Penguin with bow tie-like bimetallic metal organic framework as colorimetric biosensing for H2O2 and L-cysteine

A penguin with bow tie-like bimetallic metal-organic framework, Cu3(MoO4)(TZ)2(OH)2 (Cu/Mo-MOF) {TZ = tetrazole}, was designed and fabricated by hydrothermal reaction of (NH4)6Mo7O24, Cu(NO3)2, NH4VO3 and 1H-tetrazole (HTZ). Single crystal X-ray diffraction shows the basic building unit of Cu/Mo-MOF is a “penguin shape” [6 + 6] metallocycles, which are further extended into a two-dimensional layer by “end-to-end” along the y-axis and an inverted “side by side” along the z-axis. It is interesting that the MoO42- anion looks like a bow tie that ties on the metallocycle improving structure stability. The bimetallic Cu/Mo-MOF was employed to detect H2O2 and L-Cys as a nanoenzyme; results from the peroxidase-like activity assay indicate the Cu/Mo-MOF possesses intrinsic peroxidase-like activity. Meanwhile, to enhance the sensor performance of Cu/Mo-MOF, the Cu/Mo-MOF/PPy nanocomposite was prepared by a chemical oxidation polymerization process of Py. Benefiting from the more active sites and the electrode/electrolyte interface, and the better electron diffusion and transport of Cu/Mo-MOF and PPy, the peroxidase-mimicking activity of the bimetallic Cu/Mo-MOF/PPy nanocomposite indeed can be greatly improved for the H2O2 and L-cysteine (L-Cys) detection, and the Cu/Mo-MOF/PPy nanocomposite exhibits a lower limit of detection (0.158 μM) among reported materials to date.