*2.3.1. Host molecules (pillarization)*

The basic function of the pillarization is to include molecules in the interlamellar region to obtain a three-dimensional porous system with well-defined and specific characteristics according to the material or molecules that are embedded as a result. The interaction host species with active sites, which are normally present on the surface of the plates, is the driving force of the mechanism of formation of pillars in a structure laminating. These sites may be crystallographic positions or groups influenced by positive or negative charges, or sites with acid, basic, or polar character in general. The density of active sites on the surface on one side of the blade is expressed by the number of sites per cm2 of surface layer.

The reciprocal value of the density of surface represents the average area per active site. This value, also called free area, is an important characteristic of a laminated solid. Knowing this, it is possible in many cases to predict whether the full collation of guest molecule stoichiometry is viable or not. In nature, the surface density and availability of the active sites is usually the same on both sides of the layers. However, in some cases, there are asymmetric blades.

The layout of the active sites in each side of the blade and its free area can be determined precisely when the blade structure is known.

In general, the pillarization process variables are as follows [23]:


interlamellar surface is accessible only to water and other small polar molecules that are

The elimination of molecules of solvation by degassing at elevated temperatures results in a collapse of the interlamellar region, especially if interspersed compensating charge ions are small in relation to the occupied space; on the other hand, if the compensating charge ions are relatively large, they can have the role of pillars and prevent the collapse of the interlamellar regions when the middle of solvation is eliminated, resulting in solids called solid lamellar

**Figure 2.** Representation of a layered solid pillared, wherein pores are defined by the height of the interlamellar space (d2) and the lateral spacing (d1) between the guest molecules or pillars (P). R denotes the interlamellar region.

Laminar solid pillars can be described as sandwich compounds serving three important

**1.** Interlamellar species must be sufficiently robust to promote the vertical expansion of the blades (d2) and to prevent their collapse during any thermal process to which they are

**2.** The pillars must be sufficiently separated (d1) to allow access to molecules. Simply expanding the blades to molecular size, collation of pillars, is not significant in relation to the properties of adsorption and catalytic behaviour of solid if the interlamellar region is

**3.** The blades must be rigid enough to maintain the separation desired between pillars. Otherwise, the flexibility of the blades could close gaps between pillar and pillar.

an object of study important above all in the area of nanoscience and nanotechnology because they have been shown to generate opportunities in different fields of application, such as biomedical electronics, applications in the area of storage and energy conversion, and catalysis

The basic function of the pillarization is to include molecules in the interlamellar region to obtain a three-dimensional porous system with well-defined and specific characteristics according to the material or molecules that are embedded as a result. The interaction host

/g) makes these materials

Lamellar surface area presented by solids (between 100 and 1000 m2

pillars. Figure 2 presents a system that shows some characteristics of layered solids.

capable of solvated ions of compensation.

48 Advances in Petrochemicals

criteria:

[22].

subjected.

fully occupied by pillars.

*2.3.1. Host molecules (pillarization)*

**4.** Subsequent treatments such as drying, cleaning, etc.

The most important parameters affecting the formation and the properties of the polynuclear cations as agent formed with pillars are as follows [24]:


The water molecules in some materials tend to be regarded as pillars of the same due to interactions that generate with the transition metals present, and the study of these molecules provides information of the nature of the material.

Pillar materials include clay Al-montmorillonite and the Al-bentonite, which is used in gas-oil cracking and reactions of phenols hydroxylation reactions, respectively.
