Cu₂O‐CuO/Chitosan Composites as Heterogeneous Catalysts for Benzylic C−H Oxidation at Room Temperature

Abstract

Recently, in catalysis, chitosan has been exploited as a macrochelating ligand for metal active species due to the presence of various functional groups in its structure. Moreover, copperbased catalysts are classified as one of the most environmentally friendly catalytic systems and their use for the oxidation of alkylarene has not been established much. Therefore, in this work, the hydrothermal synthesis of copper oxidechitosan composites as heterogeneous catalysts for the benzylic CÀ H oxidation of alkylarene was investigated. Characterization results reveal mixed phases of CuO and Cu 2 O, inferring the ability of chitosan to act as a reducing sugar under the hydrothermal condition. The pre-existing interaction between copper species and chitosan as well as the co-existence of the Cu 2 O and CuO structures give rise to the efficient performance of the catalysts. The synthesized composites exhibit high activity for the oxidation of fluorene to 9-fluorenone at room temperature and small catalyst loading (1 mol % of Cu, > 90 % conversion and 100 % selectivity). Superior TOF was observed, and a good scope of substrates can be converted to corresponding ketones in 48-97 % yields with these copper oxide-chitosan catalysts. In addition, the catalysts can be used for up to nine cycles without significant decrease of the activity.

A suitably fabricated ternary nanocomposite (Cu-CuO@rGO-SiO2) as a sustainable and common heterogeneous catalyst for C–S, C–O and C–N coupling reactions

“…[19][20][21][22][23][24][25][26] Moreover, the presence of copper species in the form of Cu 2 O-CuO/Cu, Cu 2 O-CuO and Cu-Cu 2 O-CuO leads to distinctive catalytic activity. [27][28][29][30][31][32] Furthermore, their catalytic activity could be improved if they are immobilized on suitable materials having a high surface area. These include mesoporous and microporous materials like silica, zeolites, metal-organic frameworks (MOFs), etc.…”

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

“…Over the past decades, expensive tert-butyl hydroperoxide (TBHP) or hydrogen peroxide (H 2 O 2 ) was extensively used as an oxidant for the oxidation of aromatic benzyl compounds. [6][7][8][9][10] Compared to the above-mentioned oxidants which are toxic and environmentally unfriendly, molecular oxygen is an inexpensive and greener oxidant. 11,12 Therefore, the use of molecular O 2 (e.g.…”

Design, Synthesis and Characterization of Palladium‐Functionalized Covalent Organic Framework and Its Application as Heterogeneous Catalysis for C−H Arylation of Azoles

“…Compared to homogeneous catalysts, heterogeneous ones are arguably more attractive in the chemical industry due to their easier separation and recycling. [23][24][25] Although a large number of carriers such as natural species, inorganic materials, clays, magnetic material, biochar, organic polymers and metal-organic frameworks, have been applied as the support for constructing heterogeneous catalysts, [26][27][28][29][30] the stability, recyclability, leaching, and economic, environmental issues need to be further improved.…”