Biogenic Magnetosomes as Magnetically Recoverable Catalysts for Benzyl Alcohol Oxidation

Biogenic magnetosomes are intracellular single-domain magnetic nanoparticles (MNPs) produced by Magnetospirillum gryphiswaldense MSR1, consisting of crystalline magnetite (Fe₃O₄) encapsulated within an organic membrane. Despite their controlled structure and widespread study in biomedical and magnetic applications, their use in catalysis has not been explored. Here, magnetosomes are demonstrated for the first time as heterogeneous catalysts for benzyl alcohol oxidation using hydrogen peroxide. Under aqueous batch conditions, catalytic performance was tested, varying catalyst loading and temperature. Among the loadings tested, the highest conversion was achieved using 5.2 mol % Fe₃O₄ equivalent, reaching 64 ± 4% after 24 h with 36 ± 5% benzaldehyde selectivity. At approximately matched Fe₃O₄ contents, this performance was broadly comparable to commercial Fe₃O₄, which produced 72 ± 2% conversion and 38 ± 3% selectivity. Temperature screening of magnetosome catalysts increased conversion up to 75 ± 11% at 85 °C with 30 ± 4% benzaldehyde selectivity. Meanwhile milder conditions improved selectivity to 43 ± 2% at the expense of lower conversion, reflecting the expected conversion/selectivity trade-offs seen in wider iron oxide-catalyzed peroxide systems. Catalytic recyclability was demonstrated over five reaction cycles, where magnetic recovery enabled the spent mixture to be removed and replaced without centrifugation or filtration. During these cycles conversion decreased only modestly from 71 ± 5% to 65 ± 4% with selectivity remaining between 33 and 38%. Overall, this work demonstrates that biogenic magnetosomes can function as catalytic materials and expands the potential applications of magnetotactic bacteria-derived nanostructures.