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 (CrO42– and Cr2O72–) 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.