Synthesis and Structural Characterization of Porous Metal Phosphonates
This presentation will focus on the challenge of developing porous metal arylphosphonates with both high crystallinity and functional porosity. Metal phosphonates are an extensive class of materials based upon extended inorganic-organic architectures such as chains, layers and three-dimensional networks. Metal phosphonates generally favor extended inorganic architectures leading to pillared materials with no porosity. We found that the use of template molecules, type of ligand and choice of metal ions could be used to deviate from the pillared structure. Two types of materials and their structure-property relationships will be presented.
For a zinc phosphonate, a layered structure was converted into a three-dimensional framework by using small template molecules in the solvothermal reaction. The compound exhibited reversible dehydration behavior. The change in the framework structure and guest positions was monitored during this process by in situ X-ray diffraction and solid state NMR.
Porous aluminum phosphonates were synthesized; however, the polycrystalline nature of the products can hinder the investigation of their structure-property relationships. These materials exhibited reversible dehydration behavior, which had a dramatic influence on permanent porosity of the material. The stability of the dehydrated phase was found to be the result of the geometry of the aluminum atom, which in some cases has coordinatively unsaturated metal sites.