In this work, a conductive electrochemical sensor, UiO-66-NH₂@PANI, was successfully prepared by polymerizing the conductive polyaniline (PANI) polymer around the metal–organic framework UiO-66-NH₂. Fourier transform infrared spectra, X-ray diffraction patterns, and X-ray photoelectron spectral data support the formation of UiO-66-NH₂@PANI. Additionally, scanning and transmission electron microscopy investigations confirm that PANI uniformly coated the surface of UiO-66-NH₂. The resultant material was applied to construct a novel electrochemical sensor for the reliable detection of cadmium ions due to the chelation mechanism between metal cations and amine groups. Under optimized conditions, a linear detection of Cd²⁺ concentration range of 0.5–600 μg L⁻¹ was repeatable with a 0.3 μg L⁻¹ lowest level detection limit. Little to no interference effects from other co-existing ions allow the sensor to work in varying environments for practical application. This method of coating metal–organic frameworks may show utility for constructing highly sensitive electrochemical sensors for the detection of heavy metal ions and more.

The MOF, Cu₃(BTC)₂functionalized with sulfonic acidviasequential post-synthetic modification and oxidation demonstrates high cadmium uptake capacity and fast kinetics for adsorbing cadmium ions from aqueous solution.