Sulphur-doped graphene as metal-free carbocatalysts for the solventless aerobic oxidation of styrenes

•Pyrolysis of λ-carrageeenan and exfoliation lead to S-doped graphene.•XP spectroscopy shows the presence of two types of sulphur atoms.•S-doped graphene is able to promote the aerobic oxidation of styrenes.

Pyrolysis of λ-carrageenan at 1000 °C and subsequent exfoliation lead to a S-doped graphene [(S)G]. Increasing pyrolysis temperature to 1200 °C or the use of other carrageenans with lower sulphate content results in the failure of S doping. XPS confirms the presence of S atom (4.5%) with environments alike sulphide and sulphoxide. (S)G promotes the aerobic oxidation of styrenes to their corresponding benzaldehydes accompanied by lesser amounts of styrene oxide. In contrast, under the same experimental conditions reduced graphene oxide exhibits a negligible activity. (S)G was reused with almost coincident catalytic performance.

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