Two novel 3D borates: porous-layer and layer-pillar frameworks

摘要

Two new borates, NaK1.5[B{B5O9(OH)}{B5O8(OH)(2)}(1/2)] (1) and Na-3.5[Al{B3O6(OH)}{B5O10}(1/2){BO(OH)}] (2), have been made by a solvothermal method. Structure 1 is made of two types of oxoboron clusters ([B5O9(OH)](4-) and [B5O8(OH)(2)](3-)) and BO4 tetrahedra to form a 3D porous layer, in which the [B5O9(OH)](4-) clusters are bridged by BO4 groups to produce a 2D B-O layer with 11-membered ring (MR) windows, while the [B5O8(OH)(2)](3-) clusters as 2-connected pillars join the adjacent B-O layers to make a 3-D porous layer. Structure 2 is built from two types of oxoboron clusters ([B3O6(OH)](4-) and [B5O12](9-)), AlO4 units and BO2(OH) triangles to produce 3D pillar-layered aluminoborate (ABO), in which the [B5O12](9-) clusters are linked together to form a 2-D B-O layer; the [B3O6(OH)](4-) clusters and AlO4 groups join each other to form 1D tubular ABO; and the BO2(OH) triangles act as linkers to connect the adjacent B-O layer and the ABO tubes, resulting in 3D pillar-layered ABO. Interestingly, the ABO tubes decorated with the BO2(OH) triangles act as pillars to make a 3D layer-pillared structure. UV-vis diffuse spectra indicate that both have cut-off edges below 190 nm, and the calculated band gaps are 5.75 and 5.78 eV, respectively.