High Cobalt Content Mesoporous Silicas

Abstract

Silica-based MCM-41-like mesoporous materials with high cobalt content (∞ g Si/Co g 23) have been synthesized through a one-pot surfactant-assisted procedure from aqueous solution using a cationic surfactant (CTMABr ) cetyltrimethylammonium bromide) as structural directing agent, and starting from molecular atrane complexes of Co and Si as inorganic hydrolytic precursors. This preparative technique allows optimizing the dispersion of the Co guest species in the silica walls. The mesoporous nature of the final materials is confirmed by XRD, TEM, and N 2 adsorption-desorption isotherms. They display unimodal and relatively narrow pore size distributions, whereas their pore array evolves from ordered hexagonal (H 0 ) to wormhole-like (W) as the Co content increases. A careful spectroscopic (UV-visible and NMR) and magnetic study of these materials shows that, regardless of the Si/Co ratio, Co atoms are organized in well-dispersed, uniform CoO nanodomains (ca. 3 nm) partially embedded within the silica walls. These materials, which show superparamagnetic behavior, can be referred to as mesoporous CoO-MCM-41 nanocomposites.

Catalytic aerobic oxidation of ethylbenzene over Co/SBA-15

“…The blue color of Co/SBA-15 is also a fingerprint of tetrahedral Co(II)O 4 sites. In addition, the absence of peaks at around 480 and 506 nm indicates the absence of Co(II) in an octahedral environment [18], and the absence of a peak at 410 nm indicates the absence of Co(III) [19]. As we known Co(OAc) 2 can convert to Co 3 O 4 after calcination at 773 K in air, but it converted to CoO after impregnation on SBA-15 in our work.…”

High‐Zirconium‐Content Nano‐Sized Bimodal Mesoporous Silicas

“…[45] In fact, such a method has allowed us to successfully prepare a diversity of unimodal mesoporous single and mixed oxides, including the Zr-MCM-41 materials, [36] working under strongly basic conditions (pH = [11][12]. [51][52][53][54][55][56] In contrast, in the case we are dealing with, the synthesis pH was buffered at ca. 9.…”

Catalytic Oxidation of Oleic Acid in Supercritical Carbon Dioxide Media with Molecular Oxygen

“…They are assigned to 4 A 2 (F) ? 4 T 1 (P) triplet transition of Co(II) ions in the tetrahedral environments [36]. MnMCM-41 shows two prominent absorption bands one at 270 nm assigned for charge transfer transitions (oxygen to trivalent manganese) in tetrahedral coordination and other at 500 nm due to the A 1g ?…”