Cobalt-based zeolitic imidazole framework incorporated with well-dispersed bimetallic nanoparticles/ions as a multifunctional nanozyme for the degradation of environmental pollutants and discrimination of various phenolic substances

Several strategies, such as increasing catalytic active sites, doping another element, and designing hybrids, have been used to enhance the catalytic efficiency of the nanozyme for the efficient degradation of pollutants, sensitive analysis, and effective disease therapy. However, multifunctional nanozyme catalysts from a single MOF precursor with improved catalytic activity lack systematic research. Here, we have developed six nanozyme composites from a cobalt-based zeolitic imidazole framework (ZIF-67) as a precursor by doping metal ions (Ni2+ or Cu2+, or Fe2+) and subsequent high-temperature treatment. It is found that three kinds of metal ions-doped ZIF-67 and their corresponding high-temperature pyrolysis exhibit three kinds of catalytic activity including peroxidase-like, oxidase-like, and pollutant-reduced degradation nanozyme. Firstly, the degradation rate of pollutant substrates is increased by more than 13.3 times by doping metal ions (Ni2+ or Cu2+, or Fe2+) in ZIF-67. Moreover, a more than 96.3-fold enhancement is achieved by integrating doped-metal ions and pyrolysis of ZIF-67. Secondly, the oxidase-like activity of decorated-metal ions (Ni2+ or Cu2+, or Fe2+) ZIF-67 is enhanced by more than 300%. Thirdly, it is found that the reactive oxygen intermediate species (ROS) including singlet oxygen (1O2) and superoxide anion (•O2–) are produced by the oxidase-like reaction. Finally, we have proposed a facile and high-performance sensor array for colorimetric quantification and discrimination of nine phenolic pollutants and five biological molecules at no less than 2.0 μM by employing three decorated-metal ions ZIF-67 composite as the oxidase-like nanozyme. Ultimately, the colorimetric array sensor has great potential application prospects in monitoring environmental phenolic pollutants and disease diagnosis.