Enhanced Ni2+/Ni3+ redox activity in dopant-free nickel-based metal–organic framework for sensitive electrochemical detection of methanol in beverages

Abstract

This work presents a dopant-free nickel-based metal–organic framework (Ni-MOF) electrode revealing enhanced Ni²⁺/Ni³⁺ redox action for the sensitive electrochemical detection of methanol at room temperature. The scientific interest in volatile organic compounds (VOCs) detection has been significant because of its relevance in the prevention of adulteration-related intoxication. The differences in VOC levels in the human body are valuable predictors of underlying pathophysiological processes and are linked to the identification and monitoring of numerous diseases. A dopant-free Ni-MOF was synthesized in the current study, and its structural and morphological properties were thoroughly characterized with X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FESEM), High-resolution Transmission electron microscopy (HRTEM), and X-ray Photoelectron Spectroscopy (XPS). The electrochemical properties of the synthesised Ni-MOF material were investigated using a glassy carbon electrode as the working electrode. The VOC sensor based on the Ni-MOF material revealed a high analytical performance with a low LOD of 0.5 µM and a high sensitivity of 144.22 µA µM⁻¹ cm⁻² with a linear range from 0.5 to 11 µM. These findings illustrate that the Ni-MOF material would be a viable electrochemical sensing platform for VOCs. The sensor allows indirect detection of methanol in real samples, such as natural and artificial beverages. The recoveries were 95–107% with spiked sample analysis, which showed excellent analytical reliability and a low degree of matrix effects. In general, the proposed work demonstrates the possibilities of applied methanol monitoring in food and drink safety sectors, supporting human health protection.