Small-sized biomass-derived hydrothermal carbon with enriched oxygen groups quickens benzene hydroxylation to phenol with dioxygen

Metal-free carbon materials have attracted growing attention in terms of green and sustainable catalysis processes that could avoid potential metal leaching but usually suffered from inferior activity to metal-loaded counterparts. In this work, we constructed an efficient carbon catalyst via hydrothermal carbonization of biomass-derived feedstock glucose under relatively low temperature (180 °C). The resultant carbon material possessing abundant surface oxygen species effectively catalyzed the benzene hydroxylation with dioxygen (O₂), a desirable but very difficult alternative process for producing the important bulk chemical phenol. A considerably high phenol yield of 13.1% was achieved within 4 h, a reaction time much shorter than all the previous metal-free catalysts and even shorter than most efficient metal-based catalysts. The fast reaction is determined by the formation of small-sized primary carbon particles with the abundant surface oxygen species, for which the adsorption enhancing effect in the media of this heterogeneous process was experimentally evidenced.