Zeolite‐Containing Materials with Hierarchical Porous Structures

Abstract

Recent advances in synthesis and characterization of hierarchical zeolitic structures by direct and post-synthetic treatment methods and structured devices by in situ and ex situ zeolite coatings on open-cellular ceramic foams as non-reactive and reactive supports will be highlighted. Zeolite-containing materials were synthesized, generally employing two different approaches, i.e., template-directed and post-synthetic methods. Differently, the coating approach yields hierarchical porous composites by deposition or in situ synthesis of microor mesoporous frameworks onto porous carriers. Such a surface modification (functionalization) of structured (monolithic) support surfaces with an additional porous material of a different pore size regime results in a hierarchically organized system. In this regard, the use of appropriate materials like microporous zeolites permits the development of a hierarchical organization of the porosity on two or three different porosity levels. Thus, hierarchically organized structured zeolitic composites can benefit in their applications from both, the zeolitic function and the function of the support. Recent trends and advances in the field of hierarchical zeolites are reviewed with special emphasis on the characteristics of structured materials, e.g., opencellular ceramic foams used as non-reactive as well as reactive supports. It is very important to identify the role played by the methods and/or supports with respect to the characteristics of the final hierarchical structures.