A microporous material is a material containing pores with typical sizes less than 2 nm in diameter. Microporous materials, like mesoporous materials, are a subset of nanoporous materials. Examples of microporous materials include zeolites and metal-organic frameworks. Porous materials are classified into several kinds by their size. The recommendations of a panel convened by the International Union of Pure and Applied Chemistry (IUPAC) are:Microporous materials have pore diameters of less than 2 nm. Mesoporous materials have pore diameters between 2 nm and 50 nm. Macroporous materials have pore diameters of greater than 50 nm.