Two porous-layered borates built by B7O13(OH) clusters and AlO4/GaO4 tetrahedra

Abstract

Two three-dimensional (3D) porous-layered borates, Na_0.5K_2.5[AlB₇O₁₃(OH)]·H₂O (1) and NaKCs[GaB₇O₁₃(OH)]·1.5H₂O (2), have been obtained under solvothermal conditions. Compound 1 crystallizes in the triclinic space group P, while 2 crystallizes in the monoclinic space group P2₁/n. Compounds 1 and 2 contain similar units of B₇O₁₃(OH) and AlO₄/GaO₄; the strict alternations of B₇O₁₃(OH) clusters and AlO₄/GaO₄ resulted in 3D open-framework layers with 8-R and 13-R channels along different directions. The shapes and orientations of the channels of 1 and 2 are different due to their different space groups. It's interesting to note that three different alkali metal ions (Na⁺, K⁺, and Cs⁺) are found in different positions in 2. UV-vis diffuse reflectance analysis indicates that both compounds show a wide transparency range with a short-wavelength absorption edge below 190 nm.