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

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 Co 3 O 4 @PNC-400) was composed of Co 3 O 4 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 Co 3 O 4 nanoclusters were generated in situ. The reaction of C N to C N and connection with the Co 3 O 4 nanoclusters also occurred. Co 3 O 4 @PNC-400 has obvious synergistic catalytic effect between Co 3 O 4 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.