Zeolitic Open-Framework Borates with Noncentrosymmetric Structures and Nonlinear Optical Properties

Structural characterisation and optical properties of new alkaline earth phosphate CaMg(P4O12) and alkaline alumophosphate Cs3Al4(PO4)5

Two new family members of mixed alkali-earth metal phosphate and aluminophosphate CaMg(P4O12) and Cs3Al4(PO4)5 were prepared from a phosphate system using a high-temperature solution method. The structural analysis results show that two compounds crystallize in the monoclinic space group C2/c and P21/n and feature a three-dimensional (3D) network. The 3D structure of CaMg(P4O12) consists of [CaO6], [MgO6] octahedra and [P4O12] rings, in which the [MgO6] and [P4O12] rings link to form a 3D structure and Ca2+ cations are filled within the structure. Interestingly, for compound Cs3Al4(PO4)5, its structure features 4, 8, and 12-ring channels with [Al2O4O4P2O4], [Al4O8O8P4O8] and [Al6O12O12P6O12] units as BBUs, respectively; the Cs+ cations are located in the cavities. Furthermore, IR spectral analysis and thermal properties are discussed. UV-vis-NIR diffuse reflectance spectroscopy data show that the UV cutoff edges of CaMg(P4O12) are below 200 nm. Remarkably, in order to determine optical properties and the structure-properties relationship, theoretical calculations were adopted. Electronic structure calculations demonstrate that CaMg(P4O12) has an indirect band gap with the value of 5.86 eV, and Cs3Al4(PO4)5 has a direct band gap of 5.21 eV.

Na1.5Cs0.5[Al{BO3}{B9O15(OH)3}1/3]: An Acentric Layered Aluminoborate with Nonlinear-Optical Properties

An acentric aluminoborate (ABO), Na1.5Cs0.5[Al{BO3}{B9O15(OH)3}1/3] (1), has been made under solvothermal conditions. The alternations of AlO4 tetrahedra and BO3 triangles first build up the 2D ABO layer with 6-MR (membered-ring) windows. The fanlike B9O15(OH)3 cluster adorns the layer through Al-O-B linkages, producing a pair of unclosed channels with 7-MR aperture on the lateral side of the layers. The novel B9O15(OH)3 cluster represents the largest oxoboron cluster in the acentric ABO family. 1 not only shows a moderate second-harmonic-generation response of 1.2 times that of potassium dihydrogen phosphate but also has a short cutoff edge below 200 nm, indicating its potential applications in deep-UV regions.

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.

Tailoring Hybrid Aluminoborate Frameworks by Incorporating Multicomponent Cadmium-Amine Complexes with Various Conformations

Inorganic-organic hybrid aluminoborates represent a subclass of porous materials, which rely on effective construction method and structure-directing agents. Herein, we prepared a series of hybrid aluminoborates through covalent decoration of unsaturated Cd²⁺ complexes, whose formation take advantage of chelating amine and long-chain diamine as mixed ligands. These isolated compounds, that is, [Cd(en)(1,4-dab)_0.5][AlB₅O₁₀] (1a; its analogue with discrete complex [Cd(en)(dien)H₂O][AlB₅O₁₀] is denoted as 1b), [Cd(1,2-dap)_1.5(1,4-dabH)_0.5]{Al[B₅O₈(OH)₂](B₅O₁₀)_0.5} (2), and [Cd(en)(1,3-dap)][AlB₅O₁₀] (3) feature open frameworks (1a, 1b, and 3) or a sandwich-like porous layer (2) that are constructed by AlO₄ tetrahedra and [B₅O₁₀]^5-/[B₅O₈(OH)₂]^3- clusters. However, they exhibit different structural features in interconnection, channel environment, and topology as a result of diversified interactions between unsaturated complexes and aluminoborate frameworks, that is, through forming two Cd-O bonds with (i) a pair of neighboring BO₃ and AlO₄, (ii) the same AlO₄, or (iii) the same BO₃. The variation in connection mode exerts essential influence on binding effects and steric hindrance that are reflected by changes in interatomic distance, bond angle, window configuration, and interlinkage of units. In addition, the incorporation of unsaturated Cd²⁺ complexes endows these aluminoborate materials with photoluminescence function. Compound 3 with a noncentrosymmetric structure exhibits second harmonic generation (SHG) response approximately 0.7 times that of KDP. The preparation strategy for hybrid aluminoborates proposed here combines well molecular design with templating assembly, whose synergistic effect would be crucial for drawing a rational pathway for inorganic synthesis, especially with focus on structural and functional innovation.

Two layered galloborates from centric to acentric structures: syntheses and NLO properties

Two layered galloborates (GBOs), Na₃GaB₄O₉ (1) and Na₅Ga[B₇O₁₂(OH)]₂·2B(OH)₃ (2), have been solvothermally made. 1 exhibits an unprecedented layer built by GaO₄ tetrahedra and B₄O₉ clusters. 2 was made by raising the ratio of B/Ga and the reaction temperature of 1, featuring a 2D acentric layer built by GaO₄ groups and B₇O₁₃(OH) clusters. 2 shows the highest second-harmonic generation (SHG) response of 4.6 times that of KDP (KH₂PO₄) among main group metal borates (MBOs).

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.

Li3[Al(PO4)2(H2O)1.5] and Na[AlP2O7]: from 2D layered polar to 3D centrosymmetric framework structures

Two new aluminophosphates with moderate NLO property or a short UV cut-off edge (∼190 nm) are reported.

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.

KBi(IO3)3(OH) and NaBi(IO3)4: from the centrosymmetric chain to a noncentrosymmetric double layer

Two bismuth iodates via tuning of alkali–metal ions reveal a structural transition from the centrosymmetric chain to a non-centrosymmetric double layer.