Pyknosil-to-Zeolite Hydrothermal Conversion of Magadiite into Mordenite

[EN] Layered silicates can be versatile precursors for the preparation of porous materials. Their transformation into zeolites typically employs organic structure-directing agents and seed-assisted crystallization, as in interzeolite conversions. Several zeolite topologies have been synthesized using magadiite; however, the role of magadiite in these processes remains unclear. The recent resolution of the magadiite structure provides an opportunity to integrate and reinterpret existing knowledge on this topic. Here, we report an unusual conversion of the layered hydrous silicate magadiite into mordenite triggered solely by the external addition of aluminum to a precrystallized magadiite gel. Aluminum disperses in the solid, occupying distinct framework sites, while a reorganization of ring-building units occurs, resulting in a marked decrease in the amount of surface silanol/silanolate groups. This restructuring proceeds without evidence of amorphization, accompanied by a progressive increase in surface area and growth of morphologically prismatic mordenite particles in contact with the magadiite plate-like particles. This transformation of a dense pyknosil-like structure into an open zeolite framework exhibits features of solid-phase reorganization triggered by aluminum supplied from the solution. These findings introduce a seed- and OSDA-free route for converting layered silicates into zeolites, expanding the conceptual and synthetic space for tailored microporous materials.