has been synthesized under the hydrothermal condition. The P1-Sr2[B5O8(OH)]2 ⋅ [B(OH)3] ⋅ H2O shows a layered B-O network with 9-ring windows in the ab plane. Sr2+ cations, H3BO3, and H2O molecules are located in the voids of layers and interlayers, respectively. The P1-Sr2[B5O8(OH)]2 ⋅ [B(OH)3] ⋅ H2O is the first synthetic phase of veatchite, while the other three polymorphs are found in different natural minerals. This strontium borate is a potential deep-ultraviolet-transparent nonlinear-optical (NLO) crystal whose second-harmonic-generation (SHG) intensity is 1.7 times that of KH2PO4 (KDP) and is phase-matchable. The short wavelength cutoff edge of compound 1 is below 190 nm. Density functional theory (DFT) calculations show that the B-O units are responsible for the nonlinear optical property.

Co(II)-doped hybrid Zn(II) tetraborate complexes, [ZnxCo(1-x)(1,3-dap)B4O7] (1,3-dap = 1,3-diaminopropane): BET analysis and N2/H2O/D2O adsorption studies

A series of mono/bimetallic isostructural hybrid tetraborates of the general formula [ZnxCo(1-x)(1,3-dap)B4O7] has been prepared using a solvothermal method. Their adsorption/desorption curves for H2O and D2O demonstrate that these materials have a stronger affinity for H2O than for D2O and enrich the D2O content of D2O/H2O mixtures.

Recent Progress in Crystalline Borates with Edge-Sharing BO4 Tetrahedra

Crystalline borates have received great attention due to their various structures and wide applications. For a long time, the corner-sharing B-O unit is considered a basic rule in borate structural chemistry. The Dy₄B₆O₁₅ synthesized under high-pressure is the first oxoborate with edge-sharing [BO₄] tetrahedra, while the KZnB₃O₆ is the first ambient pressure borate with the edge-sharing [BO₄] tetrahedra. The edge-sharing connection modes greatly enrich the structural chemistry of borates and are expected to expand new applications in the future. In this review, we summarize the recent progress in crystalline borates with edge-sharing [BO₄] tetrahedra. We discuss the synthesis, fundamental building blocks, structural features, and possible applications of these edge-sharing borates. Finally, we also discuss the future perspectives in this field.

Mixed Alkali Metal and Alkaline Earth Metal Scandium Borate Birefringence Material with Layered Structure and Short Ultraviolet Cutoff Edge

Birefringent crystals are essential in the domains of linear and nonlinear optics that need light wave polarization control. Rare earth borate has become a popular study material for ultraviolet (UV) birefringence crystals due to its short cutoff edge in the UV area. RbBaScB₆O₁₂, a two-dimensional layered structure compound with the B₃O₆ group, was effectively synthesized through spontaneous crystallization. The UV cutoff edge of RbBaScB₆O₁₂ is shorter than 200 nm, and the experimental birefringence is 0.139 @ 550 nm. Theoretical research indicates that the large birefringence originates from the synergistic impact of the B₃O₆ group and the ScO₆ octahedron. RbBaScB₆O₁₂ is an outstanding candidate material for birefringence crystals in the UV and even deep UV regions due to its short UV cutoff edge and significant birefringence.

Na4[B6O9 (OH)3](H2O) Cl: A Deep-Ultraviolet Transparent Nonlinear Optical Borate Chloride with {[B6O9 (OH)3]3-}∞ Chains

The development of nonlinear-optical (NLO) crystals with short ultraviolet cutoff edges is significant and challenging. Here, a new sodium borate chloride, Na₄[B₆O₉ (OH)₃](H₂O) Cl, was successfully obtained by the mild hydrothermal method, which crystallizes in a polar space group Pca2₁. The structure of the compound is characterized by {[B₆O₉ (OH)₃]^3-}_∞ chains. Measurements of optical properties indicate the compound exhibits a deep-ultraviolet (DUV) cutoff edge (≤200 nm) and moderate second harmonic generation response (0.4 × KH₂PO₄). It presents the first DUV hydrous sodium borate chloride NLO crystal and the first sodium borate chloride possessing a one-dimensional B-O anion framework. Probing into the connection of structure and optical properties has been performed based on theoretical calculations. These results are instructive for designing and obtaining new DUV NLO materials.

