Near-Unity Energy Transfer from Uranyl to Europium in a Heterobimetallic Organic Framework with Record-Breaking Quantum Yield
Yugang Zhang, Xia Wang, Kexin Xu, Fuwan Zhai, Jie Shu, Ye Tao, Junren Wang, Lisha Jiang, Liangwei Yang, Yaxing Wang, Wei Liu, Jing Su, Zhifang Chai, Shuao Wang
Abstract
Lanthanide organic frameworks (Ln-MOFs) have attracted increasing research enthusiasm as photoluminescent materials. However, limited luminescence efficiency stemming from restricted energy transfer efficiency from the organic linker to the metal center hinders their applications. Herein, a uranyl sensitization approach was proposed to boost the luminescence efficiency of 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 determined to benefit from nearly 100% energy transfer efficiency between UO 2 2+ and Eu 3+ . Time-dependent density functional theory and ab initio wave-function theory calculations confirmed the overlap of excited state levels between UO 2 2+ and Eu 3+, which is responsible for the efficient energy transfer process. Coupled with intrinsically strong stopping power toward X-ray of the uranium center, SCU-UEu-2 features an ultralow detection limit of 1.243 μGyair/s, outperforming the commercial scintillator LYSO (13.257 μGyair/s) and satisfying the requirement of X-ray diagnosis (below 5.5 μGyair/s) in full.