Kraft lignin derived S and O co-doped porous graphene for metal-free benzylic alcohol oxidation†
Using a metal-free carbon-based catalyst for aerobic oxidation of benzylic alcohols to aldehydes is still a great challenge under mild conditions. Here, we report the fabrication of high-quality graphene (G1000) using waste Kraft lignin as a sustainable feedstock via carbonization, which showed excellent performance in oxidation of benzylic alcohols. The as-prepared hierarchically porous graphene primarily consists of 1 to 4 atom layers, and large amounts of inherent S and O-containing groups are chemically doped into the graphene lattice. The G1000 catalyst exhibited complete conversion of benzyl alcohol and 95.9% yield of benzaldehyde at 120 °C and 0.5 MPa O2. Density functional theory (DFT) calculations reveal that the S and O co-doped graphene exhibits enhanced charge delocalization with ameliorated electron accepting capability, which facilitates the adsorption and activation of benzylic alcohols, thus promoting their catalytic oxidation in comparison to conventional graphene.