Structural Regulation and Oxygen Reduction Reaction Activity of [Co(bpy)2BO2(OH)] and [Cu(bpy)(OH)]2- Complex Templated Borates

Two templated borates, [Co(bpy)₂BO₂(OH)]·[B₅O₆(OH)₄]·H₃BO₃·H₃O·H₂O (1) and [Cu(bpy)(OH)]₂·[B₅O₆(OH)₄]₂·H₂O (2), have been synthesized successfully and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and Fourier transform infrared. The [Co(bpy)₂BO₂(OH)] complex in 1 shows a very rare coordination mode between Co²⁺ and BO₂(OH)^2-. The structures of 1 and 2 can be adjusted by changing the reagent. The oxygen reduction reaction activity of these Co- and Cu-based catalysts was studied. The E_1/2 values of Co-C-750 and Cu-C-750 are 0.864 and 0.837 V, respectively.

Two Acentric Aluminoborates Incorporated d10 Cations: Syntheses, Structures, and Nonlinear Optical Properties

Two acentric aluminoborates (ABOs), [Zn(en)₂Al{B₅O₉(OH)}{BO(OH)₂}] (1) and [Cd(en)₂AlB₅O₁₀]·H₂O (2) (en = ethylenediamine), have been solvothermally made. 1 includes a two-dimensional (2D) wavy ABO layer using B₅O₉(OH) clusters and AlO₃{BO(OH)₂} groups, in which both units can be regarded as three-connected nodes, and simplifying the ABO layer to a hcb-type network. 2 features an acentric three-dimensional (3D) porous framework with a unique unc-type network constituted by strictly alternating connected B₅O₁₀ clusters and AlO₄ units. The structural transformation from a 2D layer 1 to a 3D framework 2 was achieved with the elimination of the terminal hydroxyls in layer 1 by adjusting synthetic conditions in the same solvent system. Metal-amine complexes Zn(en)₂/Cd(en)₂ bond to the inorganic walls and are located in the cavity of frameworks 1 and 2, respectively. Compounds 1 and 2 exhibit large second-harmonic generation (SHG) responses that are 2.2 and 2.7 times those of KH₂PO₄ (KDP), respectively, which are among the largest powder SHG responses for all deep-ultraviolet (deep-UV) ABOs. The UV-vis diffuse reflectance spectra of 1 and 2 show a wide transparency window below 190 nm. Density functional theory (DFT) calculations indicate that the B-O units and the introduced distorted d¹⁰ metal polyhedra played a decisive role in the optical properties of both compounds.

Noncentrosymmetric versus Centrosymmetric: Halogen Induced Variable Coordination Modes of Sn2+ and Structural Transition in Sn3B3O7X (X = Cl and Br)

Two new borate halides, Sn₃B₃O₇X (X = Cl and Br), were successfully synthesized via introducing Sn²⁺ with lone-pair and halogen into borate. Interestingly, halogen-induced variable coordination modes of Sn²⁺ and anion frameworks make them crystallize in different space groups, from noncentrosymmetric (Pna2₁) to centrosymmetric (Pbca). Sn₃B₃O₇Cl possesses an SHG response of about 0.5 times that of KDP, while Sn₃B₃O₇Br exhibits a large birefringence (0.123@1064 nm). The theoretical calculations were performed to elucidate the structure-property relationships.

Double-Modification Oriented Design of a Deep-UV Birefringent Crystal Functionalized by [B12 O16 F4 (OH)4 ] Clusters

Polarization modulation of deep-UV light is of significance to current technologies, and to this end, the birefringent crystal has emerged as an invaluable material as it allows for effective light modulation. Herein, a double-modification strategy driven by F and OH anions that makes double effects towards the critical property enhancement of deep-UV birefringent crystals is proposed. This leads to a new hydroxyborate (NH₄ )₄ [B₁₂ O₁₆ F₄ (OH)₄ ] with giant cluster as a deep-UV birefringent crystal with large birefringence (Δn_exp. =0.12@546.1 nm). This birefringence is a record among inorganic hydroxyborates with experimentally measured birefringence. Structural analysis shows that the near-plane arrangement of [B₁₂ O₁₆ F₄ (OH)₄ ] cluster is responsible for the large optical anisotropy. Theoretical calculations indicate that its π-conjugated [BO₃ ] and [BO₂ OH] units are the main source of this large optical anisotropy.

Ba2B10O16(OH)2·(H3BO3)(H2O): A Possible Deep-Ultraviolet Nonlinear-Optical Barium Borate

A new acentric barium borate, Ba₂B₁₀O₁₆(OH)₂·(H₃BO₃)(H₂O) (1), was synthesized via a hydrothermal process. Compound 1 contains two different boron oxide units of [B₅O₁₀(OH)]^6- anions and H₃BO₃ molecules and features 9-ring channels along the c axis in a layered structure. This barium borate is a possible deep-ultraviolet nonlinear-optical crystal for its moderate second-harmonic-generation signal and wide transparency window below 190 nm.

