In Situ Ligand Formation-Driven Synthesis of a Uranyl Organic Framework as a Turn-on Fluorescent pH Sensor

A uranium-based metal–organic framework, [(UO 2 )(H 2 DTATC)] ( HNU-39, H 4 DTATC = 5,5′-(9,10-dihydroxy-4a,9,9a,10-tetrahydroanthracene-9,10-diyl)diisophthalic acid) was successfully prepared by a hydrothermal method. The structure of HNU-39 comprises UO 8 hexagonal bipyramids linked by doubly protonated DTATC ligands, forming a ribbon arrangement. It is worth noting that the DTATC ligand was transformed in situ from 5,5′-(anthracene-9,10-diyl)diisophthalic acid (H 4 DPATC) during the synthesis of HNU-39 . Research on fluorescence properties has shown that HNU-39 exhibits fluorescence turn-on response under alkaline conditions and could be used as a potential pH sensor. Moreover, HNU-39 can also be successfully applied for pH sensing in real samples from a sewage treatment plant. The sensing mechanism can be interpreted as OH – ions reacting with the protons in the organic ligand of HNU-39 .