Microporous compounds

For microporous compounds with special compositions, calcination effects are even more severe. As compared with zeolites, these compounds have lower thermal stability. Strictly speaking, most of them are nonporous since removal of the occluded guest molecules by calcination usually results in collapse. This is due to strong H-bonds with the framework, coordination bonds, and sometimes the templating molecule is shared with the inorganic polyhedra. Relevant examples of low-stability microporous compounds with interesting structural features are zeolitic open-framework phosphates made of Ga [178], In [179], Zn [180], Fe [181],... 

Solvent extraction is the most important technique for recovering surfactants from mesoporous materials. However, it is not very effective when applied to microporous compounds. Davis et al. [186] successfully extracted borosilicate and silicate BEA stractures with acetic acid while a small template fraction could be removed for the aluminosilicate. 

Recent reports describe more sophisticated detemplation methods. However, they are limited to mesoporous materials for the reasons described before. We show how Fenton chemistry can fulfill various missing challenges (i) it provides a powerful oxidation capacity at low(er) temperatures and (ii) it can work for microporous compounds as well. 

Davis, M. E. Lobo, R. F. Zeolite and Molecular sieve synthesis. Chem. Mater. 1992, 4, 756, Feey, G, The new microporous compounds and their design. C, R. Acad. Ser. Paris Ser, I11998, 1. 

The fluoride route of synthesis seems very rich and already provided four among the six most open frameworks described up to now in the litterature in the category of microporous compounds (0 < A) VSB-1 [22] cloverite [11], ULM-5 [23] and ULM-16 [24] with tunnels limited by 24, 20,16 and 16 polyhedra respectively. These four solids are really porous, the porosity being generated by the elimination of the template either by thermal or chemical methods which preserve the inorganic framework. 

T. Loiseau and G. Ferey, Oxyfluorinated Microporous Compounds, VII. Synthesis and Crystal Structure of ULM-5, a New Fluorinated Gallophosphate Ga1g(P04)14 (HP04)2 (OH)2F7 [ I I3N(CI I2)6NI I3 4 6I I20 with 16-Membered Rings and both Bonding and Encapsulated F. J. Solid State Chem., 1994, 111, 403 415. 

Synthetic Chemistry of Microporous Compounds (I)-Fundamentals and Synthetic Routes... 

Figure 3.1 Commonly used autoclaves in the laboratory for the synthesis of microporous compounds...

Synthetic Approaches and Basic Synthetic Laws for Microporous Compounds... 

The crystallization of microporous compounds under microwave irradiation was developed in the 1970s, and was characterized by mild conditions, low energy consumption, rapid reaction, small particles, and uniform particle-size distribution. For example, under microwave irradiation and normal pressure, zeolite NaA could crystallize with a high crystallinity in a short time, even less than 1 minute. Thus, this new synthesis approach can quickly and continuously produce molecular sieves with low energy consumption. The microwave synthesis of zeolite NaA and microporous AIPO4-5 and the ion exchange reaction of zeolite Ce-/i will be discussed in detail later in this section. The successful synthesis of microporous FeAPC>4-5, CoAPO-5, CoAPO-44, VPI-5/771 zeolites Na-X, Na-Y, ZSM-5, and TS-1,[78] the preparation of molecular sieve membranes/791 the dispersion of salts or oxides into the channels of molecular sieves, and the modification or functionalization of the channel or structure of the molecular sieves under microwave irradiation have been reported as well/801... 

Numerous microporous crystallines with various structure types have been successfully synthesized by using microwave irradiation in the last decade. Compared with conventional hydrothermal synthesis, microwave synthesis has many advantages, such as narrow particle-size distribution, controllable morphology, broader parent mixture composition, and short crystallization time. It can be expected that microwave synthesis will play an important role in the rapid, energy-saving, and continuous production of microporous compounds. 

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