title: 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.
authors.affiliation: Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal. pombeiro@tecnico.ulisboa.pt.
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Das
authors.forename: Sanghamitra
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Luís M F
authors.initials: LM
authors.lastname: Lopes
authors.forename: Laura M
authors.initials: LM
authors.lastname: Ilharco
authors.forename: Ana M
authors.initials: AM
authors.lastname: Ferraria
authors.forename: Ana M
authors.initials: AM
authors.lastname: Botelho do Rego
authors.forename: Armando J L
authors.initials: AJ
authors.lastname: Pombeiro