**2. Porous systems**

**1. Introduction**

44 Advances in Petrochemicals

production of greenhouse gas emissions [3].

Prussian blue analogue materials.

compared with the 2D systems.

in zeolites for the new materials obtained [5].

them [1, 2].

In recent years, micro-porous and nanocomposites have been wide, and there are special interests in specific areas in order to generate improved technological processes such as separation, gas adsorption, ion exchange, and heterogeneous catalysis, to mention some of

Particularly in the separation and gas adsorption area in microporous and nanosystems, research has focused on hydrogen's adsorption and storage as an alternative energetic alternative resource since this element might become a long-term fossil fuel substitute because its caloric power is three times higher than gasoline (142 kJ/mol). It is noteworthy that when the hydrogen is at room temperature in its supercritical state (Tc = 32.7 ° K), storage is difficult, hence the importance of finding new porous materials having cavities with the ability to store it safely. Similarly, once stored, it can be used in mobile systems (automotive), avoiding the

Studies on porous media properties have focused mainly on inorganic materials such as zeolites or carbon-based materials such as activated carbons, the last one having a high porosity

In order to generate a material having defined pores and specific physicochemical properties, the interest is held in the synthesis of new porous materials showing specific conditions from defined synthesis models, examples of these are as follows: (i) layered systems (2D), tetracya‐ no-niquelates attached to a metal transition [M (H2O)2 (Ni (CN)4) n (H2O)], M = Co, Ni, Mn, known as Hoffmann-type compounds; and (ii) latticed porous materials, hexacyano-cobaltates bound to a transition metal [M3 [Co (CN)6] 2 nH2O], M = Co, Ni, Mn, Cd, Cu, Zn, known as

The importance of lamellar materials known as two-dimensional (2D) lies in the ability to include molecules in their interlamellar spaces known as guest molecules, with the sole purpose of generating pores or cavities with specific characteristics according to the same properties of the included molecule, generating a three-dimensional network, in addition, to be able to store various molecules such as H2 and CO2 in the pores obtained. The transformation of a layered structure in a porous structure throughout a molecular spacer insertion was first introduced into the clay mineral smectite to overcome the limitations of the size of the cavities

The proposed 2D systems have water molecules between the sheets, joined by the system for various attractive forces. There are two types of water molecules included in the material, some are called coordinated water molecules, which are forming bonds with transition metals present in the sheets and play the role of guest molecules to form the pillars of the final structure. Additionally, there are others known as zeolitic water, which are placed in the

The water molecules (coordinated and zeolite) are also in the hexacyano-cobaltates, but the interaction with the system is weaker so the energy required to abandon the system is lower

cavities or interlamellar region linked by hydrogen bond type interactions.

on one side and an irregular pore, while zeolites have opposite characteristics [4].

At the end of the 1990s, there were basically two types of porous materials: inorganic and carbon derivatives. In the case of the former, the two most important subclasses of materials with open structures are aluminosilicates (zeolites) and aluminophosphates (AlPO4s); whose crystalline lattices offer permanent porosity to be stable before the removal of molecules of water of hydration. The market of zeolites is of several million tons per year, and it has success in a wide range of applications, especially in the petrochemical industry and the hydrocarbon separation, purification of gases and liquids, and the catalytic fragmentation of chain hydro‐ carbons long. Additionally, they have also been applied in ionexchange as detergent additives and the separation of gases and solvents, for example, as "molecular sieves" to the dehydration of organic solvents.

In the case of activated carbons, they have large specific surface area as well as high porosity; however, they have a disordered structure. These materials are widely used in the processes of separation, catalytic converters, capacitors, storage of gas, and biomedical engineering applications [11].
