ABSTRACT
Natural and synthetic zeolites belong to the group of molecular sieves existing in more than 1000 reported materials that are three-dimensional microporous crystalline solids. All silica zeolites are three-dimensional microporous crystalline solids, which are built from SiO2 tetrahedra linked in the corners, sharing all oxygen atoms. The structure directing agents are often occluded in the microporous cavities and channels of the synthesized materials, contributing to the stability of the obtained zeolite. The mesoporous structure can be regulated by a complex choice of templates, surfactants, adding auxiliary organic chemicals, for example, mesitylene and changing reaction parameters, for example, temperature and compositions. The mesoporous hosts must be carefully dried before adding the organosilane precursors to elude their autocondensation in the presence of water. Postsynthesis methods, such as functionalization of pore walls can affect the pore size and the surface chemistry in mesoporous molecular sieves materials. Then zeolite-based membranes will be molecular sieves, and consequently it may be used for gas separation processes.
