Design of Rb-Based MOF: for Dual Photothermal Regulation of Multicolor Transformation and Sensitive Detection of Urinary Tract Infection Drugs

For visual anticounterfeiting and drug sensing, a novel rubidium-based organic framework material (named Rb-CMNDI) has been synthesized. Using N, N'-bis(carboxymethyl)-1,4,5,8-naphthalenedicarboximide (H2CMNDI) as the organic linker, a thermally stable metal-organic framework (MOF) with photothermal stimulus response properties was successfully constructed. Upon UV irradiation, Rb-CMNDI darkens, then turns red upon heating. Combined DFT calculations and experimental studies reveal that UV irradiation generates NDI* radical, subsequent thermal activation drives their assembly into π-stacked dimers, narrowing the bandgap from 2.72 to 1.27 eV and resulting in the emergence of a red phase and this finding uncovers a photothermal cooperative radical to dimer transformation mechanism. This unique color evolution behavior was further applied to the collaborative construction of anticounterfeiting labels with transition metal MOF, achieving visual and multilevel anticounterfeiting functions. Additionally, this MOF can also be used as a highly sensitive fluorescent sensor for the detection of the urinary tract infection nitrofurantoin, with a limit of detection (LOD) of 0.36 μM while maintaining good specificity. This work provides a novel strategy for designing alkali-metal MOFs with photothermal responsive properties, promising for intelligent encryption and antibiotic residue monitoring.