Co0.50VOPO4·2H2O

The crystal structure of cobalt vanadophosphate dihydrate {systematic name: poly[diaqua-μ-oxido-μ-phosphato-hemi­cobalt(II)vanadium(II)]}, Co0.50VOPO4·2H2O, shows a three-dimensional framework assembled from VO5 square pyramids, PO4 tetra­hedra and Co[O2(H2O)4] octa­hedra. The CoII ions have local 4/m symmetry, with the equatorial water mol­ecules in the mirror plane, while the V and apical O atom of the vanadyl group are located on the fourfold rotation axis and the P atoms reside on \overline{4} sites. The PO4 tetra­hedra connect the VO5 polyhedra to form a planar P–V–O layer. The [Co(H2O)4]2+ cations link adjacent P–V–O layers via vanadyl O atoms to generate an unprecedented three-dimensional open framework. Powder diffraction measurements reveal that the framework collapses on removal of the water mol­ecules.