Ferrocene-functionalized Ni(II)-based metal-organic framework as electrochemical sensing interface for ratiometric analysis of Cu2+, Pb2+ and Cd2+

The development of selective electrochemical response materials and new detection strategies are the research focus in the field of heavy metal ion (HMI) electroanalysis. Herein, a Ni(II)-based metal-organic framework (NH2-Ni-MOF) was synthesized and functionalized by electrochemically active molecule of ferrocene (Fc) via post-synthesis modification. Based on the Fc-functionalized NH2-Ni-MOF (Fc-NH2-Ni-MOF), a novel electrochemical ratiometric sensing platform was developed and applied for the simultaneous determination of various HMIs. The prepared NH2-Ni-MOF exhibits nanoplate structure, which is conducive to increase accessible electrode area and expose more active sites, thus promoting the adsorption and pre-concentration of HMIs. The modification of Fc on MOF not only enhances the electrical conductivity of the MOF material, but also provides an internal reference signal for the ratiometric analysis. Due to the excellent characteristics of the Fc-NH2-NiMOF, the as-prepared ratiometric electrochemical sensing platform exhibits wide linear ranges (0.001 mu M to 2.0 mu M for lead ions (Pb2+), and 0.01 mu M to 2.0 mu M for copper ions (Cu2+) as well as cadmium ions (Cd2+)) and high sensitivity (the detection limit toward Cu2+, Pb2+ and Cd2+ is 6.3 nM, 0.2 nM and 7.1 nM, respectively). In addition, compared with the non-ratiometric strategy, the reproducibility of ratiometric analysis is significantly improved. The developed electrochemical method with high sensitivity, selectivity and reliability exhibits bright application prospects in the detection of real samples. Moreover, the electrochemical application of MOF materials has been effectively expanded.

Automated summary

The development of selective electrochemical response materials and new detection strategies for heavy metal ions (HMI) electroanalysis is of research interest. A Ni(II)-based metal-organic framework (NH2-Ni-MOF) was synthesized and functionalized with the electrochemically active molecule ferrocene (Fc), leading to the development of a novel electrochemical ratiometric sensing platform. This platform demonstrates wide linear ranges, high sensitivity, and improved reproducibility compared to non-ratiometric strategies. The modification of Fc on MOF enhances material conductivity and provides an internal reference for ratiometric analysis.