Two {B 6 }-Based Borates: From 1D Chain to 3D Framework

Two mixed alkali- and alkaline-earth metal borates, Na2Ca2[B6O9(OH)4]·SO4 (1) and KNa2[B6O10]·HCOO (2), have been synthesized under solvothermal conditions. 1 features an anionic chain constructed from novel [B6O11(OH)4]8– clusters, which are linked by the hydrogen bond to form a supramolecular framework. 2 exhibits a 3D open-framework built from bowl-shaped [B6O13]8– clusters and contain interwoven 9-membered ring channels extending along three directions within K+, Na+, and HCOO– ions selectively accommodated, respectively. UV–vis diffuse reflectance spectra reveal that both compounds have ultraviolet absorption cutoff edges. Notably, 2 exhibits a moderate second-harmonic-generation response, with an intensity approximately 1.4 times that of KH2PO4 (KDP).