Multivariate metal-organic frameworks facilitating electrochemical detection of small biomolecules and...

Early identification of abnormal levels of uric acid (UA), xanthine (XA), and hypoxanthine (HXA) in body fluids and food could assist in the prevention of various diseases. Additionally, one of the antibiotics, chloramphenicol (CAP), when used excessively, can cause harmful side effects on human/animal health and ecological risks. Therefore, the accurate detection of these substances is of great significance. Herein, the V(IV) species and amino-functionalized terephthalic acid were selected to prepare a series of multivariate heterometallic-organic frameworks, MIL-125(Ti-V)-xNH₂ (x = 0, 25%, 50%, 75%, and 100%), which was established as an electrochemical sensing platform for detecting small organic molecules. Integrating electrocatalytically active vanadium centers and polar amino groups within the cavity of parent MIL-125(Ti) regulates the electrocatalytic activity and selectivity toward electrochemical detection. Under optimal conditions, MIL-125(Ti-V)-100%NH₂ exhibited a linear detection range of 2 to 150 µM for simultaneous detection of UA, XA, and HXA with detection limits of 0.520, 0.502 and 0.620 μM (S/N = 3), respectively. In addition, MIL-125(Ti-V)-100%NH₂ exhibited the best performance for CAP detection with an outstanding wide linear response range (1 to 310 µM) and a low limit of detection (0.0020 μM, S/N = 3). Owing to the wide linear range, low detection limit, high selectivity, and excellent stability, MIL-125(Ti-V)-100%NH₂ provided an ideal platform for real sample analyses.