Pore cage-like

There are two types of stmctures one provides an internal pore system comprising interconnected cage-like voids the second provides a system of uniform channels which, in some instances, are one-dimensional and in others intersect with similar channels to produce two- or three-dimensional channel systems. The preferred type has two- or three-dimensional channel systems to provide rapid intracrystalline diffusion in adsorption and catalytic apphcations. 

Pore diameter (dp) for channel-like PMSs according to the BJH pore size distribution, which, however, underestimates the effective pore diameter by circa 1.0 nm, as shown by theoretical and geometrical calculations [48, 49] pore diameter of cage-like PMSs according to Ravikovitch and Neimark [50],... 

These are sodium and calcium aluminosilicates which have cage-like crystal lattice structures containing pores of various sizes, depending on their constitution. They can absorb small molecules, such as water, which can fit into the pores. The most commonly used types 3A, 4A, and 5A have pore sizes of approximately 3A, 4A, and 5A respectively, and they are available in bead or powder form. After activation at 250-320°C for a minimum of 3h they are probably the most powerful desiccants available.iC ) They can... 

The combination of metal ions and appropriate ligands to form macrocyclic, cage-like, and extended network structures has become a powerful tool for the construction of systems having cavities, pores, or channels, and is currently one of the most important topics in chemical and material sciences. Applications are visualized for a wide range of fields, such as ion and molecular recognition, sorption, filtration,... 

J.R. Matos, M. Kruk, L.P. Mercuri, M. Jaroniec, L. Zhao, T. Kamiyama, O. Terasaki, T.J. Pinnavaia, and Y. Liu, Ordered Mesoporous Silica with Large Cage-like Pores Structural Identification and Pore Connectivity Design by Controlling the Synthesis Temperature and Time. J. Am. Chem. Soc., 2003, 125, 821-829. 

The intracrystalline channel cavity-pore-cage system in zeolites is surrounded by the lattice and therefore is submitted to the zeolite crystal field. This results in solvent-like and even electrolyte-type properties. One has seen above how cations could be easily exchangeable. It may also exist an interaction between any occluded ionic compound and the zeolitic framework. Salts, especially salts of univalent anions, have been shown to penetrate the zeolite structure and fill the available space even if the openings of the cavities (as the 0 -ring of 0.24 nm in size in sodal te cage of Y zeolite) is smaller than the size of the anion (CIO, NO for instance). The interesting feature is then the enhanced thermal stability of the occluded salt. 

Figure 9.20 Typical pore network topologies found in ordered mesoporous silica materials. From left to right 2-D hexagonal p6mm pore structure, bicontinuous 3-D cubic la 3 d) pore structure, 3-D interconnected body-centered cubic cage-bke structure Im 3 tri), and 3-D interconnected/ace-centererf cubic cage-like structure Fm 3 m).

In the family of copolymer-templated materials, ordered mesoporous silicas consisting of interconnected large cage-like pores are also of significant interest. 

As the calcination temperature increased from 550 to 800°C, a gradual decrease in the pore cage diameter from 7.7 to 6.8 nm was observed for the samples with fully accessible mesopores (see Figure 11.2). For the sample calcined at 900 C, the diameter of accessible mesopores was 6 nm, but most likely only a fraction of the mesopores were actually accessible, while the pore size distribution did not reflect the closed (inaccessible) mesopores, which cannot be probed using the gas adsorption method. Therefore, the pore cage diameters for the sample with a fraction of closed mesopores (calcined at 900 C) and the sample with closed mesopores (calcined at 950°C) were assessed through the extrapolation of pore diameter data for the materials with accessible mesopores. The extrapolation was based on an... 

Cage-like pore structure, such as a spherical pore with entranees... 

It was therefore, concluded that since the metallic potassium was mobile at the activation temperatures, it must be intercalated within the carbon matrix. As a result, several atomic layers of carbon were widened and formed cage-like pores. 

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