Synthesis, characterization and heterogeneous catalytic application of copper integrated mesoporous matrices

Abstract

Ordered copper integrated mesoporous silicate catalysts (CuMSC) have been synthesized by the utilization of the amphiphilic tri-block copolymer pluronic F127 as a structure directing agent (SDA) under acidic aqueous conditions. The mesophase of the materials was investigated using small-angle powder X-ray diffraction and transmission electron microscopic (TEM) image analysis. N2 adsorption-desorption studies show that the BET surface area of CuMSC (214-407 m(2) g(-1)) is lower than that of pure silica (611 m(2) g(-1)) and has smaller average pore dimensions (4.0-5.0 nm), both prepared following the same synthetic route. The reduction of pore size and surface area points to incorporation of copper within the silicate network. FEG-SEM results suggest that the materials have a plate-like morphology and are composed of very tiny nanoparticles. EDS surface chemical analysis was utilized for the detection of the distribution of Si, O and Cu in the matrix. The FT IR spectral study suggests the complete removal of the surfactants from the calcined materials and the presence of Si-O-Cu bonds for high nominal contents. X-ray photoelectron spectroscopy (XPS) and UV-vis reflectance spectra show the oxidation state of copper and coordination mode, respectively. These mesoporous materials display a good catalytic activity in the oxidation of cyclohexane to cyclohexanone and cyclohexanol in the presence of the green oxidant hydrogen peroxide. The maximum yield (cyclohexanone and cyclohexanol) was ca. 29% and the TON (turnover number) was 276 under optimal reaction conditions. The good catalytic activity could be attributed to the large surface area and the presence of a high number of active sites located at the surface of the material, as well as to its stability. The catalysts showed negligible loss of activity after five cycles.

Activating effect of cerium in hydrotalcite derived Cu–Mg–Al catalysts for selective ammonia oxidation and the selective reduction of NO with ammonia

“…Moreover, a very broad band centered at about 745-790 nm, is attributed to the d-d transition in Cu 2? located in a distorted octahedral coordination [25,26]. The insert in Fig.…”

New Trends in Oxidative Functionalization of Carbon–Hydrogen Bonds: A Review

“…Polynuclear metal complexes containing voluminous organic [63,66,118,119,[129][130][131]186,[213][214][215][216][217][218][234][235][236][237][238][239][240][241] or siloxane [221][222][223][224][225][226][227][228] ligands are also very efficient in oxidations of organic compounds including saturated hydrocarbons with peroxides. For example, dinuclear copper complex 11 [221,224] and hexairon complex 15 (for the structure, see Figure 9) affording the products of cyclohexane oxidation in a very high yield of 46% (see Figure 10 [226]) can be considered as "inorganic models of methane monooxygenases."…”

“…Metal-organic frameworks (MOFs), or porous coordination polymers, have attracted the attention of chemists [229][230][231][232][233]. Pombeiro, Martins, Guedes da Silva [234][235][236][237][238], Kirillov [234,235,[239][240][241], and other scientists [242] synthesized various polynuclear complexes, coordination polymers, and derived metal integrated mesoporous matrices and demonstrated high catalytic activity of these materials in oxidations with peroxides. Figures 13-15 show the examples of such catalysts.…”

One-step fabrication of Fe-Si-O/carbon nanotube composite anode material with excellent high-rate long-term cycling stability

“…3b). According to the literature [7,32,33], the peak around 1058 cm À1 is ascribed to the asymmetric stretching mode of Si-O-Si of the tetrahedral [SiO 4 ] structure [32], while the one around 827 cm À1 to the Si-O-Si symmetric stretching mode and the one around 514 cm À1 to the O-Si-O bending mode [7,32,33], indicative of the presence of SiO 2 in the product. The peaks around 474 and 570 cm À1 are related to the characteristic bands of FeeO [33], and the one at 1720 cm À1 to the C]O stretch derived from the oxidized carbon.…”