By thermal treatment in vacuum, graphite oxide prepared from Hummers' method was exfoliated and partially reduced. This procedure imparts the graphene oxide (GO) the high reactivity with 2,2,6,6-tetramethyl-piperidin-1-oxyl (TEMPO) as co-catalyst for selective oxidation of 5-hydroxymethylfrufural (HMF) to 2, 5-diformylfuran (DFF) under certain conditions (100% HMF conversion with HMF selectivity 99.6% at 80 wt.% GO loading, 1 atm air pressure). This study found that GO could function as an oxidant for anaerobic oxidation of HMF during which carboxyl groups in GO were reduced. Importantly, the partially reduced GO material could continue activate molecular oxygen during aerobic oxidation. Further study showed that oxygen functionalities in GO material had a crucial effect on the catalytic oxidation of HMF.By control experiments and molecular analogues tests, a plausible mechanism was proposed in which the high reactivity was attributed to the synergistic effect of the carboxylic acid groups and unpaired electrons at GO edge defects, with TEMPO as the co-catalyst and oxygen as the terminal oxidant.

Graphene oxide (GO), prepared by the modified Hummers method, was applied as a highly active and selective solid acid catalyst for oxidative transformation of furfural (FAL) into succinic acid (SA) with H2O2 as the oxidant. Over a GO catalyst, 88.2% yield of SA from FAL was achieved under relatively mild reaction conditions. By characterization of the prepared GO and various control experiments, the higher efficiency of GO than conventional catalysts was attributed to its unique atomic layered structure and suitable acidity. On the basis of the results in this work and previous reports, a reasonable reaction pathway was proposed. Different from other acid catalysts, it was suggested that the aromatic rings in GO and the edges decorated with −SO3H groups worked synergistically in FAL oxidation. The GO catalyst was found reusable, and only a slight decrease in the catalytic activity was observed after six cycles.

Graphene oxide, a metal-free carbon based material, was demonstrated to be an efficient and recyclable bifunctional catalyst in the direct synthesis of DFF from fructose.