Polyoxometalate-Incorporated Metal-Organic Frameworks for Electrochemical Sensing of Dihydroxybenzene Isomers

Dihydroxybenzene isomers are highly toxic and resistant to natural degradation and pose a serious threat to the ecological environment. Therefore, developing efficient and accurate detection methods is crucial for preventing and controlling their environmental risks. A series of polyoxometalate-incorporated bimetallic metal-organic frameworks, MIL-101(CrxAl)-POM-T (x = 1.6 or 2, POM = SiW12 or PW12, T =180 or 220), were synthesized via a hydrothermal method. They were employed as electrochemical sensors determining dihydroxybenzene isomers (including hydroquinone (HQ), catechol (CC), and resorcinol (RS)). By introducing different ratios of chromium(III) to aluminum(III) centers and POM types within MIL-101(CrxAl)-POM-T, the current responses and selectivity toward different dihydroxybenzene isomers were judiciously optimized. Among them, MIL-101(Cr1.6Al)-PW12-220 exhibited the optimal electrochemical behavior with wide linear response ranges (2-120, 2-100, and 20-260 μM) and low limits of detection (0.102, 0.225, and 4.615 μM, S/N = 3) for the individual detection of HQ, CC, and RS. In addition, the excellent selectivity, reproducibility, and stability endow MIL-101(Cr1.6Al)-PW12-220 with great potential to detect dihydroxybenzene isomers in real water samples.