Hollow Zeolite Capsules:  A Novel Approach for Fabrication and Guest Encapsulation

Abstract

Hollow capsules have recently attracted much attention because their unusual properties may find wide potential applications in chemistry, biotechnology, and materials science.

Synthesis of hierarchical porous materials with ZSM-5 structures via template-free sol–gel method

“…Other than steaming and acid-leaching dealumination method which often generates mesopores or macropores with wide size distribution, several strategies for the synthesis of hierarchical porous materials with ZSM-5 structures have been described in the literatures. Generally, soft [6] or rigid [7] templates are necessary for the formation of mesopores and macropores with narrow size distribution within those reported materials. Those methods can be also described as assembly of zeolite structures in the present of templates.…”

Advances in Microporous and Mesoporous Solids—Highlights of Recent Progress

“…[78,80±82] Tang and co-workers employed reactive shape transformations to form hollow zeolite capsules and three-dimensionally ordered macroporous zeolite monoliths. [76,77] In both cases, mesoporous silica spheres were coated with polyelectrolyte films to allow attachment of nanocrystalline silicalite-1 seeds. For the preparation of hollow zeolite capsules, the seeded spheres were exposed to vapor-phase transport (VPT) treatment with amines which led to formation of a zeolite crust around a hollow core.…”

Conversion of Fly Ash Cenosphere to Hollow Microspheres with Zeolite/Mullite Composite Shells

“…The negatively charged zeolite seeds were then deposited onto the FAC through soaking the positively charged FAC in the zeolite seeds suspension at a solution/FAC mass ratio of 5 [7]. The seeded FAC was finally rinsed in a dilute ammonia solution to remove excess zeolite crystals and dried at 100 C.…”

“…[7,9,10] These products are generally fabricated by the combination of the layer-by-layer (LBL) selfassembly technique and the sacrificial core±shell technique. [9] Additionally, Valtchev [10] obtained mechanically stable hollow zeolite spheres through a further secondary hydrothermal treatment before the removal of the template cores.…”

“…In this method, the hollow structure could spontaneously be formed simultaneously with the consumption of the nanozeolite pre-seeded mesoporous silica cores during the chemical treatment. [7] Fly ash (FA) is an aluminosilicate-rich waste produced in coal power plants and causes serious environmental problems. Great efforts have been made on the utilization of this waste.…”