Coordination-Defect-Driven Construction of Responsive Pure-MOF Microspheres for Switchable Mode-Dependent Anticounterfeiting Labels.

Luminescent metal-organic frameworks (MOFs) with exceptional dynamics and diverse active sites possess tremendous potential in information security and anticounterfeiting applications. However, traditional MOF systems are based on broadband spectral signals with spectrum overlap, which easily leads to low-resolution signal identification, compromising the overall security level. Here, we report the coordination-defect-induced amorphous pure-MOF microsphere with switchable whispering-gallery-mode (WGM) signals as a mode-dependent security platform. Amorphous MOF microspheres are prepared by a chlorine coordination-defect-driven growth strategy based on the aperiodic arrangement in coordinate networks. The as-prepared amorphous MOF microspheres with well-defined circular morphology display the typical WGM resonance with dimension-dependent character, permitting the creation of photonic barcodes with substantial encoding capacity. Furthermore, the amorphous MOF microspheres exhibit optical mode switching behavior due to reversible framework shrinkage, which enables the design of covert photonic barcodes as anticounterfeiting labels, finally demonstrating responsive coding property and enhanced information security. The results provide a novel strategy for exploring an MOF-based security platform for information encryption and optical anticounterfeiting.