Efficient aerobic oxidation of benzyl alcohols using a magnetically recoverable Ni/nitrogen-containing carbon nanocomposite

Abstract

A magnetically recoverable nickel nanoparticle catalyst supported on polyaniline-derived carbon (Ni/PDC) was developed for the aerobic oxidation of benzyl alcohols. Polyaniline-derived carbon provides a nitrogen-containing carbon framework that facilitates the stabilization and uniform dispersion of nickel nanoparticles. The catalyst was synthesized via a hydrothermal method, and the reactions were carried out in isopropanol using molecular oxygen as the oxidant. Structural and surface characterization confirmed the presence of metallic Ni⁰ together with oxidized nickel species within the nitrogen-containing carbon framework, which likely facilitates oxygen activation and promotes the oxidation process. The catalyst exhibited good activity toward a variety of substituted benzyl alcohols and showed tolerance to different functional groups. Moreover, the catalyst could be readily separated from the reaction mixture using an external magnet and reused for seven consecutive cycles without significant loss of catalytic activity. Gram-scale reactions further demonstrated the practical applicability of this catalytic system. Overall, the Ni/PDC catalyst provides a cost-effective and reusable nickel-based system for the synthesis of value-added aromatic aldehydes such as vanillin, anisaldehyde, and indole-3-carboxaldehyde under mild aerobic conditions, and its sustainability profile was further assessed using the CHEM21 green metrics toolkit.