Microenvironment Regulation of Multivariate Metal–Organic Frameworks Facilitating the Detection of Common Oral Drugs

A series of multivariate metal–organic frameworks, MIL-125(Ti–Ni)–xNH2 (x = 0, 25%, 50%, 75%, and 100%), were achieved by introducing Ni(II) ions and an amino-functionalized ligand. The MIL-125(Ti–Ni)–xNH2 series was employed as electrochemical sensors for oral drugs, and MIL-125(Ti–Ni)–xNH2 (x = 25% and 50%) exhibited the most promising performance for metronidazole (MNZ) and acetaminophen (AP) detection, respectively. These results may be attributed to microenvironmental adjustment within the MIL-125(Ti–Ni)–xNH2 series. Under optimized conditions, the linear response ranged from 2 to 222 μM for MIL-125(Ti–Ni)–25%NH2 in the detection of MNZ with a limit of detection (LOD) of 0.072 μM (S/N = 3). At the same time, MIL-125(Ti–Ni)–50%NH2 exhibited a linear relationship with the AP concentration of 2 ∼ 508 μM, and the LOD was assessed to be 0.32 μM (S/N = 3). In addition, MIL-125(Ti–Ni)–xNH2 (x = 25% and 50%) offers a promising platform for determining MNZ or AP in real sample analysis due to its wide linear range, low detection limit, high selectivity, and excellent stability.