A Review on the Effects of Organic Structure-Directing Agents on the Hydrothermal Synthesis and Physicochemical Properties of Zeolites

The study on the synthesis of zeolites, including both the development of novel techniques of synthesis and the discovery of new zeolitic frameworks, has a background of several decades. In this context, the application of organic structure-directing agents (SDAs) is one of the key factors having an important role in the formation of porous zeolitic networks as well as the crystallization process of zeolites. There are various elements that are needed to be explored for elucidating the effects of organic SDAs on the final physicochemical properties of zeolites. Although SDAs were firstly used as pore generators in the synthesis of high-silica zeolites, further studies proved their multiple roles during the synthesis of zeolites, such as their influences on the crystallization evolution of zeolite, the size of the crystal and the chemical composition, which is beyond their porogen properties. The aim of this mini review is to present and briefly summarize these features as well as the advances in the synthesis of new SDAs during the last decades.