Applications of silica-based Microporous and Mesoporous materials for drug delivery

Porous Materials: Porous material may be defined as material having voids. On the basis of size porous materials may be divided into four types. These are given as follows:

1. Microporous Materials: These have pore diameters of less than 2 nm. Examples of microporous materials include zeolite and metal-organic frameworks.
   1. Mesoporous Materials: These have pore diameters between 2 nm and 50 nm. Some kinds of silica and alumina that have similarly-sized fine mesopores are included in mesoporous materials. Mesoporous oxides of niobium, titanium, and tin have also been reported. According to the IUPAC, a mesoporous material can be disordered or ordered in a mesostructure.
   2. Macro Porous Materials: These have pore diameters of more than 50 nm. Macro pores may also be described in different way. For example, surface chemists define macropores as cavities that are greater than 50 nm
   3. Nonporous Materials: These consist of regular organic or inorganic framework supporting a regular, porous structure. The size of the pores is generally 100 nanometer or smaller. Most nanoporous materials can be classified as bulk materials or membranes. Activated carbon and zeolites come under the category of bulk nanoporous materials.