Na₃[Al₂B₆P₄O₂₂(OH)₃](H₂O)₆ and Na₃[Al₂BP₂O₁₁](H₂O)_0.5: Two Remarkable Complex Aluminum Borophosphates

Abstract

Two remarkable aluminum borophosphates (AlBPOs), namely, Na 3 [Al 2 B 6 P 4 O 22 (OH) 3 ](H 2 O) 6 (denoted as ABPO1) and Na 3 [Al 2 BP 2 O 11 ](H 2 O) 0.5 (denoted as ABPO2), have been designed and prepared by low-temperature flux syntheses. The exceptional open framework structure of ABPO1 is formed by a unique microanionic network [Al 2 B 6 P 4 O 22 (OH) 3 ] n 3−, which contains three types of 8-, 12-, and 16-membered ring (MR) tunnels. Interestingly, these tunnels are featured by a type of supernanocage as large as ∼1.753 nm × 1.753 nm × 1.753 nm, which is the first example of AlBPOs containing extra-large cages. Importantly, it was found that Na + can be partially exchanged by K + , Sr 2+ , Cd 2+ , and Ni 2+ , which means that it is a potential ionic exchanger for removing radionuclides and toxic cations. The structure of ABPO2 features a unique 2D anionic AlBPO layer composed of corner-sharing AlO 6 octahedra and AlO 4 , BO 4 , and PO 4 tetrahedra. To the best of our knowledge, this is the first example of both AlO 6 octahedra and AlO 4 tetrahedra being contained in the structure. 9-MRs can be observed along the b-axis. Herein, the syntheses and topological structures of ABPO1 and ABPO2 as well as elemental analysis, thermal stability, infrared spectroscopy, UV−vis diffuse reflectance, structural properties, and ionic exchange properties are also discussed.