Extra-large micropore

From 12-Membered-ring Micropores to Extra-large Micropores... 

On the basis of these structural features, it is easy to understand why zeolites constructed by Si and A1 cannot have extra-large pores. Nevertheless, pure-silica zeolites with 14-membered rings, i.e. CIT-5 and UTD-1, have been synthesized recently, and further investigation into crystallization mechanisms in combination with the vast experimental data available and with theoretical simulation and computation may help us to rationally design and synthesize extra-large microporous aluminosilicate molecular sieves with special channels such as multidimensionally interconnected and chiral ones. 

The discovery of extra-large microporous materials facilitates research on the catalytic reaction of large and medium molecules, and also promotes host-guest chemistry and related advanced materials. 

As mentioned earlier in this chapter, it is the social demands and wide applications of porous materials that keep them under continuous exploration. From natural zeolites to synthesized ones, from low-silica zeolites to high-silica ones, from aluminosilicate molecular sieves to aluminophosphate-based ones, from extra-large microporous materials to mesoporous materials, and from inorganic porous frameworks to MOFs, together with newly emerging macroporous materials, all these porous materials have ordered and uniform porous systems. 

In addition, in the field of dewaxing (gas oils, HDC residues, lubricating oil, etc.), synthesis of novel molecular sieves with better adsorption and separation abilities is highly desired. In the past 20 years, thanks to the discovery of many molecular sieves with new compositions and structural features [secondary building units (SBUs) and pores], there have appeared a number of new application fields for molecular sieves, such as basic catalysis, extra-large microporous molecular sieve catalysis, redox catalysis, asymmetric catalysis, and dual- and multi-functional catalysis.1-201 All of these will lay a further solid foundation for the development of molecular sieves in catalysis, adsorption, and separation. 

DACH, and H20 with molar proportions I.OP2O5 l.OZnO 2.5 DACH 117H20 at 180 210°C for 2d. Like other extra-large microporous phosphates described above, the thermal stability of ND-1 is poor. Upon heating to 350 °C, its structure collapses with the loss of organic amines, and converts into Zn2P207 above 700 °C. 

Like known metal phosphates with extra-large microporous channel structures, the structure of ZnHPO-CJ 1 is unstable upon heating due to the existence of P H groups and strong H-bonding guest-host interactions. When heated at 280 °C for 3h, its structure collapses after the removel of the occluded organic molecules. 

From the above descriptions of many extra-large microporous phosphates, the syntheses and structural features of such phosphates can be further understood and some common rules can be started as follows ... 

As opposed to the extra-large microporous high-silica compounds UTD-1 and CIT-5, which are templated by bulky organic cations with low charge density, many metal... 

Table 5.18 Extra-large microporous compounds and their corresponding SDAs...

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