Graphitic Carbon Nitride Nanosheets Decorated with Cu-Doped Carbon Dots for the Detection and Degradation of Phenolic Pollutants

The heterogeneous Cu-based solid catalysts have attracted enormous attention of researchers in different potential applications. In this work, a graphitic carbon nitride/copper-doped carbon dots (g-C3N4/Cu-CDs) nanocomposite with both intrinsic peroxidase- and oxidase-like (POD- and OXD-like) activities was successfully prepared. Due to the synergistic catalytic enhancement and electron transmission provided by g-C3N4, both POD- and OXD-like activities of g-C3N4/Cu-CDs were significantly improved compared with those of g-C3N4 and Cu-CDs. Moreover, upon the addition of H2O2, g-C3N4/Cu-CDs could catalyze the oxidation of colorless o-phenylenediamine (OPD) to form a yellow fluorescent product 2,3-diaminophenazine (DAP) with yellow fluorescence. Interestingly, the OPD + H2O2 + g-C3N4/Cu-CDs system could be inhibited by phenolic compounds, which could efficiently decrease the DAP fluorescence. Based on this, a method for the quantitative detection of total phenolic substances was established. Meanwhile, the use of OXD-like activity of nanocomposites was extended for the degradation of phenols (e.g., 2-CP), which showed a good degradation efficiency. Based on the result that the conversion of Cu+/Cu2+/Cu0 plays pivotal roles in promoting the generation of radicals (i.e., •OH and •O2–), a possible catalytic mechanism of g-C3N4/Cu-CDs was deduced. These findings showed that the proposed g-C3N4/Cu-CDs exhibit great potential to become a green catalyst for the degradation of phenolic pollutants in the environment.