Microporous cobaltporphyrin covalent polymer mediated Co3O4@PNC nanocomposites for efficient catalytic C-H bond activation

Co3O4@PNC was synthesized by two steps. Firstly, porphyrin and cobalt porphyrin coupled with 1,4-phenylenebisboronic acid to form porous polymer by Suzuki-Coupling reaction. Then, the polymer was subjected to pyrolysis to form Co3O4@PNC, which shows excellent performance in catalytic oxidation of C–H bonds. [Display omitted] •Co3O4 nanoparticles generate in situ from heat treatment of cobaltporphyrin polymer.•Co3O4 nanoparticle wrapped in the porphyrin-polymer-like nitrogen-carbon materials.•Co3O4@PNC-400 has excellent catalytic activity for the aerobic oxidation of C–H bonds.•The defect caused by the migration of cobalt can improve the catalytic activity. A Cobalt porphyrin conjugated porous polymer (Co/PCP) was obtained by hybrid polymerization of a mixture of Co(II)(5,10,15,20-tetrakis(4-bromophenyl)-21H,23H-porphyrin) (CoTBPP) and 5,10,15,20-tetrakis(4-bromophenyl)-21H,23H-porphyrin (TBPP) (3:7 M ratio) with the coupling reagent of p-phenyldiboric acid. This Co/PCP was carbonized at 400 °C and the obtained catalyst (denoted as Co3O4@PNC-400) was composed of Co3O4 nanoclusters wrapped in the nitrogen-carbon materials. This catalyst has an extremely high catalytic activity for the aerobic oxidation of C–H bonds. It can efficiently catalyze the oxidation of the C–H bonds in toluene and cyclohexane with high conversion and high selectivity of (alcohol + aldehyde), (alcohol + ketone) compounds, respectively. When heat-treated at 400 °C, the porous framework structure of the porphyrin polymer was partially retained, and the highly active Co3O4 nanoclusters were generated in situ. The reaction of CN to CN and connection with the Co3O4 nanoclusters also occurred. Co3O4@PNC-400 has obvious synergistic catalytic effect between Co3O4 and nitrogen-carbon framework during the catalytic reaction. The defective structure caused by the migration of cobalt also greatly improved the catalytic activity. Co/PCPs with different cobalt contents were also synthesized and heat treated at different temperature. These catalysts were a new type of efficient C–H oxidation catalysts with excellent potential application value.