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.
Chao Zhang, Zixiao Liu, Zhe Gong et al.· Inorganic Chemistry· 0 citations
Gas–liquid interfacial nucleation can influence organic crystallization, yet its mechanistic role in polymorph selection remains poorly understood. Here, we demonstrate that nucleation at the gas–liquid interface of flufenamic acid solutions governs polymorph selection and gives rise to a pronounced concentration-dependent polymorphism, wherein low initial concentrations favor the nucleation of form I, higher concentrations yield form III, and intermediate concentrations selectively produce the metastable form IV. In situ synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS) directly resolves the formation and evolution of prenucleation assemblies at the interface, revealing three distinct interfacial molecular evolution pathways correlated with the emergence of specific polymorphs. Molecular dynamics (MD) simulations combined with energy calculations within the hybrid quantum mechanics/molecular mechanics (QM/MM) embedded-cluster framework further reveal interfacial enrichment, orientational bias, and conformer-dependent stabilization of stacking motifs, providing a microscopic interpretation of the experimentally observed selectivity. Together, these results establish the gas–liquid interface as an active structural selector that reshapes molecular organization prior to nucleation, offering a mechanistic framework for understanding and controlling polymorphism in evaporation-driven crystallization.
Yu Liu, Xu Zhang, Xingfan Zhang et al.· Journal of the American Chem...· 0 citations