Disproportionation Thermochromic Response in a Luminescent Lanthanide Metal-Organic Framework

Stimuli-responsive luminescent materials are highly attractive as smart materials for advanced photonic applications. However, most luminescent materials typically display monotonous responses to external stimuli, posing limitations for applications such as information security. This work presents a class of luminescent lanthanide metal-organic frameworks (Ln-MOFs) that display disproportionation responses to thermal stimuli by appropriate doping. The lanthanide-benzenetricarboxylate (Ln-BTC) MOFs undergo a phase transition due to the loss of coordinated water as the temperature increases. The phase transition shortens the interionic distance, thereby promoting Tb³⁺-to-Eu³⁺ energy transfer in Tb/Eu-BTCs and turning the emission color from yellow to orange. Intriguingly, further doping of Yb³⁺ in the mixed Ln-MOFs can block the energy transfer from Tb³⁺ to Eu³⁺ and simultaneously quench the luminescence of Eu³⁺ after the phase transition, reversing the color change from yellow to green. The deliberately designable thermochromic responses offer promising opportunities for information encryption.

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