The design of salid sorbents and heterogeneous catalysts from nanoporous materials which have structures with large pare size represents one of the most sought quests in zeolite science. Traditionally , the search far these materials has focused on the use of large organic molecules as structure-directing agents (SDAs) ; however , the use of such large molecules is currently reaching a limit imposed by the chemical requirements , specially solubility and hydrothermal stability , that organic molecules have to fulfil to behave as efficient SDAs. In our group, we have recently proposed a synthetic alternative based on the application of supramolecular chemistry , which drives the aggregation of organic molecules in multimolecular species by the establishment of strong intermolecular interactions, to promete the formation of supramolecular entities of larger size potentially able to direct the crystallization of large-pore materials. 1 A simple way to realise this supramolecular self-assembly is by using organic molecules with aromatic rings as SDAs that tend to form aggregates stabilized through rr-rr interactions. Following this idea, (1 R, 25)-ephedrine (EPH) (Fig.1) and derivatives have been selected as SDAs far the present work , because of their capacity to form supramolecular aggregates. 2 The synthesis of microporous aluminophosphates has been carried out by hydrothermal methods in the presence of EPH as SDA. We have analysed a systematic variation of synthesis parameters in arder to understand the factors that control the supramolecular chemistry during structure direction of microporous frameworks by these molecules. The solids have been characterized by many techniques specially fluorescence spectroscopy. Fluorescence allows far the identification of the supramolecular state since when molecules are aggregated , the energy difference between the electronic levels decreases , and the emission band corresponding to aggregates is shifted to longer wavelengths with respect to the monomer emission (Fig. 1). Particularly , our group was the first to use this technique to know this type of aggregation because is very importan! far us to know which is the level of aggregation in arder to gel structures with large pare size. Results show that EPH tends to direct the crystallization of the AFI structure in the presence of dopants. In the case of the synthesis without dopants , low-dimensional phases are obtained. lnterestingly , our results show that aggregation depends strongly on the temperature (higher temperatures lead to higher aggregation) , the amount of dopants (lower dopan! contents involve a higher aggregation) and the organic canten! (a higher concentration of the organic molecules brings a higher aggregation) (Fig. 1).

Trabajo presentado en el 5th Early Stage Researchers Workshop in Nanoscience, celebrado en Madrid (España) del 17 al 18 de junio de 2019.

Peer Reviewed