Synthesis of a Ferrolite: A Zeolitic All-Iron Framework

Crystals of the first sodalite-type zeolite containing an all-iron framework, a ferrolite, Ba₈ (Fe₁₂ O₂₄ )Na_y (OH)₆ ⋅x H₂ O, were synthesized using the hydroflux method in nearly quantitative yield. Ba₈ (Fe₁₂ O₂₄ )Na_y (OH)₆ ⋅x H₂ O crystallizes in the cubic space group Pm3‾m with a=10.0476(1) Å. Slightly distorted FeO₄ tetrahedra are linked to form Fe₄ O₄ and Fe₆ O₆ rings, which in turn yield channels and internal cavities that are characteristic of the sodalite structure. Barium, sodium, and hydroxide ions and water molecules are found in the channels and provide charge balance. Magnetic measurements indicate that the ferrolite exhibits magnetic order up to at least 700 K, with the field-cooled and zero-field-cooled curves diverging. Analysis of the ⁵⁷ Fe Mössbauer spectra revealed two spectral components that have equal spectral areas, indicating the presence of two subsets of iron centers in the structure. Dehydrated versions of the ferrolite were also prepared by heating the sample.