Synthesis and ab-initio structure determination of organically templated magnesium phosphates from powder diffraction data

Abstract

NH4MgPO4·H2O (dittmarite), 0.5·[NH3(CH2)2NH3]2+[MgPO4·H2O]− (UiO-24-EN) and 0.5·[NH3(CH2)4NH3]2+[MgPO4·H2O]−·H2O (UiO-24-DAB) were prepared by hydrothermal methods, and their structures were determined ab-initio from powder diffraction data. The three compounds are composed of inorganic magnesium phosphate layers separated by charge compensating ammonium or organic cations and water molecules. Corner sharing magnesium octahedra crosslinked by phosphate tetrahedra form the inorganic layers in dittmarite. This atomic arrangement is identical in the UiO-24 type of compounds, and these structures can be viewed as dittmarite being intercalated by diamines and water molecules. The compounds have been characterized by thermogravimetric analysis, solid-state 31P MAS NMR spectroscopy and ion exchange experiments.