Periodic mesoporous organosilicas (PMOs) represent an exciting new class of organic-inorganic nanocomposites targeted for a broad range of applications such as catalysis and sensing, separations, and microelectronics. Their hallmark is the presence of organic bridging groups incorporated into the channel walls of an ordered nanoporous structure, which represents a useful tool to finely tune the chemical and physical properties of the materials. We discuss the history of the discovery and development of the PMOs emphasizing the most important recent advancements regarding compositions and structures, morphologies, and properties. Furthermore, we present an outlook about the promising future perspectives of PMOs that result from the latest developments in this field.

Carbon dioxide capture from point sources like coal-fired power plants is considered to be a solution for stabilizing the Co 2 level in the atmosphere to avoid global warming. methane is an important energy source that is often highly diluted by nitrogen in natural gas. For the separation of Co 2 and CH 4 from n 2 in flue gas and natural gas, respectively, sorbents with high and reversible gas uptake, high gas selectivity, good chemical and thermal stability, and low cost are desired. Here we report the synthesis and Co 2 , CH 4 , and n 2 adsorption properties of hierarchically porous electron-rich covalent organonitridic frameworks (PEConFs). These were prepared by simple condensation reactions between inexpensive, commercially available nitridic and electron-rich aromatic building units. The PEConF materials exhibit high and reversible Co 2 and CH 4 uptake and exceptional selectivities of these gases over n 2 . The materials do not oxidize in air up to temperature of 400 °C.

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A periodic mesoporous organosilica composed of interconnected three-ring [Si(CH2)]3 units built of three SiO2(CH2)2 tetrahedral subunits is reported. It represents the archetype of a previously unknown class of nanocomposite materials in which two bridging organic groups are bound to each silicon atom. It can be obtained with powder and oriented film morphologies. The nanocomposite is self-assembled from the cyclic three-ring silsesquioxane [(EtO)2Si(CH2)]3 precursor and a surfactant mesophase to give a well-ordered mesoporous framework. Low dielectric constants and good mechanical stability of the films were measured, making this material interesting for microelectronic applications. Methylene group reactivity of the three-ring precursor provides entry to a family of nanocomposites, exemplified by the synthesis and self-assembly of [(EtO)2Si(CHR)][(EtO)2Si(CH2)]2 (where R indicates iodine, bromine, or an ethyl group).

Periodic mesoporous organosilica (PMO) thin films have been produced using an evaporation‐induced self‐assembly (EISA) spin‐coating procedure and a cationic surfactant template. The precursors are silsesquioxanes of the type (C2H5O)3Si–R–Si(OC2H5)3 or R′–[Si(OC2H5)3]3 with R = methene (–CH2–), ethylene (–C2H2–), ethene (–C2H4–), 1,4‐phenylene (C6H4), and R′ = 1,3,5‐phenylene (C6H3). The surfactant is successfully removed by solvent extraction or calcination without any significant Si–C bond cleavage of the organic bridging groups R and R′ within the channel walls. The materials have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X‐ray diffraction (PXRD), and 29Si and 13C magic‐angle spinning (MAS) NMR spectroscopy. The d‐spacing of the PMOs is found to be a function of R. Nanoindentation measurements reveal increased mechanical strength and stiffness for the PMOs with R = CH2 and C2H4 compared to silica. Films with different organic‐group content have been prepared using mixtures of silsesquioxane and tetramethylorthosilicate (TMOS) precursors. The dielectric constant (k) is found to decrease with organic content, and values as low as 1.8 have been measured for films thermally treated to cause a “self‐hydrophobizing” bridging‐to‐terminal transformation of the methene to methyl groups with concomitant loss of silanols. Increasing the organic content and thermal treatment also increases the resistance to moisture adsorption in 60 and 80 %‐relative‐humidity (RH) environments. Methene PMO films treated at 500 °C are found to be practically unchanged after five days exposure to 80 % RH. These low dielectric constants, plus the good thermal and mechanical stability and the hydrophobicity suggest the potential utility of these films as low‐k layers in microelectronics.