Two Indium Iodate-Nitrates with Large Birefringence Induced by Hybrid Anionic Functional Groups and Their Favorable Arrangements

Two new indium iodate-nitrates, In(IO₃)₂(NO₃) (1) and [In(IO₃)(OH)(H₂O)](NO₃) (2), were rationally designed through the integration of hybrid anionic functional units. They exhibit large birefringences (1, 0.269; 2, 0.188, at 532 nm) and wide band gaps (1, 4.08 eV; 2, 4.39 eV), which is attributed to the synergistic effect of two types of birefringence-active units, namely, lone-pair IO₃ and π-conjugated NO₃ anionic groups. Through the substitution of OH and H₂O of 2 with IO₃, the hydrogen bonds of 2 are eliminated and the birefringence of 1 is greatly enhanced, highlighting the intriguing role of isovalent substitution in the discovery of fascinating optical materials.

Na3B6O10(HCOO): an ultraviolet nonlinear optical sodium borate-formate

A new sodium borate-formate, which displays a pcu-type open framework and ultraviolet nonlinear optical properties, has been synthesized under surfactant-thermal conditions.

Sr3B14O24: a new borate with a [B14O30] fundamental building block and an unwonted 2D double layer

A new alkaline-earth metal borate, Sr₃B₁₄O₂₄, was successfully synthesized by a high-temperature solution method. It crystallizes in the monoclinic space group P2₁/c (no. 14) and features a fundamental building block (FBB) [B₁₄O₃₀] which is composed of eight [BO₃] and six [BO₄] units. The FBBs further condense to form an unwonted infinite 2D double layer extended in the bc plane. The UV-Vis-NIR diffuse reflectance spectrum shows that the cutoff edge of Sr₃B₁₄O₂₄ is less than 200 nm, which indicates its potential use in the deep UV region. In addition, the first principles theoretical study was carried out to better understand the relationship between the structure and performance.

LiB9O15·H2dap·H2O: A Cotemplated Acentric Layer-Pillared Borate Built by Mixed Oxoboron Clusters

An acentric layer-pillared borate, LiB₉O₁₅·H₂dap·H₂O (1, dap = 1,3-diaminopropane), cotemplated by organic and inorganic cations and build by mixed oxoboron cluster units of B₆O₁₃^8- and B₃O₇^5-, has first been made under solvothermal conditions, in which the B₆O₁₃^8- clusters link each other to form 2D layers containing 9-membered ring (MR) windows, while the B₃O₇^5- clusters join together to produce 1D chains that further perform as the pillars to connect neighboring layers, resulting in a 3D layer-pillared framework with 13- and 7-MR channels located by H₂dap²⁺ and Li⁺ cations, respectively. Its second harmonic generation shows a response of ∼2.1 times that of KDP (KH₂PO₄).

K2 Na3 [{B6 O10 (OH)}{B3 O4 (OH)3 }] ⋅ H2 O: A Layered Borate Built by Mixed Oxoboron Clusters with Nonlinear-Optical Property

A new acentric borate, K₂ Na₃ [{B₆ O₁₀ (OH)}-{B₃ O₄ (OH)₃ }] ⋅ H₂ O (1) has been made under solvothermal condition. 1 has layered structure made by B₆ O₁₃ (OH)-based chains and B₃ O₅ (OH)₃ -bridging clusters. Second-harmonic generation (SHG) measurements reveal that 1 is a phase-matchable nonlinear optical (NLO) material, showing the SHG signal intensity of 1.8 times that of KDP (KH₂ PO₄ ). Besides, UV-Vis diffuse reflectance spectrum shows that 1 has the short deep UV (DUV) absorption cutoff edge of 198 nm. Thermogravimetric analysis reveals it has good thermal stability. Also 1 represents firstly mixed oxoboron clusters-made 2D layered borate with NLO property.

