Cu(II) supported on Chitosan/LDH/Fe3O4 magnetic nanocomposite as an effective heterogeneous nanocatalyst for synthesizing bis(indolyl) methanes under ultrasonic conditions

Chitosan is a natural, nontoxic biopolymer with amine and hydroxyl functional groups which make it easy for chitosan molecules to form intermolecular and intramolecular hydrogen bonds. In that context, the present study reports Cu(II) supported on Chitosan@MgCuAl-LDH@Fe3O4 magnetic nanocomposite (Fe3O4@MgCuAl-LDH@CS/Cu(II)) as an effective and a novel heterogeneous catalyst to perform electrophilic substitution reaction between indoles and aromatic aldehydes to yield bis(indolyl)methane derivatives (BIMs) in shorter reaction time under ultrasonic conditions. Copper ions were mainly adsorbed onto the core-shell magnetic nanocomposite (Fe3O4@MgCuAl-LDH) modified with chitosan by the chelating capacity of chitosan and LDH. The catalyst's physicochemical properties and morphological structure were characterized using advanced analytical tech-niques, including XRD, FT-IR, FESEM, HRTEM, TGA, VSM, ICP-OES and EDX. Overall, the results show that Sonication significantly enhanced the catalytic performances compared to conventional heating. Also, the pre-pared catalyst could be easily separated from the solution using an external magnetic field and reused up to nine times without considerable leaching or loss in its catalytic activity.

Automated summary

A novel heterogeneous catalyst based on Chitosan@MgCuAl-LDH@Fe3O4 magnetic nanocomposite (Fe3O4@MgCuAl-LDH@CS/Cu(II)) was reported for the electrophilic substitution reaction between indoles and aromatic aldehydes under ultrasonic conditions. The catalyst showed enhanced catalytic performances compared to traditional heating and could be easily separated and reused multiple times without significant loss in its catalytic activity.