A simple approach to fabricate a highly-sensitive lead( <scp>ii</scp> ) ion electrochemical sensor based on plate-shaped Cu-BTC and particle-shaped Fe-BTC

A challenging task is to study and improve the electrochemical behaviors and sensing performance of Fe-BTC and Cu-BTC-based electrodes for sensitive detection toward lead(ii) ions (Pb²⁺). In the present work, particle-shaped Fe-BTC was effectively decorated on the plate-like Cu-BTC substrate to form a 3D-composite architecture using the microwave-assisted electrochemical method and successfully detected Pb²⁺ ions for the first time. This hierarchical structure served as a promising candidate for modifying the working electrode surface, facilitating favorably the electrochemical reaction of Pb²⁺ ions. The structural and morphological characteristics were thoroughly investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD), confirming the successful integration of Fe-BTC and Cu-BTC phases. Interestingly, the Fe-BTC@Cu-BTC-modified screen-printed electrode (SPE) exhibited several advantageous features, including enhanced electrical conductivity, increased electroactive surface area, and superior electron transfer kinetics. Consequently, the Fe-BTC@Cu-BTC/SPE demonstrated a low overpotential for Pb²⁺ oxidation, a wide linear detection range, low limit of detection (LOD), high sensitivity, and excellent selectivity. Its practical applicability was further validated through successful Pb²⁺ detection in shampoo samples. Besides, this study provided useful insights into the nature of the enhancement from effective integration between geometric configuration and compositional integration of Fe-BTC and Cu-BTC materials to guide the design of suitable metal-organic framework (MOF) structures for high-performance electrochemical sensing and related applications.