Enhanced catalytic performance of magnetic Fe3O4-MnO2 nanocomposites for the decolorization of rhodamine B, reduction of 4-nitroaniline, and sp3 C-H functionalization of 2-methylpyridines to isatins

•MnO2, Fe3O4, and Fe3O4-MnO2 nanocomposites were synthesized using leaf extract of Perilla frutescens.•The synthetic protocol is cheap, fast, and ecofriendly.•Owing to the synergistic effect of Fe3O4 loaded on MnO2, the synthesized nanocomposites showed strong catalytic ability.•The magnetic Fe3O4-MnO2 nanocomposites were reused for five consecutive reactions without any significant loss of catalytic ability.

A novel biosynthesized nanocatalyst, iron oxide-loaded manganese dioxide nanocomposites (Fe3O4-MnO2 NCs), was fabricated with the aid of a Perilla frutescens leaf extract. The MnO2 is composed of numerous nanoflakes radiating from the center, which results to a flowerlike structure. A change in the flowerlike morphology of MnO2 in Fe3O4-MnO2 NCs was observed due to the distribution of Fe3O4 nanoparticles on the surface of MnO2. To check the catalytic performance of the synthesized NCs, they were utilized as a catalyst for the decolorization of rhodamine B (RhB), reduction of 4-nitroaniline (4-NA), and sp3 C-H functionalization of 2-methylpyridines to isatins for the synthesis of azaarene-substituted 3-hydroxy-2-oxindole derivatives. The Fe3O4-loaded MnO2 exhibited enhanced catalytic ability over MnO2. Moreover, the nanocomposites could be recovered by a magnetic separation technique and reused for five consecutive reactions without significant loss of catalytic ability.

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