Organic-free one-step synthesis of macro/microporous LTA zeolite and its encapsulation of metal nanoparticles

Micrometer-sized hierarchical LTA-type zeolite crystals with uniform embedded macropores were synthesized via steam-assisted conversion (SAC) of spherical mesoporous silica particles (MSPs) impregnated with alkaline aluminate. The one-pot synthesis was achieved by direct transformation without the need of organic structure directing agents or pre-formed seeds. The obtained cubic hierarchical NaA zeolite materials were 2–5 μm in size which possessed a core-shell structure with a microporous wall in the shell and multi-hollow macropores about 400 nm in the core. Time-series studies revealed the in situ dissolution–crystallization formation mechanism, in which the mesoporous silica particles functioned as silica source as well as “space-filling” template. When the starting MSPs were pre-loaded with metal precursors, multi-hollow zeolite nanoreactor crystals with encapsulated metals were successfully synthesized by this strategy. The present study provides an organic-free way to fabricate hierarchical aluminosilicate zeolites with embedded macropore system.