Structural Design of Two Fluorine-Beryllium Borates BaMBe2(BO3)2F2 (M = Mg, Ca) Containing Flexible Two-Dimensional [Be3B3O6F3]∞ Single Layers without Structural Instability Problems.

Molecular structural design is a compelling strategy to develop new compounds and optimize the crystal structure by atomic-scale manipulation. Herein, two fluorine-beryllium borates, BaMgBe2(BO3)2F2 and BaCaBe2(BO3)2F2, have been rationally designed to overcome the structural instability problems of Sr2Be2B2O7 (SBBO). When relatively large Ba atoms were introduced, the [Be6B6O15]∞ double layers of SBBO were successfully broken, generating flexible [Be3B3O6F3]∞ single layers. Also, the strategy adopted in this work has many implications in understanding the structural chemistry and designing novel optical functional materials in a beryllium borate system.