▎ 摘　　要

Graphene oxide, decorated with surface oxygen ffinctionalities, has emerged as an alternative to precious-metal catalysts for many reactions. Herein, we report that graphene oxide becomes superactive for C-C coupling upon incorporation of a highly oxidized surface associated with Bronsted acidic oxygen functionality and defect sites along the surface and edges. The resulting improved graphene oxide (IGO) demonstrates significantly higher activity over commonly used framework zeolites for the upgrade of low-carbon biomass furanics to high-carbon fuel precursors. A maximum 95% yield of C-15 fuel precursor with high selectivity is obtained at low temperature (60 degrees C) and neat conditions via hydroxyalkylation/alkylation (HAA) of 2-methylfuran (2-MF) and furfural. Coupling of 2-MF with carbonyl compounds ranging from C-3 to C-6 produces precursors of carbon numbers 12 to 21 with a high yield. The catalyst regains nearly full activity upon regeneration. Extensive microscopic and spectroscopic characterization of the fresh and reused IGO carbocatalysts indicates that defects and the enhanced oxygen content are strongly correlated with the high activity of IGO. Density functional theory calculations reveal defects at carbonyl sites as suitable Bronsted acidic oxygen functional groups. A plausible reaction mechanism is also hypothesized.