Mg(HO)BO(OH)(HO): a new hydrated borate with a short DUV cutoff edge.

A new hydrated magnesium borate, Mg(H2O)6B4O5(OH)4(H2O)3, was synthesized successfully by a facile slow evaporation method. Its structure was determined by single crystal X-ray diffraction, and it contains the functional building block (FBB) [B4O5(OH)4]. It possesses a short DUV cutoff edge (<175 nm) which benefits from the absence of dangling bonds in the crystal structure. Its properties were analyzed by IR spectroscopy and UV-vis-NIR diffuse reflectance spectroscopy. Moreover, theoretical calculations were carried out to analyze the relationship between the electronic structure and optical properties.