Un-assemblable layered aluminophosphates from self-assembling structure-directing agents: Effect of fluorine

Abstract

A new strategy for the synthesis of three new un-assemblable metastable AlPO-based layered framework materials is reported. By using organic molecules with aromatic rings that tend to self-assemble in water solution by establishing π–π type interactions, three new AlPO layered frameworks have been produced with benzylpyrrolidine and its meta- and para-fluorinated derivatives. These new layered materials occlude an extremely large amount of organic material. Interestingly, UV–Visible fluorescence results show that the molecules occluded within the frameworks form supramolecular aggregates, and consequently the crystallization of these structures is strongly dependent on the self-assembly ability of the organic molecules in water. As a consequence, the ortho-fluorinated derivative, which shows the lowest trend to aggregate in water, is not able to produce a stable self-assembled AlPO framework.

The self-assembly of the organic molecules within the frameworks driven by relatively weak π–π type interactions between the aromatic rings combined with a poor H–bond interaction of the heterocyclic tertiary N with terminal PO groups enable a simple un-assembly (delamination) process of the structures by treating the samples in water.