An unprecedented mixed-coordination-mode ligand based MOF with unique topology as a multi-responsive fluorescent sensor for highly sensitive detection of nitrobenzene, Fe3+, and Cr2O72−

In this study, we selected the zwitterionic flexible carboxylate ligand 1,1′,1″-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene))tris(pyridine-1-ium-4-carboxylate) (H 3 L Br 3 ) to successfully construct a novel metal-organic framework [Eu 2 L 4 (H 2 O) 4 ]·6Br 17.5H 2 O (Eu-MOF) with a novel {4^2.6}{4^3.6.8^4.10^2}{4} topology. Remarkably, this material represents the first reported MOF to successfully accommodate both tridentate and bidentate coordination modes of ligand L, breaking through the conventional limitation of monomodal coordination observed in previous systems. Fluorescence sensing experiments demonstrate that the Eu-MOF exhibits outstanding sensing performance toward nitrobenzene (NB), Fe 3+ , and Cr 2 O 7 2− , showing excellent selectivity, high sensitivity, superior selectivity capability, and good recyclability, which enables its application as a multifunctional luminescent sensor for simultaneous detection of these three analytes. This study holds significant guiding importance for the future synthesis of innovative complexes based on such ligands and their applications in the field of fluorescence sensing.