A novel hybrid MOF–metal oxide electrochemical sensor for ultra-trace detection of cadmium ions

Designing electrochemical sensor material with highly efficient detection ability and cost-effectiveness is challenging. Conventional electrochemical sensor materials have inherent drawbacks, including poor selectivity, limited active surface area, and sluggish electron transfer kinetics. Herein, an alternative hybrid metal organic framework (Co₃O₄-Cu-BTC (CoBCPE))-metal oxide (Co₃O₄ (CoCPE)) material via layer-by-layer assembly is developed to circumvent these shortcomings. The obtained results evidently indicate that the loading of Co₃O₄ onto the Co₃O₄-Cu-BTC hybrid material leads to an improvement in the Brunauer-Emmett-Teller (BET) specific surface area (91.02 m²/g and 205.1 m²/g) of the hybrid MOF-metal oxide. The integration of Co₃O₄ with Cu-BTC metal–organic frameworks further improves porosity, ion accessibility, and electrocatalytic performance, owing to the synergy effect. The electrochemical surface area was calculated to be 3.51 cm² and 4.61 cm² for CoCPE and CoBCPE, respectively. Various experimental conditions were optimized to maximize the sensitivity of cadmium determination employing each kind of proposed electrode. The detection limits of 0.095 mg/L and 0.069 mg/L were calculated for CoCPE (5 %) and CoBCPE (1 %), respectively, showing that modified cobalt oxides (Co₃O₄-Cu-BTC) provided better determination performance. These results indicated that the hybrid material provides a lower detection limit even at 5 % less quantity. The remarkable findings of this study highlight the exciting potential of Co₃O₄ and Co₃O₄-Cu-BTC electrochemical sensors for ultra-trace cadmium detection in real-world applications.