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

Pyrolysis of X-carrageenan at 1000 degrees C and subsequent exfoliation lead to a S-doped graphene [(S)G]. Increasing pyrolysis temperature to 1200 degrees 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. (C) 2015 Elsevier B.V. All rights reserved.