Two luminescent lanthanide coordination polymers incorporating free pyridyl sites as the multi-responsive sensors for hazardous ions

The fast and effective detection of hazardous ions is very necessary owing to their serious effects on the ecological environment and human health. In this work, π-conjugated 1,10-phenanthroline (phen) chromophore has been utilized in combination with 2,2′-bipyridine-3,3′-dicarboxylate (H 2 bpdc) as a double-pyridyl-functionalized spacer to create two luminescent lanthanide coordination polymers [Ln 2 (phen) 2 (bpdc) 3 (H 2 O) 2 ] n ·6nH 2 O {Ln = Eu ( 1 ) and Tb ( 2 )}, which were characterized by elemental analysis , thermogravimetric analyses, PXRD , single-crystal X-ray diffraction, IR and UV/Vis spectroscopy. 1 and 2 consist of free H 2 O molecules and 1-D polymeric chains [Ln 2 (phen) 2 (bpdc) 3 (H 2 O) 2 ] n constructed by the linkages of [Ln(phen)(H 2 O)] 3+ groups and bpdc 2− ligands. Owing to the existence of free Lewis basic pyridyl sites as the receptor, 1 and 2 exhibit fast response (approximate 20–50 s) and high efficiency for detecting various hazardous ions (Pb 2+ , Fe 3+ , Co 2+ , Cu 2+ , Al 3+ , CrO 4 2− and Cr 2 O 7 2− ) in aqueous solution, which have the higher Ksv values of 1.80 × 10 4 –9.78 × 10 4 M −1 and the lower detection limits of 0.939–6.826 ppm. Intriguingly, most of the reported luminescent lanthanide coordination polymers can be served as either separate- or dual-responsive sensors for the detection of hazardous ions to date, however, reports on the multi-responsive sensors of a multiplicity of hazardous ions in aqueous media are relatively scarce. Therefore, 1 and 2 can be regarded as a new type of the multi-responsive sensor for fast and effectively detecting a variety of hazardous ions in water. The free pyridyl sites of 1-D europium coordination polymeric framework as the receptor can fast and effectively recognize a multiplicity of hazardous ions (Pb 2+ , Fe 3+ , Co 2+ , Cu 2+ , Al 3+ , CrO 4 2− and Cr 2 O 7 2− ). • Two luminescent lanthanide coordination polymers were prepared. • 1 and 2 can act as the multi-responsive sensors for various hazardous ions. • 1 shows characteristic Eu 3+ emission with the higher quantum efficiency of 56.2%.