Near-Unity Energy Transfer from Uranyl to Europium in a Heterobimetallic Organic Framework with Record-Breaking Quantum Yield

Lanthanideorganic frameworks (Ln-MOFs) have attracted increasingresearch enthusiasm as photoluminescent materials. However, limitedluminescence efficiency stemming from restricted energy transfer efficiencyfrom the organic linker to the metal center hinders their applications.Herein, a uranyl sensitization approach was proposed to boost theluminescence efficiency of Ln-MOFs in a distinct heterobimetallicuranyl-europium organic framework. The record-breaking photoluminescencequantum yield (PLQY, 92.68%) among all reported Eu-MOFs was determinedto benefit from nearly 100% energy transfer efficiency between UO2 (2+) and Eu3+. Time-dependent densityfunctional theory and ab initio wave-function theory calculationsconfirmed the overlap of excited state levels between UO2 (2+) and Eu3+, which is responsible for the efficientenergy transfer process. Coupled with intrinsically strong stoppingpower toward X-ray of the uranium center, SCU-UEu-2 features an ultralowdetection limit of 1.243 mu Gyair/s, outperforming the commercialscintillator LYSO (13.257 mu Gyair/s) and satisfying the requirementof X-ray diagnosis (below 5.5 mu Gyair/s) in full.

Automated summary

In this study, a uranyl sensitization approach was proposed to enhance the luminescence efficiency of lanthanide organic frameworks (Ln-MOFs) in a distinct heterobimetallic uranyl-europium organic framework. The record-breaking photoluminescence quantum yield (PLQY, 92.68%) among all reported Eu-MOFs was achieved by nearly 100% energy transfer efficiency between UO2 (2+) and Eu3+. The overlap of excited state levels between UO2 (2+) and Eu3+ was confirmed to be responsible for the efficient energy transfer process.