Two Acentric Borates with 2-/3-D Frameworks: Syntheses, Structures, and Nonlinear Optical Properties

Two alkali and main group metal borates, K 3 [B 5 O 8 (OH)]·HCOO ( 1 ) and Al[B 5 O 10 ]·2NH 2 (CH 3 ) 2 ( 2 ), have been synthesized under solvothermal conditions. 1 features a 2D layer constructed from [B 5 O 10 (OH)] 6– clusters, which are linked by hydrogen bonds to form a 3D supramolecular framework. 2 exhibits a 3D aluminoborate framework formed by [B 5 O 10 ] 5– clusters, and strict alternation of B–O clusters and AlO 4 tetrahedra leads to six types of channels. Notably, 3D open-framework 2 is structurally related to the 2D-layered structure of 1, involving terminal dehydroxylation and the introduction of chiral AlO 4 units into the B–O network. Both 1 and 2 exhibit short deep ultraviolet (DUV) absorption cutoff edges and moderate second harmonic generation (SHG) responses of 2.0 and 1.5 times that of KDP, respectively, indicating their potential as DUV nonlinear optical (NLO) crystals.