Nano‐Microporous Materials: Hydrothermal Synthesis of Zeolites

AbstractThis review focuses on the synthesis, crystallization mechanism, and crystal engineering of silica‐based zeolites. The introduction section provides a brief historical overview of zeolite synthesis and points out the main families of microporous solids. The main body of the article comprises two interrelated parts. The first presents basic information related to the zeolite crystallization, namely, (i) the key constituents of a zeolite‐yielding system; (ii) the reactions upon the action of mineralizing agent (OH−and F−); and (iii) the fundamentals of zeolite crystallogenesis. Emphasis is laid on the nucleation process, which is still not well understood. New insights into the zeolite nucleation gained by using colloidal and dense gel systems are discussed. The second part of the survey deals with in situ zeolite crystal engineering. Initially, the synthesis of nanosized particles is considered and then methods for the growth of large, at least 50 µm, zeolite crystals are presented. Further, the control of the crystal morphology via fine tuning of the synthesis variables is discussed. Hybrid zeolites obtained by grafting of organic functionalities during the crystallization reaction are also reviewed. Finally, methods for the synthesis of zeolites with hierarchical porosity are illustrated. This part is subdivided into two sections presenting polycrystalline hierarchical porous structures and single mesopore–containing zeolite crystals.