Synergistic Hybridization of Hf-MOF and Ce-MOF Cubic Clusters for Dual Electrochemical Detection of Nitrate and Nitrite in Tap Water

Increasing the presence of nitrate (NO 3 – ) and nitrite (NO 2 – ) in drinking water causes serious environmental and health risks, imposing reliable, quick, and sensitive detection strategies. Electrochemical sensors are promising alternatives to traditional methods, but their performance is largely limited by the electro catalytic material’s conductivity, stability, and multifunctionality. It is still challenging to develop multifunctional and compositionally integrated materials tailored for dual-ion electrochemical detection in real water samples, which remains limited despite progress in metal–organic framework (MOF)-based hybrids. This work develops a multifunctional hafnium–metal organic framework/cerium–metal organic framework (Hf-MOF/Ce-MOF) hybrid through a two-step solvothermal synthesis, integrating both MOF functionalities in a single composite system. In order to confirm crystallinity and uniform nanocluster morphology, various characterization techniques are used such as XRD and TEM, indicating successful structural integration. In addition, XPS results provide insight into the elemental composition and oxidation states, confirming the successful incorporation of the Ce-MOF into the Hf-MOF matrix within the hybrid system. The synthesized Hf-MOF/Ce-MOF is drop-cast onto a conductive copper foam (CF) substrate to fabricate the sensing interface. The fabricated sensor exhibits efficient electrochemical performance toward the detection of both NO 3 – and NO 2 – using differential pulse voltammetry (DPV). The sensor offers wide linear ranges (1–1000 μM), high sensitivity (2.4 μA/μM for NO 3 – and 2.9 μA/μM for NO 2 – ), and low detection limits (6.7 μM (NO 3 – ) and 5.04 μM (NO 2 – )). Reproducibility is confirmed with four independently prepared electrodes, and the operational stability lasts for 7 days. The CF substrate combined with redox-active Hf and Ce centers improves charge transport, catalytic activity, and ion accessibility. Nanostructured cubic clusters in this hybrid material function as a strong and sensitive sensing interface for the detection of nitrate and nitrite in untreated tap water. In addition, it holds a great potential for developing multianalyte environmental sensors for monitoring water quality.