Periodic Mesoporous Silicas and Organosilicas: An Overview Towards Catalysis

Abstract

Micelle-templated mesoporous and organicinorganic hybrid mesoporous materials are important in many fields of material research, especially for hosting catalysts in confined space. Among this class, the recent discovery of periodic mesoporous organosilicas (PMOs) represent an exciting new group of organic-inorganic nanocomposites targeted for a broad range of applications ranging from catalysis to microelectronics. Compared to the earlier generation of organic-inorganic hybrid mesoporous samples, obtained by the cocondensation reaction or by the grafting reaction, PMOs represent the right combination of organic and inorganic groups in the frame wall positions. This article reviews the current state of art in organic-inorganic hybrid mesoporous material research with special emphasis over periodic mesoporous organosilica materials having various redox centers (Ti, V, Cr) suitable for oxidation reactions as well as acidic sites (Al, -SO 3 H) for the organic transformation of bulky molecules.

Periodic mesoporous organosilicas with bis(8-quinolinolato) dioxomolybdenum(VI) inside the channel walls

“…1, inset), due to the enhanced contrast in the electron density after template removal [23]. No peaks assigned to metal species present in the 2h range of 10-40°Can be ascribed to the uniform distribution of Mo complexes in the amorphous walls [8,24]. TEM images of the PMO materials recorded using a parallel view to the pores exhibit honeycomb structures while the images recorded using a perpendicular view show parallel fringe structures (Fig.…”

“…The combined advantages of ordered mesoporous structure, unique pore-wall functionality, and the marriage of organic chemistry and inorganic materials chemistry offer PMOs fascinating new possibilities and potential applications [6,7]. One of the main aspects in this area is, therefore, to synthesize desired organometallic functionalized PMOs for extension of their applications in heterogeneous catalysis [8], especially in olefin epoxidations.…”

Nature of active vanadium nanospecies in MCM-41 type catalysts for olefins oxidation

“…The introduction of vanadium species in the MCM-41 structure gives Raman bands at 269, 335, 920 and 1018 cm À1 . Thus, Raman band of 1018 cm À1 corresponds to the stretching frequency of a terminal of V]O group bonded to the silicate MCM-41 [6,33]. In addition, the Raman band at 269 cm À1 can be ascribed to the VeOeV bending mode and the bands centered around 335 and 920 cm À1 may correlate with the VeOeV stretching vibrations [6,33]; these bands are increased with increasing content of V. Finally, the absence of typical bands to 995, 703 and 530 cm À1 implies that no crystalline V 2 O 5 is formed in the samples, which is in accordance with XRD [25] and UVeVis-RD results.…”

Optimization of key parameters for effective vanadium substitution into cubic SBA-16 in the presence of co-surfactant at low acidity: Application in the selective oxidation of ethylbenzene

“…Such synthesized V-MCM-41 was found to show high catalytic activity in the oxidative dehydrogenation of propane than that prepared by the direct hydrothermal method. Shylesh et al [5] synthesized vanadium-containing mesoporous molecular sieves synthesized by three different routes by the direct hydrothermal, grafting and immobilisation methods. The nature of vanadium species formed over the MCM-41 support surface was well characterized by them using various physico chemical techniques such as XRD, N 2 sorption isotherms, UV-vis and TPR.…”