The synthesis, characterization, and proposed formation mechanism of tin(II) and antimony(III) phosphates and related materials
Crystalline nanoporous materials like zeolites and metal phosphates (e.g. AlPOs) are used commercially for catalysis, adsorption, molecular sieving, and ion exchange. Their properties are related to both their porous architectures and chemical compositions. Materials that incorporate tin(II) and antimony(III), with stereochemically active lone electron pairs, could impart properties different from those of materials based on aluminum, cobalt, zinc, iron, and other metals that adopt [MO4] tetrahedra. Exploratory hydrothermal synthesis resulted in thirty new tin(II) and antimony(III) materials, including the first open-framework antimony(III) phosphate. Structure determination was by single crystal X-ray diffraction. Some materials incorporate a three-ring chain motif observed in other metal phosphates. Previously proposed metal phosphate formation mechanisms are shown not to adequately describe its formation. A new mechanism is proposed, adapting the Partial Charge Model of Livage, et al. to tin(II) and antimony(III) phosphates. This mechanism, starting from open chain metal phosphate `wires' (with M-O-P bonds), is then extended to other metal phosphates.