1. diameter between 1 and 100 nm. These

1.

      Introduction The quantum leaps in the research area of nanotechnology have crucial impacts on our modern life and our lifestyle especially, that work to produce new tiny devices. For example, portable devices such as cellular phones and portable computers have irrevocably changed our lifestyle because they facilitate the communication whenever and wherever possible. As a result, such these researches may contribute to decrease energy consumption and waste production.Nanoporous materials is broadly accepted as one of the important branches of nanostructured materials science. These materials possess high specific surface area, large pore volume, uniform pore size and rich surface chemistry. The nanoporous materials present great potential and chances for generation of innovative functional materials with enhanced properties for applications in several fields including adsorption, selection, sensing, removal, storage, catalysis, and separation so they can be used in many applications such as chemical, environmental/energy, optics, electronics, medical, and biotechnological applications.As the Chinese proverb says “With clay, we make a jar.

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But it is the empty space inside that we need.”This summarizes the purposes concerning the science in regard to the porous systems: producing mateials which have empty cavities to utilize these cavities. In the past, porous materials had been acknowledged and they had been utilized in many applications such as filtration and liquid adsorption. For long time, dense efforts have been done to improve control of pore size, limit the pores diameter and well-organized shape to enhance its properties. Therefore, nanoporous materials have been obtained their name from the diameter of pores.

The purpose to produce these materials is to improve their properties and to take advantage from them in many applications such as ion exchange, separation, catalysis, sensor, biological, molecular isolation and purification. A nanostructured porous material is a system which has a regular pattern of pores with a diameter between 1 and 100 nm. These materials present diverse geometries, structures and chemical compositions and used as adsorbent systems, filtering membranes, supports for catalytic dispersion or incorporated in nano-reactors structures for controlled chemical reactions in confined space. 1.

2  Pores and porosityThere are two types of pores: closed and open pores. Closed pores are vacant cavities totally immersed in bulk materials, and these types of materials are fruitful in thermal and sonic insulation, or as lightweight materials for structural applications. However, open pores are associated with material surface and are used for separation, catalysis and sensing application.In open pores, surface roughness and pores should be distinguished. Therefore, pores are deep than size but surface roughness the size is larger than deep and more spread. The difference between porous systems depend on porosity parameters: such as the ratio between the pores volume and the total material volume.

Generally, porous materials have porosity between 0.2 and 0.95. 1.3 Classification of nanoporous materialsThere are fundamentally four main classification systems of nanoporous material:1.

      pore dimensions One of the effective ways to classify the nanoporous materials is measuring the diameter size of their pores, because numerous properties, which is interested in applications, determine by pore sizes such as adsorption and diffusion. According to IUPAC definition, nonporous materials can be classified in three main subgroups depending on their pore dimension (d): a- Micro porous materials d< 2nm, the size of the pores is small. These pores can host a tiny molecules, such as gas molecules, so they usually used in gas-storage materials and filtering membranes. These materials which have micropores appears high interaction properties and slow diffusion kinetic. b- Mesoporous materials 2

According to the pore sizes, these materials are usually used in systems such as adsorbing liquid or vapor systems or as catalyst systems. The diffusion kinetic depends on capillarity and the interactions happened between the wall and molecules after the pore filling. c- Macroporous materials d>50 nm, the pores in these materials are very large so these materials could host very big molecules such as biomolecules, polyaromatic systems. According to the pore size, these materials are usually used as store system and catalysis systems to the quick diffusion of chemical species in the pore system. According to many studies of the size and shape of the porous materials in the real systems, the pores could not possess homogenous pore sizes and shapes. In this case, the microporous materials could possess an additional mesopores due to random grain packing, and mesoporous materials could have an additional macropores due to the same reason of the micropores or could have an additional microporoses caused by the continuous network, and the macroporores could possess an additional pores according to the same reasons.

These factors should be taken into consideration when materials are classified according to their homogeneity. A material possessing just one type of pore, even when the pores are disordered, might be more homogenous than one having just a fraction of nicely ordered pores. 2.      Geometry of pores In this classification, the dimensionality is depending on the shape and dimension of the pores. For example, if there pores with one or more dimensions are not in nanoscale range so the classification can depend on the dimensions. The appearance of this classification is due to shape and dimensions of the pores and plays a vital role in the behavior and application of the the materials as illustrated in figure 1: