A double-tartrate-bridged deca-nuclearity europium-tungsten cluster embedded selenotungstate and its selective optical sensing of o-nitrophenol

An inorganic–organic hybrid Eu–W-implanted tartrate-connected selenotungstate tetramer {[Eu₄(H₂O)₁₂W₆O₁₂(tar)₂][B-α-SeW₉O₃₃]₄}¹⁶⁻ (1a, H₄tar = tartaric acid) was successfully obtained by introducing the flexible multidentate tartrate ligand into the Se-templated lacunary polyoxometalate (POM) and lanthanide (Ln) system. Within 1a, two identical penta-nuclear Eu₂W₃-cluster-encapsulated dimeric units {[Eu₂(H₂O)₆W₃O₆][B-α-SeW₉O₃₃]₂}⁴⁻ are arranged in an ''open C-shaped'' configuration, interconnected by double tetra-dentate tar⁴⁻ linkers. Moreover, 1a demonstrates notable stability and intense photoluminescence (PL) emission in an aqueous environment. This emission proves effective in discriminating the toxic chemical pollutant o-nitrophenol (o-NP) from its isomers m-nitrophenol (m-NP) and p-nitrophenol (p-NP), achieving highly selective and sensitive discrimination of o-NP with a low detection limit of 0.73 μM. The practical applicability of probe 1a was demonstrated in lake water, exhibiting suitable recoveries. The PL sensing mechanism involving static quenching and competitive absorption was elucidated finally. This accomplishment sets the groundwork for the deliberate synthesis of novel organic ligands and Ln-functionalized POM hybrids. Furthermore, it propels the exploration of POM materials for the recognition of environmental pollutants.