Hydrothermal synthesis metal-organic frameworks

Yaghi OM, Li H (1995) Hydrothermal synthesis of a metal-organic framework containing large rectangular channels. J Am Chem Soc 117 10401-10402... 

Porous materials are classified into several kinds depending on the pore size. According to the International Union of Pure and Applied Chemistry (lUPAC) notation, microporous materials have pore diameters of less than 2 mn and mesoporous materials have pore diameters between 2 and 50 nm. Macroporous materials have pore diameters of greater than 50 nm. Hydrothermal synthesis has been the technique of choice to prepare microporous phases. Ordered porous materials, including ordered mesoporous materials and the metal organic frameworks (MOFs), have also been synthesized generally under hydrothermal conditions [1-5]. In this section, we briefly present the synthesis of mesoporous silica materials and MOFs. 

Guo H-D, Guo X-M, Batten SR et al (2009) Hydrothermal synthesis, stmctmes, and luminescent properties of seven dlO metal-organic frameworks based on 9,9-dipropylfluOTene-2,7-dicarboxylic acid (H2DFDA). Cryst Growth Des 9 1394—1401... 

Metal-organic frameworks can be synthesized with a wide variety of metal cations and a large choice of functionalized organic linkers by use of various synthesis methods, such as solvothermal (hydrothermal), microwave heating, ultrasonic, mechanochemical, electrochemical synthesis, and the spray-drying. However, only the conventional solvothermal (hydrothermal) method is well studied for MOF synthesis. In a typical solvothermal synthesis, both organic and inorganic precursors are dissolved in solvent... 

Hybrid framework compounds, including both metal-organic coordination polymers and systems that contain extended inorganic connectivity (extended inorganic hybrids), have recently developed into an important new class of solid-state materials. We examine the diversity of this complex class of materials, propose a simple but systematic classification, and explore the chemical and geometrical factors that influence their formation. We also discuss the growing evidence that many hybrid frameworks tend to form under thermodynamic rather than kinetic control when the synthesis is carried out under hydrothermal conditions. Finally, we explore the potential applications of hybrid frameworks in areas such as gas separations and storage,... 

In contrast to these post-synthetic modifications, it is also possible to functionalize the pore walls directly during the synthesis, as was first shown by Mann and co-workers [7,8] and Stucky and coworkers [9], who used trialkoxysilanes R-Si(OR )3. In our approach, such R Si(OR )3 molecules substitute for part of the TEOS. After hydrolysis, they serve as additional framework components during the hydrothermally induced condensation. An essential condition for this approach is that the trialkoxysilane does not destroy the micellar arrangement of the surfactant, which gives rise to the mesostructure. In mesostructures produced in this way, the R residues should be covalently linked to the silica walls. After the synthesis, the organic surfactant molecules can be removed by extraction so that a modified mesoporous material should remain. For example, when using phenyltrimethoxysilane (PTMOS), phenyl groups may become attached to the walls of the mesopores these can be utilized for further modifications, e.g. the immobilization of metal complexes. 

The most efficient catalysts in liquid-phase oxidation of organic compoimds were crystalline mked oxides [1]. They are ionic mixed oxides or mixed oxides containing oxides supported on oxides. In the latter case, the catalytic activity of the oxide support is increased by adding one or more metal components or is obtained by immobilization of metal oxides on inactive oxide support. Metal ions were isomorphously substituted in framework positions of molecular sieves, for example, zeolites, silicalites, silica, aluminosilicate, aluminophosphates, silico-aluminophosphates, and so on, via hydrothermal synthesis or postsynthesis modification. Among these many mixed oxides with crystalline microporous or mesoporous structure, perovskites were also used as catalysts in liquid-phase oxidation. 

The literature on inorganic open-framework materials abounds in the synthesis and characterization of metal silicates, phosphates and carboxylates. Most of these materials have an organic amine as the template. In the last few years, it has been shown that anions such as sulfate, selenite and selenate can also be employed to obtain organically templated open-framework materials. This tutorial review provides an up-to-date survey of organically templated metal sulfates, selenites and selenates, prepared under hydrothermal conditions. The discussion includes one-, two-, and three-dimensional structures of these materials, many of which possess open architectures, The article should be useful to practitioners of inorganic and materials chemistry, besides students and teachers. The article serves to demonstrate how most oxy-anions can be used to build complex structures with metal-oxygen polyhedra. 

---