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

PbTeB4O9: a lead tellurium borate with unprecedented fundamental building block [B4O10] and large birefringence

Herein, the first lead tellurium borate, PbTeB4O9, with an unprecedented fundamental building block [B4O10] was successfully synthesized. The near-parallel alignment of [B4O10] groups and [TeO3] polyhedra resulted in a high birefringence (0.099@1064 nm). The structure-property relationship was discussed by using the first-principles calculations.

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.

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.

Discovery of SrZn2B6O12 with an unprecedented quadruple-layered configuration

A new borate, SrZn2B6O12, is found to show a quadruple-layered configuration. This rare quadruple-layer is stacked by two 2[Zn2B6O12]∞ double-layers that are constructed by two single-layers of 2[B4O7]∞ and 2[Zn2B2O4]∞.

Two New Nonaborates with {B9} Cluster Open-Frameworks and Short Cutoff Edges

Two new nonaborates, Na₂Ba_0.5[B₉O₁₅]·H₂O (1) and Na₄Ca_1.5[B₉O₁₆(OH)₂] (2), have been solvothermally made with mixed alkali and alkaline-earth metal cationic templates. 1 and 2 are constructed by two different types of nonaborate clusters. In 1, the [B₉O₁₉]¹¹⁻ cluster is composed of three corner-sharing [B₃O₇]⁵⁻ clusters, of which two of them interconnect to the 1D B₃O₇-based chains and are further bridged to the 3D framework with 7 types of 10-MR channels by another [B₃O₇]⁵⁻ bridging cluster. The [B₉O₁₈(OH)₂]¹¹⁻ cluster in 2 is made of four BO₄-sharing [B₃O₈]⁷⁻ clusters. As a 4-connected node, the interconnections of [B₉O₁₈(OH)₂]¹¹⁻ construct the unpreceded 2D layer with large 14-MR windows, which are further joined by H-bonds to the 3D supramolecular framework. UV–Vis absorption spectra reveal that both 1 and 2 have short cutoff edges below 190 nm, exhibiting bandgaps of 6.31 and 6.39 eV, respectively, indicating their potential applications in deep UV (DUV) regions.

Two Mixed Alkali-Metal Borates Templated from Cations to Clusters

Two mixed alkali-metal borates, K_0.5Li[B₆O₁₀]·0.5H₃O (1) and [(μ₅-OH)@(Na₄Li)]_0.5[B₆O₁₀]·0.5B(OH)₃ (2), have been prepared under solvothermal conditions. Both of them are obtained in the same synthetic system and contain a B₆O₁₃^8- cluster as the structural-building unit (SBU) but exhibit quite different structural features. 1 is a centric three-dimensional (3D) oxoboron (B-O) framework, where templated mixed K⁺ and Li⁺ cations occupied the cavities of the structure. 2 crystallizes in an acentric space group under the templating effect of a unique acentric alkali-metal cluster [(μ₅-OH)@(Na₄Li)]⁴⁺. The SBU of 2 is also the B₆O₁₃^8- cluster, which acts as six-connected nodes linked together to form a 3D B-O framework, showing different characters from 1 because of two types of templates; the acentric [(μ₅-OH)@(Na₄Li)]⁴⁺ clusters and the electroneutral B (OH)₃ groups fill in two different cages in the framework and further connect each other via Na-O-B bonds to build a novel two-dimensional (2D) wavy bricklike network, resulting in a 3D B-O framework interpenetrated by a 2D [(μ₅-OH)@(Na₄Li)]-B(OH)₃ network. As a crystal material with an acentric space group, 2 shows a good second harmonic generation response of about 2.8 times that of KDP (KH₂PO₄) and has a cutoff edge below 190 nm, which suggests that 2 is a potential deep-UV NLO material.

Syntheses, structures and optical properties of two B3O7 cluster-based borates

1 is a 2D fluctuant layered borate made from two different B3O7 clusters. 2 features a 3D open framework with large 17-MR channels filled with Li-BO(OH)2-Ca chains.