Two structural types of lanthanide MOFs based on long chain flexible sebacic acid: Syntheses, luminescence, sensing, and magnetic properties

Abstract

Five new lanthanide metal-organic frameworks (MOFs) with two different structures [Dy(Seb)1.5(H2O)2]n (H2Seb = sebacic acid, 1) and {[Ln2(Seb)3H2O]·0.5H2O}n {Ln = Sm (2a), Eu (2b), Gd (2c) and Tb (2d)} have been solvo-thermally synthesized and structurally characterized. 1 shows a 2-D sql layer, while 2a-d are isostructural and exhibit a new structural type of 3-D lanthanide sebacates constructed by the combination of long chain flexible sebacic acid ligands and rare edge-shared chains of LnO8(H2O)x (x = 0, 1) polyhedrons. Luminescent measurements indicate that europium (2b) and terbium (2d) sebacates not only show remarkable red- and green-light luminescent properties, respectively, but also serve as luminescent sensors for the quick and effective detection of Fe3+, CrO42- and Cr2O72- ions with low detection limits of 4.38 ~ 6.92 ppm. Although a few transition metal sebacates are applied for sensing Fe3+ ion, no lanthanide sebacate based sensors for the detection of Fe3+, CrO42- and Cr2O72- ions are emerged. Therefore, 2b and 2d offer an only example of the lanthanide sebacate based sensor capable of sensing Fe3+, CrO42- and Cr2O72- ions, significantly extending the potential applications of lanthanide sebacates. Moreover, magnetic investigations of 1, 2a, and 2c-d show that 1 is typical slow relaxation of the magnetization, while 2c exhibits significant magnetocaloric effect with the value of -ΔSm of 36.32 J/(kg∙K) at 2 K (ΔH = 7 T).