Hydrothermal synthesis, structures and catalytic properties of the new open-framework cobalt tungsten phosphates (enH2)3[Co3W4P4O28] and K6[Co3W4P4O28]·4H2O

Abstract

Two new 3D open-framework cobalt tungsten phosphates, (enH₂)₃[Co₃W₄P₄O₂₈] and K₆[Co₃W₄P₄O₂₈]·4H₂O, have been hydrothermally synthesised and characterized by single-crystal X-ray diffraction, thermogravimetry, elemental analysis and IR spectroscopy. Their anionic frameworks, built up from corner sharing CoO₄ and PO₄ tetrahedra, and CoO₆ and WO₆ octahedra, delimit 3D channels that consist of 7- and 8-rings. The channels in both compounds are occupied by the charge-balancing [enH₂]²⁺ or K⁺. In situ powder XRD study showed that the framework of (enH₂)₃[Co₃W₄P₄O₂₈] was stable up to 500 °C at which temperature the organic templates had been removed.