The synthesis of nanomaterials with specific properties and functions as biomimetic nanoenzymes has attracted extensive attention in the past decades due to their great potential to substitute natural enzymes. Herein, a facile and simple method for the preparation of platinum nanoparticle (PtNP)-decorated two-dimensional metal-organic framework (MOF) nanocomposites was developed. A ligand with heme-like structure, Fe(III) tetra(4-carboxyphenyl)porphine chloride (TCPP(Fe)), was applied to synthesize MOF nanosheets (denoted as Cu-TCPP(Fe) nanosheets) in high yield. Ultrathin Cu-TCPP(Fe) nanosheets with thickness less than 10 nm were used as a novel template for the growth of ultrasmall and uniform PtNPs. Significantly, the obtained hybrid nanomaterials (PtNPs/Cu-TCPP(Fe) hybrid nanosheets) exhibit enhanced peroxidase-like activity compared to PtNPs, Cu-TCPP(Fe) nanosheets, and the physical mixture of both due to the synergistic effect. On account of the excellent peroxidase-like activity of PtNPs/Cu-TCPP(Fe) hybrid nanosheets, we established a colorimetric method for sensitive and rapid detection of hydrogen peroxide. Furthermore, by combining with glucose oxidase, a cascade colorimetric method was established to further detect glucose with excellent sensitivity and selectivity.

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Compared with conventional bulk 3D metal-organic framework (MOF), the MOF nanosheets possess large surface area, ultrathin thickness, and well solution dispersion properties, which is suitable to be used as novel templates to synthesize the functional composites. However, up to now, it remains difficult to grow noble metal nanoplates on 2D MOF surface due to the complexity of synthetic process. Here, for the first time, we used MOF nanosheets (Cu-TCPP or Cu-TCPP(Fe)) as an template for the solution-phase growth of silver (Ag), gold (Au), and palladium (Pd) nanoplates at ambient conditions. The noble metal plates on the surface of 2D MOF are uniform and possess ultrathin structure, which are the ideal materials for catalysis due to accessible active sites, fast electron transfer, high stability, and good solution-dispersion. Notably, the synthesized Pd/Cu-TCPP(Fe) hybrid nanomaterials shows enzyme-mimic catalytic activity, which exhibits enhanced catalytic performance compared to Pd nanoplates, MOF nanosheets, and their mixture. Owing to their high catalytic activity, a simple, fast and highly sensitive fluorescence method was developed to detect explosive residues such as organic peroxides in trace amounts, which existed widely in the environment.

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