Development of MOF-derived Co 3 O 4 microspheres composed of fiber stacks for simultaneous electrochemical detection of Pb 2+ and Cu 2 .

As an ideal transition metal oxide, Co 3 O 4 is a P-type semiconductor with excellent electrical conductivity, non-toxicity and low cost. This work reports the successful construction of Co 3 O 4 materials derived from metal-organic frameworks (MOFs) using a surfactant micelle template-solvothermal method. The modified electrodes are investigated for their ability to electrochemically detect Pb 2+ and Cu 2+ in aqueous environments. By adjusting the mass ratios of alkaline modifiers, the morphological microstructures of Co 3 O 4 -X exhibit a transition from distinctive microspheres composed of fiber stacks to rods. The results indicate that Co 3 O 4 -1(NH 4 F/CO(NH 2 ) 2  = 1:0) has a distinctive microsphere structure composed of stacked fibers, unlike the other two materials. Co 3 O 4 -1/GCE is used as the active material of the modified electrode, it shows the largest peak response currents to Pb 2+ and Cu 2+ , and efficiently detects Pb 2+ and Cu 2+ in the aqueous environment individually and simultaneously. The linear response range of Co 3 O 4 -1/GCE for the simultaneous detection of Pb 2+ and Cu 2+ is 0.5-1.5 μM, with the limits of detection (LOD, S/N = 3) are 9.77 nM and 14.97 nM, respectively. The material exhibits a favorable electrochemical response, via a distinctive Co 3 O 4 -1 microsphere structure composed of stacked fibers. This structure enhances the number of active adsorption sites on the material, thereby facilitating the adsorption of heavy metal ions (HMIs). The presence of oxygen vacancies (O V ) can also facilitate the adsorption of ions. The Co 3 O 4 -1/GCE electrode also exhibits excellent anti-interference ability, stability, and repeatability. This is of great practical significance for detecting Pb 2+ and Cu 2+ in real water samples and provides a new approach for developing high-performance metal oxide electrochemical sensors derived from MOFs.