Oxo boron clusters and their open frameworks

This review article briefly summarizes the recent research advances in the field of crystalline oxo boron clusters and their open frameworks. By using different amine molecules and transition metal complexes or inorganic ions as the charge-balancing agents, different oxo boron clusters, such as [B ₃O₃(OH)₄]^-, [B₄O ₅(OH)₄]^2-, [B₅O₆(OH) ₄]^-, [B₇O₉(OH)₅] ^2-, [B₈O₁₀(OH)₆]^2-, [B₉O₁₂(OH)₆]^3-, and [B ₁₄O₂₀(OH)₆]^4- polyanions, have been successfully isolated and structurally characterized. These polyborate anions may act as the main building blocks to create new open-framework compounds with layered and three-dimensional structures. Odd ring channels and helical channels are noteworthy in open-framework borate structures. Besides their traditional zeolitic properties, open-framework borates exhibit interesting optical properties including photoluminescence and second harmonic generation, suggesting their potential applications in catalysis, nonlinear optics, display and lighting devices.