Ultra‐High‐Brightness Lanthanide Organic Framework X‐Ray Scintillators: Gadolinium Salt Purity Monitoring and Photoresponsive Trifluoroacetic Acid Vapor

In this work, uncoordinated ‐OH active sites were introduced into the classical aggregation‐induced emission luminogens (AIEgen) core to construct a lanthanide metal‐organic framework (Ln‐MOFs)‐based ultra‐high‐brightness X‐ray scintillator with highly sensitive smart photoresponse TFA vapor performance, and gadolinium salt purity monitoring was expanded. Based on the coordination‐induced emission (CIE) effect and the rigidity of the MOF framework, the large amount of aggregated AIEgen in the Tb‐MOF structure efficiently promotes the antenna effect and significantly enhances the characteristic luminescence of Tb(III) ions. Therefore, the Tb‐MOF‐based X‐ray scintillator exhibited a high light yield of 37 145 photons·MeV −1 , a detection limit of 339 nGy/s (16.3 times lower than the clinical standard of 5.5 µGy s −1 ), and excellent radiation stability, achieving ultra‐high‐definition X‐ray imaging. The optimal energy level matching between the AIEgen ligand and the Eu(III) ion, Gd 0.99 Eu 0.01 ‐MOF with a Eu(III) ion content of only 1%, exhibited very bright Eu(III) ion characteristic red luminescence (slope K is as high as 32 142), enabling efficient detection of trace Eu(III) impurities in commercially available Gd(III) salts from different manufacturers. Furthermore, the abundant ‐OH groups within the pores provide active sites, resulting in both Tb‐MOF and Eu‐MOF exhibiting rapid, convenient, and highly sensitive intelligent photoresponse behavior to highly toxic TFA vapor.