In the last two decades mesoporous materials having pore dimensions between 2 and approximately 50 nm have emerged. This group has established itself as an important class of solid-state materials with a huge and still constantly growing number of new congeners with pores on the nano- to mesoscale. These can be broadly classified into inorganic, organic and metal–organic types. Nevertheless, hybrids of these compositions have even been realized, extending the diversity in the chemical composition of such mesoporous solids further still. Besides their different chemical composition, the pore morphology, geometry and pore dimensions make these materials outstanding with respect to, e.g., catalytic reaction processes, in the area of sensorics, photonics and gas storage. In the realm of gas storage, mesoporous metal–organic frameworks (MOFs) appeared on the scene a couple of years ago and have quickly emerged as most-promising highly meso- and macroporous materials exhibiting enormous pore volumes with inner surface areas comparable with bare nanoparticles and thus coming close to the ultimate adsorption limit for solid materials.