Na3[Al2B6P4O22(OH)3](H2O)6 and Na3[Al2BP2O11](H2O)0.5: Two Remarkable Complex Aluminum Borophosphates

Two remarkable aluminum borophosphates (AlBPOs), namely, Na3[Al2B6P4O22(OH)3](H2O)6 (denoted as ABPO1) and Na3[Al2BP2O11](H2O)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 [Al2B6P4O22(OH)3]n3-, which contains three types of 8-, 12-, and 16-membered ring (MR) tunnels. Interestingly, these tunnels are featured by a type of super-nanocage 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+, Sr2+, Cd2+, and Ni2+, 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 AlO6 octahedra and AlO4, BO4, and PO4 tetrahedra. To the best of our knowledge, this is the first example of both AlO6 octahedra and AlO4 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.

CsSc[B2P3O11(OH)3]: A New Borophosphate Oligomer Containing Boron in Three- and Fourfold Coordination

CsSc[B2P3O11(OH)3] was obtained by hydrothermal synthesis and represents the first alkali-metal scandium borophosphate containing boron with coordination numbers 3 and 4. The crystal structure was determined from single-crystal X-ray data: orthorhombic, space group Pnna (No. 52), a=13.0529(15) A, b=18.3403(17) A, c=10.3838(12) A, Z=8. The crystal structure contains the oligomeric unit [B2P3O11(OH)3]4- in which a central borate tetrahedron is open-branched by two (OH)PO3 tetrahedra and cyclobranched by one PO4 tetrahedron and a trigonal-planar (OH)BO2 by sharing common apexes. The borophosphate oligomers together with the ScO6 octahedra are condensed to form layers. Simultaneous difference thermal analysis and thermogravimetry revealed the stepwise decomposition of the compound in the temperature range between 333 and 973 K. Partly dehydrated samples do not show any substantial rehydration behavior. The crystal structure of CsSc[B2P3O11(OH)3] is discussed in connection with structural motifs of related borates and borophosphates.