Highly pH-Responsive Sensor Based on a EuIII Metal–Organic Framework with Efficient Recognition of Arginine and Lysine in Living Cells

A lanthanide-based three-dimensional metal–organic framework with excellent water, acid/base, and solvent stability, namely {[(CH 3 ) 2 NH 2 ] 0.7 [Eu 2 (BTDBA) 1.5 (lac) 0.7 (H 2 O) 2 ]·2H 2 O·2DMF·2CH 3 CN} n ( JXUST-29, H 4 BTDBA = 4′,4‴-(benzo[ c ][1,2,5]thiadiazole-4,7-diyl)bis([1,1′-biphenyl]-3,5-dicarboxylic acid), Hlac = lactic acid), has been synthesized and characterized. Since the N atoms of the thiadiazole group will not coordinate with lanthanide ions, JXUST-29 has a free basic N-site accessible to small H + ions, which allows it to be used as a promising pH fluorescence sensor. Interestingly, the luminescence signal was significantly enhanced, with an approximately 54-fold enhancement in the emission intensity when the pH value was increased from 2 to 5, which is the typical behavior of pH probes. In addition, JXUST-29 can also be used as a luminescence sensor to detect l -arginine (Arg) and l -lysine (Lys) in an aqueous solution through fluorescence enhancement and the blue-shift effect. The detection limits were 0.023 and 0.077 μM, respectively. In addition, JXUST-29 -based devices were designed and developed to facilitate detection. Importantly, JXUST-29 is also capable of detecting and sensing Arg and Lys in living cells.