Design and Synthesis of a Series of Novel Mixed Borate and Carbonate Halides.

Combining different functional units together has been regarded as the most ideal strategy to design and synthesize new inorganic materials. Based on numerous experiments, it was possible to assemble three kinds of anion groups together and find a series of novel mixed borate and carbonate halides, Rb9 [B4 O5 (OH)4 ]3 (CO3 )X⋅7 H2 O (X=Cl, Br, and I) and K9 [B4 O5 (OH)4 ]3 (CO3 )X⋅7 H2 O (X=OH and I). Based on the structural template of these compounds, we also obtained the NaRb6 [B4 O5 (OH)4 ]3 X (X=OH, I) crystals through replacement of the CO3 group with the NaO6 octahedron, which results in the crystal structural changes from P6‾ 2c to R32. In addition, it has been confirmed that the replacement of the CO3 group by the alkali cation has an influence on the band gaps, according to the experimental results and theoretical calculations. Meanwhile, millimeter-scale crystals of Rb9 [B4 O5 (OH)4 ]3 (CO3 )I⋅7 H2 O, K9 [B4 O5 (OH)4 ]3 (CO3 )I⋅7 H2 O, K9 [B4 O5 (OH)4 ]3 (CO3 )OH⋅7 H2 O and NaRb6 [B4 O5 (OH)4 ]3 OH were also obtained after adjusting their growing conditions.