Solvothermal synthesis, characterization and mode of formation of aluminophosphate chains, layers and frameworks.

摘要

The solvothermal synthesis of aluminophosphates is described, using organic amine additives ranging from primary to quaternary to cyclic. A tetraethylene glycol solvent led to a series of novel aluminophosphate crystal structures, denoted UT-n, where UT denotes University of Toronto and n denotes structure type. Of the eight structures that were discovered to date, two are one-dimensionally extended chains, five are two-dimensional layers and one is a three-dimensional framework. For all, the inorganic architecture is anionic and is charge-balanced by occluded alkylammonium template molecules. The chain and layered structures each contain an extensive hydrogen bonding network between the terminal oxygens of the phosphate groups and the ammonium hydrogens. A series of alkylammonium phosphate structures were also discovered, which contain layers of phosphate molecules separated by interdigitated or bilayers of alkylammoniums.; The aluminophosphate and phosphate solids were characterized by a variety of techniques, including VT-PXRD, TGA, MS, SEM and solid state NMR. Many interesting results were found, such as a topotactic anionic framework to neutral framework transformation. The data also showed an unprecedented aluminophosphate chain to layer solid state transformation, where both end products were previously synthesized and fully solved UT-n crystal structures.; This is followed by a new model for the mode of formation of aluminophosphates, which points out previously unrecognized structural aspects and is based on experimental evidence. The model involves a crystallizable chain precursor, which on hydrolysis, rearrangement and condensation, leads to a theoretically infinite number of possible chain types. These chains connect together and thereby account for the architectures, dimensionality and observed structural trends of potentially all known and theoretical aluminophosphate chains, layers and frameworks. Examples of each will be given.; Finally, changing the template molecule to an amphiphilic n-alkylamine (C{dollar}sb{lcub}rm n{rcub}{dollar}H{dollar}sb{lcub}rm 2n+1{rcub}{dollar}NH{dollar}sb2{dollar}) resulted in a series of novel mesolamellar aluminophosphates (MLA's). The phase(s), crystallinity and morphology of the resultant product were found to be highly dependent on carbon chain length. For n = 8 to 12, a series of remarkable surface morphologies were discovered. After the characterization of the MLA materials, a preliminary mode of formation will be described, involving an alkylammonium phosphate liquid crystal phase.