If we use lithium batteries, non-stoichiometry of bonding lithium is clearly evident ((inclusion, or intercalation). Single crystals of silicon, the basis of modern electronics, receive their desired characteristics after successful doping by respective additives, again in non-stoichiometric proportions. Zeolites are the next example and the ‘organic’ option is among the precious, in terms of possible applications, materials known in the chemical literature since 1970ths  

Porous molecules are not a rarity, biological chemistry may serve as the valuable source of this sort of matter, like starch component, amylose, and the products of its enzymatic degradation – cyclodextrins. And in recent decades numerous synthetic molecules possessing internal pores have been reported: calixarenes, cucurbiturils, cavitands, crowns, to mention just a few examples.

The paper will concentrate on physico-chemical characteristic of porous materials, including flexibility of their crystal structures which allows ‘engineering’ of sorption/desorption procedures aimed at optimization of solid materials towards a given practical use. Structural and thermochemical experimental data will be discussed jointly with the examples of practical application: separation of organic mixtures in extraction and chromatographic systems, storage of selected species and stabilization of unstable or reactive species.

The illustration will be selected from two major classes of porous materials: solvates of coordination compounds in the form of inclusion compounds and selected molecular hosts (cyclodextrins) presenting infinite number of possible chemical modifications thus enabling design and control of structure/properties relationships.

Studies of fine structural effects accompanying sorption/desorption processes will be discussed from the above mentioned point of view and as aimed at engineering of materials of desired properties.

Supramolecular hydrates will be mentioned as a special class of porous materials.