Li3La2(BO3)3 and Li1.75Na1.25La2(BO3)3: A Great Enhancement in Birefringence Induced by Optimal Arrangement of π-Conjugated [BO3] Units

In virtue of the essential role in controlling polarized light, outstanding ultraviolet (UV) and deep-ultraviolet (DUV) birefringent crystals are imperative in many advanced optical instruments. To design the UV and DUV crystals with large birefringence, we paid more attention to combining the excellent gene, π-conjugated [BO₃] unit and metal cations beneficial to blue-shift the cutoff edge; finally, two rare-earth borates Li₃La₂(BO₃)₃ and Li_1.75Na_1.25La₂(BO₃)₃ have been synthesized using the high-temperature solution method. Compared with Na₃La₂(BO₃)₃, Li₃La₂(BO₃)₃ and Li_1.75Na_1.25La₂(BO₃)₃ are isostructural, and the isolated [BO₃] units are arranged nearly parallel to each other in the structure, which is conducive to generating a larger birefringence. The structural comparison between the two crystals and Na₃La₂(BO₃)₃ indicates that the various coordination environments of alkali metal cations play an important role in the evolution of the crystal structure from Li₃La₂(BO₃)₃ and Li_1.75Na_1.25La₂(BO₃)₃ to Na₃La₂(BO₃)₃. This work can contribute to a better understanding of the enhancement in birefringence from Na₃La₂(BO₃)₃ (0.023 @ 1064 nm) to Li₃La₂(BO₃)₃ (0.078 @ 1064 nm) with the perspective of structure-property relationships. Meanwhile, the two title crystals possess the DUV cutoff edge (<190 nm), suggesting that they can be applied as the DUV birefringent crystals.

Two Chiral Metal Complex Templated Aluminoborates Constructed from Three Types of Oxoboron Clusters

The two acentric aluminoborates (ABOs) [M(dap)₃]₂{Al[B₅O₇(OH)₃][B₅O₈(OH)₂][B₆O₉(OH)₂]} (M and dap represent Co(1)/Ni(2) and 1,2-diaminopropane, respectively) templated by chiral metal complexes (CMCs) have been solvothermally synthesized. The isostructural 1 and 2 crystallize in the chiral space group P2₁. Both feature unprecedented 2D wavelike layers built by three kinds of oxoboron (B-O) clusters ([B₅O₇(OH)₃]^2-, [B₅O₈(OH)₂]^3-, and [B₆O₉(OH)₂]^2-) and AlO₄ tetrahedra. In the frameworks of 1 and 2, AlO₄ and [B₆O₉(OH)₂]^2- units are strictly alternating into 1D chains. Further, [B₅O₈(OH)₂]^3- clusters link adjacent chains to form 2D wavelike layers. In addition, the [B₅O₇(OH)₃]^2- units as the hanging clusters are supported on two sides of the wavelike layers through AlO₄ groups, resulting in the first example of a wavelike layer ABO composed of three kinds of B-O clusters and four types of channels. 1 and 2 display second-harmonic generation (SHG) signals about ∼1.3 and ∼0.93 times that of KH₂PO₄ (KDP) and belong to the class of wide-band-gap semiconductors.

Al8(BO3)4(B2O5)F8: A F-Containing Aluminum Borate Featuring Two Types of Isolated B-O Groups

Al₈(BO₃)₄(B₂O₅)F₈, as a new aluminum borate fluoride, has been synthesized by the high-temperature reaction with the closed system for the first time. With respect to its structure, the isolated BO₃ and B₂O₅ groups reside in the center and edge of tunnels constructed by the AlO₄F₂ polyhedra. The AlO₄F₂ polyhedra play the vital role on the formation of isolated B-O groups. According to our investigation, Al₈(BO₃)₄(B₂O₅)F₈ is the first case, which features two types of independently isolated B-O groups in the aluminum borate fluorides. Its cutoff edge is up to deep ultraviolet (DUV) range. What is more, the energy dispersive spectroscopy (EDS), infrared (IR) spectrum, and the first-principles calculations of Al₈(BO₃)₄(B₂O₅)F₈ have been performed.

Rb3BaTeB7O15: a novel [B7O16] fundamental building block in a new telluroborate with [TeO3] polyhedra

A new telluroborate Rb₃BaTeB₇O₁₅ with a new [B₇O₁₆] fundamental building block has been synthesized, and it is the first telluroborate that is constructed only by using [TeO₃] polyhedra.

Trinuclear Cd3O14 hexaborate and two nickel borates based on molten salt synthesis and precursor synthesis: structure, characterization, and properties

