Creation of N-C=O active groups on N-doped CNT as an efficient CarboCatalyst for solvent-free aerobic coupling of benzylamine

The creation of specific catalytic functionalities in the nanocarbon materials is an important approach to develop the metal-free nanocarbon materials (carbocatalysts). We report herein a functionalization strategy by treatment of N-doped carbon nanotubes (NCNT) with ozone/water to create oxygen groups nearby the N groups (N-C=O). These groups, different from those present in conventionally oxidized NCNT, show peculiar catalytic behavior. The N atom adjacent to carbonyl group (N-C=O) modifies the reactivity of carbonyl towards C-H activation and simultaneously activate O2 molecule for bifunctionality. Efficient performance for oxidative coupling of benzylamine to imine (>99% imine selectivity) can be obtained under solvent-free conditions at ambient pressure. The benzylamine productivity reaches as high as 131.3 μmol m−2 h−1, which is the highest among any other reported carbon-based catalysts. This work not only highlights a sustainable strategy for tuned surface chemistry of carbon materials by using mild ozonation process, but also reports a novel green aerobic synthesis method of benzylamine using tailored metal-free carbon nanomaterials. © 2020 Elsevier Ltd