Na_1.5Cs_0.5[Al{BO₃}{B₉O₁₅(OH)₃}_1/3]: An Acentric Layered Aluminoborate with Nonlinear-Optical Properties

An acentric aluminoborate (ABO), Na_1.5Cs_0.5[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.