A simple and rapid functionalization of MOF via microwave-assisted one-pot synthesis afforded a Cu(ii)-Schiff-base-MOF as an efficient catalyst for olefin oxidation.
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.
Uniform millimeter‐sized copper‐incorporated chitosan beads were easily prepared via a simple synthetic method as efficient bifunctional heterogeneous catalysts for C−H oxidation of alkylarenes to ketones and C−X amination of aryl halides with ammonia. These potent catalysts were compatible to various substrates, resulting in 2–97 and 39–99 % yields for the oxidation and amination reactions, respectively. Moreover, we highlight the dual roles of chitosan that it not only served as a versatile support to enhance the catalytic performance of copper active species, but it also acted as a base to promote the catalytic reactions. The catalysts are robust and could be employed under conventional heating or microwave irradiation for several times without deactivation or deformation. The bead shape of the catalysts provides easy separation and recyclability. Thus, chitosan and this preparation method may be exploited in the development of other transition metal catalyst beads for valuable organic reactions.
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