An Acid-Resistant Lanthanide Metal–Organic Framework Based on Tetraphenylethylene as an Electrochemical Nitrite Sensor

Nitrite (NO₂^-) is attracting increasing attention due to its harmful effect on human health. Thus, it is highly desirable to construct effective electrochemical sensors to detect the presence of NO₂^-. The majority of electrochemical NO₂^- detection is focused on alkaline or neutral electrolyte solutions and is rarely reported under acidic conditions. In this work, a tetraphenylethylene (TPE)-based 2D lanthanide metal-organic framework (Ln-MOF), (Me₂NH₂)[Ho^III(tcbpe-F)DMF]•DMF•H₂O (1) (tcbpe-F = 4',4‴,4″‴,4″″‴-(ethene-1,1,2,2-tetrayl)tetrakis(3-fluoro-[1,1'-biphenyl]-4-carboxylic acid, DMF = N,N-dimethylformamide)), has been successfully fabricated on carbon paper (CP) by an in situ hydrothermal method. As a NO₂^- sensor, the fabricated 1 electrode exhibited excellent electrochemical performance in the H₂SO₄ electrolyte (pH = 1) and offers high sensitivities of 1453.2 and 591.5 μA mM^-1 cm^-2, with a wide linear detection range of 0.1 μM to 9 M, a low detection limit of 60 nM, excellent specificity even in the presence of various analytes (metal ions, anions, and organic molecules) and real water samples, satisfactory stability, and reproducibility. This is the first report of TPE-based Ln-MOF as a NO₂^- sensor, and furthermore, a plausible sensing mechanism is confirmed by experiments and theoretical computations.