Interaction of Congo Red with MOFs Facilitates Specific Detection of Cr(VI) in Water

In this work, three novel three-dimensional metal-organic frameworks (MOF-1-3) were successfully synthesized, and their chemical stability and intrinsic fluorescence sensing capabilities were confirmed. Property modification of MOF-1-3 was realized via the loading of Congo red (CR), a cationic dye; meanwhile, the CR loading behavior and underlying mechanism of these MOFs were systematically investigated. After CR loading, the fluorescence properties of the resulting CR@MOF-1-3 composites underwent significant changes. Notably, compared with MOF-1-3, CR@MOF-1-3 exhibited selective recognition toward Cr(VI) anions (CrO₄^2- and Cr₂O₇^2-) while effectively eliminating interference from Fe(III) ions. This study underscores the potential of CR@MOF-1-3 as multifunctional fluorescent sensing platforms for environmental monitoring and chemical analysis and provides rational guidance for the design of MOF-based fluorescent probes.