In this work, different synthetic methods were used to prepare metal borates. One cadmium borate Cd3[B6O9(OH)2]2·2NO3·4H2O (1) and two nickel borate Ni0.8Mn0.2{B6O7(OH)3[O(CH2)2NH2]3} (2), [Ni(1-MI)6]·[B5O6(OH)4]2·2DMF (3, 1-MI = 1-methylimidazole, DMF = N,N-dimethylformamide) species were successfully prepared. The structures of these three compounds were confirmed via single crystal powder X-ray diffraction (SCPXRD), elemental analysis, FTIR, PXRD, and ICP studies. Compound 1 was prepared via molten salt synthesis, and compounds 2 and 3 were prepared via precursor synthesis, which is a synthetic method that uses a certain polyanionic cluster as a reagent. Compound 1 shows a novel three-dimensional (3D) structure, in which the [B6O11(OH)2] units acting as the basic polyanionic cluster form a two-dimensional (2D) anionic structure. In addition, the unexpected Cd3O14 clusters are connected with the 2D structures, leading to the 3D structure. The crystal structure of 2 is packed with very large neutral Ni0.8Mn0.2{B6O7(OH)3[O(CH2)2NH2]3} oxo-metal-boron clusters. The crystal structure of 3 consists of a [B5O6(OH)4]- cluster, a DMF molecule, and a [Ni(1-MI)6]2+ complex. In particular, 2 was successfully constructed using the same hexaborate cluster as its precursor. However, 3 only contains Ni2+ cations when a neutral NixMn1-x[B6O7(OH)6] cluster was used as an initial reagent, and it shows an ability to select a certain metal cation during the self-assembly process. Moreover, compounds 1, 2, and 3 exhibit different wide band gaps of 3.06 eV (1), 3.95 eV (2), and 4.24 eV (3).

K2[B4O5(OH)4]·H2O and K2[B4O5(OH)4]: two new hydrated potassium borates with isolated [B4O5(OH)4]2− units and different structural frameworks

Two new hydrated potassium tetraborates with isolated [B₄O₅(OH)₄]²⁻ units were obtained via a mild hydrothermal method.

Li2Na2[B12O19(OH)2]: a new open framework borate with a pcu-type net constructed from large cyclic dodeca-oxoboron units

A new open-framework borate with a pcu-type net has been made under solvothermal conditions by incorporating large cyclic dodeca-oxoboron clusters.

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.

Linking 1D Transition-Metal Coordination Polymers and Different Inorganic Boron Oxides To Construct a Series of 3D Inorganic-Organic Hybrid Borates

Three inorganic-organic hybrid borates, M(1,4-dab)[B₅O₇(OH)₃] [M = Zn (1), Cd (2), 1,4-dab = 1,4-diaminobutane)] and Co(1,3-dap)[B₄O₇] (3, 1,3-dap = 1,3-diaminopropane), which integrated characteristics of 1D coordination polymers and 1D/3D inorganic boron oxides have been obtained under solvothermal conditions. Compounds 1 and 2 are isostructural and crystallize in a centrosymmetric space group P2₁/c; the 3D achiral structures of 1 and 2 consist of the nonhelical Zn/Cd-1,4-dap coordination polymers and 1D B-O chains. Compound 3 crystallizes in a chiral space group P4₃2₁2; the helical Co-1,3-dap coordination polymer chains are entrained within a 3D B-O network and finally form the chiral framework. Compounds 1-3 represent good examples of using coordination polymers to construct mixed-motif inorganic-organic hybrid borates. Compounds 1 and 2 display blue luminescence when excited with UV light.

Ion-induced structural and optical performance evolution in LBO-like crystals: experimental and theoretical investigation

A new alkali metal borate fluoride Li₃KB₉O₁₅F has been obtained for the first time with a UV cut-off edge below 175 nm.

NH4B11O16(OH)2: a new ammonium borate with wavy-shaped polycyclic 2∞[B11O16(OH)2] layers

The ammonium borate NH₄B₁₁O₁₆(OH)₂ has been successfully synthesized by a mild hydrothermal method.

Low-temperature-flux syntheses of ultraviolet-transparent borophosphates Na4MB2P3O13 (M = Rb, Cs) exhibiting a second-harmonic generation response

The first non-centrosymmetric mixed-alkali-metal borophosphates, Na₄MB₂P₃O₁₃ (M = Rb 1, Cs 2), were obtained using a low-temperature flux method. Single-crystal X-ray diffraction studies of 1 and 2 reveal that the two compounds are isostructural, both crystallizing in the orthorhombic space group Pna2₁; their structures consist of novel 1D borophosphate chains constructed from B₂P₃O₁₄ fundamental building units, assembled into a 3D framework by alkali metal cations. Second-harmonic generation (SHG) measurements show that 1 and 2 are type-I phase-matchable, with SHG responses ca. 0.35 and 0.42 times that of KH₂PO₄, respectively. The cut-off edges of 1 and 2 are ca. 276 and 267 nm, respectively, which suggests that they are potential ultraviolet nonlinear optical materials. Density functional theory calculations were employed to shed light on the band structure and density of states as well as the electron density distribution.