ICP-2: A New Hybrid Organo-Inorganic Ferrierite Precursor with Expanded Layers Stabilized by pi-pi Stacking Interactions

摘要

In this work we present the synthesis, characterization, and molecular modeling of ICP-2, a new layered ferrierite precursor with expanded layers. ICP-2 is obtained in fluoride medium from aluminosilicate gels with low H2O content, using the chiral cation (1R,2S)-dimethylephedrinium (DMEP) as the organic structure directing agent; ICP-2 can also be obtained as the Al-free form. The combination of physicochemical characterization of the material with molecular modeling indicates that ICP-2 is a layered material composed of ferrierite layers, where the organic cations play a dual structural role through the formation of supramolecular aggregates. On one hand, the organic cations stabilize the formation of the ferrierite layers with a core-shell structure, directing the formation of both the pseudo-10R channels (by supramolecular dimers aligned with the channel direction) and of the pseudocavities, with the trimethylammonium groups of DMEP fitting within. On the other hand, the aromatic rings of these organic cations in the pseudocavities develop pi-pi stacking. interactions with equivalent cations in adjacent layers, holding together the ferrierite layers expanded at a distance of similar to 20 angstrom, hence preventing the formation of H-bonds between the inorganic layers. The diastereoisomer (1S,2S)-dimethylpseudoephedrinium instead cannot direct the formation of ICP-2, which is explained because of its distinct conformational space which fits worse in the core-shell structure of ICP-2.