Covert MOF-Based Photoluminescent Tags via Tunable Linker Energetics

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Optical anticounterfeiting tags require complex optical properties and ease of production.
• Metal-organic frameworks (MOFs) offer tunable structures and energy transfer for advanced materials.
• Rare earth clusters within MOFs provide unique photoluminescent properties.

Purpose of the Study:

• To design and synthesize novel heterometallic MOFs for optical anticounterfeiting applications.
• To create optical tags with concealed visible emissions and covert infrared signals.
• To explore the impact of linker selection on MOF photoluminescent properties.

Main Methods:

• Synthesis of heterometallic MOFs using combinations of Eu, Nd, and Yb with a tetratopic linker.
• Characterization of MOF structure, including the identification of novel 11-metal clusters.
• Analysis of photoluminescent properties, including emission spectra and decay dynamics.

Main Results:

• Developed MOFs that conceal visible europium emissions while retaining near-infrared emissions from neodymium and ytterbium.
• Discovered a novel 11-metal cluster in Yb-containing MOFs, alongside a common 9-metal cluster.
• Demonstrated the utility of these MOFs as optical tags with orthogonal identifiers for authentication.

Conclusions:

• Linker selection critically influences photoluminescent properties in MOFs.
• The synthesized MOFs serve as effective optical tags with multiple covert authentication elements.
• This work opens new possibilities for designing complex, multifunctional optical materials.