Strategy aimed at the controllable synthesis has been focused on the control of micro-, meso-, and macroscale, including synthetic methods, architecture concepts, and fundamental principles that govern the rational design and synthesis. In this review, synthesis mechanisms and the corresponding pathways are first demonstrated for the synthesis of mesoporous silicates from the surfactant-templating approach. Virtually all mesoporous silicates begin with an understanding of the interactions between organic surfactants and inorganic species, as well as among themselves. In combination with some other synthetic techniques, the EISA method, which was known before a method for preparing mesoporous silica thin films, are shown here as a facile method to fabricate highly ordered mesostructured materials. Synthesis factors are essential for a beginner to start their research work, including surfactant selection, hydrothermal method (pH value, synthesis temperature, and hydrothermal treatment), nonaqueous synthetic technique, separation, drying, postsynthesis (secondary synthesis and recrystallization), and removal of templates. We show here a step-by-step choice according to their principles and recent developments. High-quality mesoporous products will be easily obtained provided that these factors can be fully understood. The controllable synthesis on mesoscale mainly includes mesophases (interface curvatures and arrangement of symmetries), pore sizes, and connecting manners. Besides the general discussion on the mesophase tailoring, the control of the pore size and the pore connecting manner is also presented. Typical mesostructures are introduced by dividing them into 2D, 3D, disordered, and other mesostructures. Soft-templating approach is one of the most general strategies now available for creating nanostructures. The assembly of surfactants and silicate species is normally carried out in solutions or at the interface to allow the required driving force for the formation of nanostructures. Relying on sol-gel, solution, and surface chemistry, there is great potential to explore novel strategies for mesostructures, especially a strategy that can utilize interfacial tension. Items that attract attention also include the control of weak interactions such as the hydrophobic interaction between the assembling components. In view of the fact that surfactant self-assembly can occur with components larger than molecules, the assembly of nanoparticles larger than 1 nm continues to be a challenge and an interest in condensed matter science. The creation of novel mesoporous silica mesostructures is in its fantasy, including mesophases, pores, etc. Novel synthesis strategies that are simple and mild, as well as new surfactants will be much in demand in the future. For example, low-temperature solid-state reaction methods and chemical vapor deposition (CVD) on interfaces could be used for the preparation of ordered mesoporous materials. Amphoteric surfactants, multihead quaternary ammonium ions, chiral surfactants, anionic surfactants, block copolymers (diblock copolymers A-B and triblock copolymers A-B-C) and noncovalently bonded A + B type polymers are very useful for the synthesis. Amphoteric surfactants, multihead quaternary ammonium ions, and anionic surfactants are used to control the surface charge matching with silicate oligomers. The adjustment of the surface charges in silicate species also strongly influences Coulombic interactions. Both the charges on the silicate and those on the surfactants offer possibilities for new mesostructures and pore topologies. The mesostructures templated by amphiphilic block copolymers are limited compared with their rich lyotropic mesophases. For example, until now 3D cubic silicate mesostructures with space groups of Pm3n, Pn3m, Fd3m, and Pm3m have not been obtained by using block copolymers as templates. ABC triblock copolymers possess much richer ordered microdomains and more diverse components compared with ABA triblock copolymers. The hydrophobic/hydrophilic properties of ABC copolymers strongly depend upon the interaction factors (χAB, χAC, χBC) and the component factors (xc4A, xc4B). Therefore, dream mesostructures such as Q214 (I4132), Q230 (Ia32), O70 (Fddd), and sponge-like L3 lamellar structures can be formed that have so far not been realized in mesoporous silicates. Significant work in block copolymers is expected for the manufacturability of diverse mesostructures. Recent progress on the large-pore mesoporous silicates templated by high-molecular-weight block copolymers (e.g., PS-b-PEO) has led to important advances in the synthesis. We believe that future efforts will be focused on seeking suitable block copolymers to directly synthesize highly ordered mesoporous silicates with pore sizes even larger than 50 nm. Moreover, bimodal and hierarchical pores and chiral pore channels are also on the way. To meet the practical applications, more complex mesoscopic structures, vesicles, single crystals, or large crystals (>20 μm) for structural solutions, etc. are desired. In addition, the functionality of organic modification either in surface or in pore wall matrixes by using siloxane or nanocrystals is worthy to be exploited. 350-355 The mesostructure with crystalline pore walls has long been a hot topic. On the consideration that crystallization always accompanies the collapse of mesostructures, the interactions between SDAs and inorganic silicate species or the roles of SDAs get more prominence. If the crystallization can occur at a condition that SDAs are stable inside the mesopores, confined crystallization on inorganic pore walls may come into being. On the other hand, the use of ionic block copolymers with amine headgroups is expected. The block copolymer backbones and the amine headgroups may be used to induce the formation of mesostructures and crystalline (microporous) frameworks, respectively. These advances must be made in conjunction with analytic and resolved studies that will further elucidate the true space on mesoscale. The full-scale characterization of mesostructures, pore sizes, pore connection manners, and morphologies will guide the practical applications in protein separation, catalysis, environment protection, and photonic crystals. © 2007 American Chemical Society.
