Ultrastable Lanthanide Metal-Organic Frameworks for Smartphone-Assisted Ratiometric Fluorescent Sensing of Toluenediamines and Tunable Luminescence.

Lanthanide metal-organic frameworks (Ln-MOFs) have excellent optical properties and structural diversity, providing a unique platform for the development of fluorescent sensing and optical materials. In the work described herein, a series of isostructural 3D Ln-MOFs [Ln(L)(HO)]·2HO (Ln = Eu (), Gd (), Tb (), HL = 3,3',3″-[1,3,5-benzenetriyltris(carbonylimino)]tris-benzoate) are fabricated under solvothermal conditions. The good thermal, water, and acid-base stabilities of are prerequisites for fluorescent sensing applications. can be used as a ratiometric broad-spectrum fluorescent sensor for toluenediamines (TDAs) in real urine with the advantages of visualization, ultrasensitivity, and selectivity. Interestingly, a smartphone-assisted intelligent sensing platform manifests promising results for the detection of TDAs, providing a chance for further development of portable diagnostic tools. In addition, by tuning the ratios of Eu/Tb and Eu/Gd/Tb, nine bimetallic-doped EuTb ( = 0.10-0.90, -) and one trimetallic-doped GdTbEu () were obtained. - exhibit a gradient of luminescent colors from yellow-green to pink with different ratios of Eu and Tb ions. Meanwhile, the trimetallic-doped GdTbEu () shows near-white-light emission with a quantum yield of 8.76%. Interestingly, the inks made with - are invisible under ambient light but show visual color-tunable luminescence under a 254 nm UV lamp, which may facilitate their anti-counterfeiting applications.