Further Examples of the P‐O‐P Connection in Borophosphates: Synthesis and Characterization of Li2Cs2B2P4O15, LiK2BP2O8, and Li3M2BP4O14 (M=K,Rb)

A new series of anhydrous mixed alkali‐metal borophosphates—Li₂Cs₂B₂P₄O₁₅ ( 1 ), LiK₂BP₂O₈ ( 2 ), Li₃K₂BP₄O₁₄ ( 3 ), and Li₃Rb₂BP₄O₁₄ ( 4 )—have been successfully synthesized by using the conventional solid‐state reaction method. Compound 1 contains a novel fundamental building unit (FBU), B₄P₈O₃₀], with B/P=1:2. Compound 2 contains an FBU of B₂P₄O₁₆] with B/P=1:2. Compounds 3 and 4 are isotypic, and they have a B(P₂O₇)₂] unit as their FBU. In all four compounds, their FBUs are connected through corner sharing to generate layered anionic partial structures, and then further linked with metallic polyhedra to form three‐dimensional (3D) frameworks. Most interestingly, three of the four compounds contain direct P‐O‐P connections in their structures, which is extremely rare among borophosphates. Thermal analyses, IR spectroscopy, and UV/Vis/near‐IR diffuse reflectance spectroscopy have also been performed on the four title compounds.