A novel open-framework with non-crossing channels in the uranyl vanadates A(UO2)4(VO4)3 (A=Li, Na)

Abstract

A new sodium uranyl vanadate Na(UO2)4(VO4)3 has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. It crystallizes in the tetragonal symmetry with space group I41/amd and following cell parameters: a=7.2267(4) Å and c=34.079(4) Å, V=1779.8(2) Å3, Z=4 with ρmes=5.36(3) g/cm3 and ρcal=5.40(2) g/cm3. A full-matrix least-squares refinement on the basis of F2 yielded R1=0.028 and wR2=0.056 for 52 parameters with 474 independent reflections with I⩾2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a CCD detector. The crystal structure is characterized by ∞2[(UO2)2(VO4)] sheets parallel to (001) formed by corner-shared UO6 distorted octahedra and V(2)O4 tetrahedra, connected by V(1)O4 tetrahedra to ∞1[UO5]4− chains of edge-shared UO7 pentagonal bipyramids alternately parallel to the a- and b-axis. The resulting three-dimensional framework creates mono-dimensional channels running down the a- and b-axis formed by face-shared oxygen octahedra half occupied by Na. The powder of Li analog compound Li(UO2)4(VO4)3 has been synthesized by solid-state reaction. The two compounds exhibit high mobility of the alkaline ions within the two-dimensional network of non-intersecting channels.