Aerobic Oxidation of Fluorene to Fluorenone over Copper-Doped Co₃O₄ with a High Specific Surface Area

Abstract

Copper-doped Co 3 O 4 with a high specific surface area has been prepared by using mesoporous silica KIT-6 as a hard template, which showed exceptional catalytic performance (99% conversion of fluorene and 99% selectivity of fluorenone) for catalytic oxidation of fluorene to fluorenone using molecular oxygen as the oxidant in the absence of a radical initiator or other cocatalysts. Characterization results of N 2 adsorption− desorption, X-ray diffraction, and transmission electron microscopy of the samples revealed the ordered mesoporous structure and increased specific surface area. X-ray photoelectron spectroscopy and O 2 temperatureprogrammed desorption results showed the increased surface cobalt, Co 3+ / Co 2+ ratio, and oxygen species. The H 2 temperature-programmed reduction also indicated that the redox ability could be improved by doped copper in Co 3 O 4 , which all facilitated the aerobic oxidation reaction.

Novel Bamboo-Mediated Biosynthesis of MnOx for Efficient Low-Temperature Propane Oxidation

“…Although supported noble metal catalysts show good oxidation activity, their high price and poor thermal stability limit their practical applications. Transition-metal oxides have attracted scholarly attention because of some superior properties, such as high catalytic performance, low cost, and good stability. − MnO x is very promising as a catalyst candidate among transition-metal oxides on account of its environmental friendliness, facile reducibility, and various oxidation states (Mn 2+ , Mn 3+ , Mn 4+ ). − …”

Dioxygen-triggered oxidation of benzylic C–H bonds: insight on the synergistic effect of Cu–Fe bimetallic oxide

“…Some heterogeneous catalysts, such as Au-pDA-rGO, Cu/Co 3 O 4 , Mn@SiO 2 /Al 2 O 3 , Cu-ZrPO, Cu-CuFe 2 O 4 @HKUST-1, and MnSBA-15, have been catalytically tested for the oxidation of benzylic C-H bonds. 10,[16][17][18][19][20] Cheap and abundant transition metal oxides can be considered a promising alternative for the oxidation of C(sp 3 )-H bonds using molecular oxygen as an oxidant. Luo et al reported that a Cu-doped Co 3 O 4 catalyst with redox properties could improve the oxidation of fluorene to fluorenone at 90 °C under 1 MPa O 2 .…”

“…Luo et al reported that a Cu-doped Co 3 O 4 catalyst with redox properties could improve the oxidation of fluorene to fluorenone at 90 °C under 1 MPa O 2 . 18 Xamena et al reported a Co-Ni-BTC catalyst for the oxidation of cumene to cumene hydroperoxide at 90 °C under a p(O 2 ) of 0.4 MPa (7 h, conversion: 30%, selectivity: 91%). 21 Hutchings et al used an Au-Pd/C catalyst for the oxidation of C(sp 3 )-H bonds in toluene at 160 °C under 1 MPa O 2 , and the catalyst exhibited 4.4% conversion and 76% selectivity towards benzyl benzoate.…”

Copper‐Chitosan Beads as Efficient and Recyclable Heterogeneous Catalysts for C−H Oxidation and C−X Amination

“…[14] The selective oxidation of inert sp 3 CÀ H bond by transition metal catalysts has been employed as alternative catalytic systems for the synthesis of benzylic ketones under milder conditions. Examples include homogeneous catalysts, such as ReOCl 3 (OPPh 3 )(SMe 2 ), [15] pyridine-bridge pincer-type benzimidazole Ru complexes, [16] and Pd aminopyridine complexes, [17] as well as heterogeneous ones, Cu and Fe modified MCM-22, [18] Mn-containing porous silica, [19] LaMO 3 (M = Cr, Co, Fe, Mn, Ni), [20] hydrotalcite-related materials, [21] copper-doped Co 3 O 4 , [22] cobalt triazine complexes modified silica, [23] and MnO 2 . [24] Here, we demonstrate the effectiveness of our catalyst system derived from the incorporation of copper species onto chitosan beads in the oxidation of alkyl aromatic compounds to ketones with TBHP under mild condition.…”