Synthesis and Characterization of New Iron and Zinc Phosphate Materials with Open Framework
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Synthesis and Characterization of New Iron and Zinc Phosphate Materials with Open Framework Yanning Song, Natasha A. Chernova, Peter Y. Zavalij and M. Stanley Whittingham Department of Chemistry and Institute for Materials Research, State University of New York at Binghamton, Binghamton, NY 13902-6016 ABSTRACT Open framework materials are of great interest due to the applications in the fields of adsorption, ion exchange, molecular sieving and catalysis. Metal phosphates are very important open framework materials due to the rich crystallography. Several new iron phosphate materials have been synthesized and characterized in our lab. Two new iron (III) phosphates, FePO4, have been synthesized from careful dehydration of hydrothermally prepared monoclinic and orthorhombic hydrated phosphates FePO4·2H2O. Reversible insertion and extraction of lithium into new iron phosphate hydroxide materials with 3-d rod-packing framework shows it to be an excellent intercalation material. Several other transition metals are also incorporated successfully into these compounds without changing the structure. With ethylenediamine as template, 1-D chain, 2-D layered and 3-D network iron phosphate materials were synthesized. The structure, electrochemical and magnetic properties of these compounds were studied. Meanwhile, two new zinc phosphates with methylammonium templates were also synthesized. There are infinite ZnO-Zn chains in one of the compounds, while closed 4-member circuits made up from Zn-O-Zn linkage present in the other.
INTRODUCTION Open-framework phosphate materials have attracted a great deal of interest recently for their applications in heterogeneous catalysis, adsorption, separations and ion exchange processes [1, 2]. In nature, iron phosphate minerals have rich crystal chemistry and are viewed as one of the most perplexing minerals [3]. Previously, at least 3 different phases has been investigated, the normal α-quartz phase [4], the high-pressure orthorhombic phase [5], and the other orthorhombic phase from the lithium extraction of LiFePO4 [6]. Monoclinic and orthorhombic dihydrated iron phosphates FePO4·2H2O [7, 8] have also been studied from powder data. Recently they were redetermined from single-crystal data [9]. Without changing the framework, the hydrates can lose the hydrated water and turn to monoclinic and orthorhombic anhydrous iron phosphates. Using amines as templates, several iron phosphate materials with different dimensionalities were synthesized [10]. Zinc phosphates, having total charge (+2 and +5) similar to porous aluminosilicates (+3 and +4), are also well studied as open framework structures. Different inorganic and organic species were successfully incorporated into the structure [11]. Here we report our study on some open framework iron phosphates and zinc phosphates. They are monoclinic and orthorhombic hydrated and anhydrous iron phosphates, iron hydroxyl phosphates with “rod-packing” structure, ethylenediamine templated iron phosphates with different dimensionalities, and zinc ph
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