Metal-Organic Framework (MOF)-Based Sensors for Mercury (Hg) Detection: Design Strategies and Recent Progress

Monitoring mercury (Hg) is critical for environmental and public health. Metal-organic framework (MOF)-based sensors demonstrate the advantage of high sensitivity and rapid response. We summarize the advances of MOF sensors for Hg detection from the perspective of MOF type and role in the sensors. First, we introduce three MOFs used in Hg sensors-UIO, ZIF, and MIL-that have demonstrated superior performance. Then, we discuss the specifics of MOF-based sensors for Hg detection in terms of the recognition and signal elements. Currently, the recognition elements include T-rich aptamers, noble metal nanoparticles, central metal ions, and organic functional groups inherent to MOFs. Sensors with fluorescence and colorimetric signals are the two main types of optical MOF sensors used for Hg detection. Electrochemical sensors have also been fabricated, but these are less frequently reported, potentially due to the limited conductivity and cycling stability of MOFs. Notably, dual-signal sensors mitigate background signals interference and enhance the accuracy of Hg detection. Furthermore, to facilitate portability and user-friendliness, portable devices such as microfluidics, paper-based devices, and smartphones have been developed for Hg detection, showcasing potential applications. We also address the challenges related to MOF-based sensors for Hg and future outlook.