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

Two mixed alkali- and alkaline-earth metal borates, Na 2 Ca 2 [B 6 O 9 (OH) 4 ]·SO 4 ( 1 ) and KNa 2 [B 6 O 10 ]·HCOO ( 2 ), have been synthesized under solvothermal conditions. 1 features an anionic chain constructed from novel [B 6 O 11 (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 [B 6 O 13 ] 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 KH 2 PO 4 (KDP).