A Series of Open-Framework Aluminoborates Templated by Transition-Metal Complexes

Two novel metal borates with three-dimensional open-framework layers constructed from [M2B8O20(OH)2] (M = Al, Ga) cluster units

Two novel metal borates, Ba[MB4O8(OH)]·H2O (M = Al/Ga), with a three-dimensional open-framework layer have been synthesized under hydro(solvo)thermal conditions, in which the Al(3+)/Ga(3+) ions have been successfully introduced into the oxoboron cluster backbone and further linked together to form the open-framework layer composed of the [M2B8O20(OH)2] cluster units. The half-unit [MB4O11(OH)] can be viewed as analogous to the known [B5O9(OH)] cluster. Interestingly, the rare M-O-M linkages play a crucial role in forming the open-framework layer.

Systematic study of Cr3+ substitution into octahedra-based microporous aluminoborates

Single crystals of pure aluminoborate PKU-1 (Al3B6O11(OH)5·nH2O) were obtained, and the structure was redetermined by X-ray diffraction. There are three independent Al atoms in the R3 structure model, and Al3 locates in a quite distorted octahedral environment, which was evidenced by (27)Al NMR results. This distortion of Al3O6 octahedra release the strong static stress of the main framework and leads to a symmetry lowering from the previously reported R3 to the presently reported R3. We applied a pretreatment to prepare Al(3+)/Cr(3+) aqueous solutions; as a consecquence, a very high Cr(3+)-to-Al(3+) substitution content (∼50 atom %) in PKU-1 can be achieved, which is far more than enough for catalytic purposes. Additionally, the preference for Cr(3+) substitution at the Al1 and Al2 sites was observed in the Rietveld refinements of the powder X-ray data of PKU-1:0.32Cr(3+). We also systematically investigated the thermal behaviors of PKU-1:xCr(3+) (0 ≤ x ≤ 0.50) by thermogravimetric-differential scanning calorimetry, in situ high-temperature XRD in vacuum, and postannealing experiments in furnace. The main framework of Cr(3+)-substituted PKU-1 could be partially retained at 1100 °C in vacuum. When 0.04 ≤ x ≤ 0.20, PKU-1:xCr(3+) transferred to the PKU-5:xCr(3+) (Al4B6O15:xCr(3+)) structure at ∼750 °C by a 5 h annealing in air. Further elevating the temperature led to a decomposition into the mullite phase, Al4B2O9:xCr(3+). For x > 0.20 in PKU-1:xCr(3+), the heat treatment led to a composite of Cr(3+)-substituted PKU-5 and Cr2O3, so the doping upper limit of Cr(3+) in PKU-5 structure is around 20 atom %.

β-BaGa[B4O8(OH)](H2O) and Ba4Ga[B10O18(OH)5](H2O): new barium galloborates featuring unusual [B4O8(OH)]5− and [B10O18(OH)5]11− clusters

Centrosymmetric β-BaGa[B₄O₈(OH)](H₂O) with a layered structure and polar Ba₄Ga[B₁₀O₁₈(OH)₅](H₂O) with a novel 3D framework structure have been reported.

Incorporating [GaB4O11(OH)]8−clusters to construct luminescent galloborate with open-framework layers

A luminescent 5-connected galloborate with open-framework layers has been obtained under mild hydrothermal conditions by incorporating [GaB₄O₁₁(OH)]⁸⁻clusters.

Two Cu-complex directed aluminoborates: from 2D layers to 3D frameworks

Two novel aluminoborates (1 and 2) containing Cu complexes have been prepared under solvothermal conditions. Both are built from AlO₄ groups and [B₅O_10−n(OH)_n] (n = 0 and 2) clusters. 1 features a 2D aluminoborate layer with 16-member rings, whereas 2 is a 3D framework stacked by different building layers, showing the first Cu-complex directed aluminoborate.

A pillared–layered zincoborate with an anionic network containing unprecedented zinc oxide chains

The first pillared–layered 3D zincoborate framework built by Zn–O–B networks and 1,6-diaminohexane pillars, in which the {Zn₂} and {Zn₆} clusters linked alternately to form zigzag chains and joined by BO₃ units, resulting in 2D networks that were further decorated by B₃O₇H₂ clusters.

Synthesis and structure of QD-6: a novel aluminoborate constructed from unprecedented [B@Al6O24] and polyborate clusters

A novel aluminoborate (NH(4))(6)[C(5)NH(12)](6)[Al(12)B(65)O(105)(OH)(33)]·(H(2)O)(15) (QD-6), has been synthesized under mild hydrothermal conditions and characterized by IR, elemental analysis, TGA, powder and single-crystal X-ray diffractions. This compound crystallizes in the rhombohedral space group R3 (No. 148) with the lattice constants a = 23.7421(2) Å, c = 24.7699(3) Å, V = 12091.9(2) Å(3), and Z = 3. QD-6 consists of two unprecedented aluminoborate clusters, [Al(6)B(34)O(54)(OH)(18)](6-) and [Al(6)B(31)O(51)(OH)(15)](6-), which are built from the same hexagon-like [B@Al(6)O(24)] clusters and [B(11)O(17)(OH)(6)] or [B(10)O(16)(OH)(5)] polyborates.