Coordination-Defect-Driven\nConstruction of Responsive\nPure-MOF Microspheres for Switchable Mode-Dependent Anticounterfeiting\nLabels

Luminescent metal–organic frameworks (MOFs) with\nexceptional\ndynamics and diverse active sites possess tremendous potential in\ninformation security and anticounterfeiting applications. However,\ntraditional MOF systems are based on broadband spectral signals with\nspectrum overlap, which easily leads to low-resolution signal identification,\ncompromising the overall security level. Here, we report the coordination-defect-induced\namorphous pure-MOF microsphere with switchable whispering-gallery-mode\n(WGM) signals as a mode-dependent security platform. Amorphous MOF\nmicrospheres are prepared by a chlorine coordination-defect-driven\ngrowth strategy based on the aperiodic arrangement in coordinate networks.\nThe as-prepared amorphous MOF microspheres with well-defined circular\nmorphology display the typical WGM resonance with dimension-dependent\ncharacter, permitting the creation of photonic barcodes with substantial\nencoding capacity. Furthermore, the amorphous MOF microspheres exhibit\noptical mode switching behavior due to reversible framework shrinkage,\nwhich enables the design of covert photonic barcodes as anticounterfeiting\nlabels, finally demonstrating responsive coding property and enhanced\ninformation security. The results provide a novel strategy for exploring\nan MOF-based security platform for information encryption and optical\nanticounterfeiting.