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Two new three-dimensional (3D) Ni(II) coordination polymers (CPs), namely, {[Ni(L1)2(H2O)2]·(1,5-NDS)}n (1) and [Ni(L2)2(1,5-NDS)]n (2) have been hydrothermally synthesized based on 1,5-naphthalenedisulfonate (1,5-NDS) and two bis(benzimidazole) ligands (L1 = 1,4-bis(1H-benzimidazol-1-yl)butane, L2 = 1,2-bis(benzimidazol-1-ylmethyl)benzene). CP 1 presents a 3D framework with 4-connected 66dia topology. While CP 2 shows a 3D network with 6-connected (412.63) pcu topology. CPs 1 and 2 both exhibit excellent luminescent properties and good water stability. And luminescent sensing experiments reveal that both CPs can detect uric acid (UA) in aqueous solution through the luminescent quenching effect, and they also can detect tryptophan (Trp) in aqueous solution with red-shift and turn-on luminescent effect. The detection limits toward UA and Trp are 1.30 and 0.92 μM for 1, and those are 1.20 and 1.30 μM for 2, respectively. Furthermore, the luminescence sensing mechanisms were studied via PXRD patterns, UV–Vis spectra, lifetimes and theoretical calculations. The luminescence test films of 1 and 2 were also prepared for visual detection of UA and Trp. [ABSTRACT FROM AUTHOR]

Two Cd(II) MOFs based on the 1,4-bis[(2-methyl-1H-imidazol-1-yl)-methyl]benzene (1,4-mbix) and succinate (Suc2−) or azelate (Aze2−) ligands have been hydrothermally synthesized, namely, {[Cd2(Suc)2(1,4-mbix)2]·5H2O}n (1) and [Cd(Aze)(1,4-mbix)]n (2). Both MOFs were structurally characterized by single-crystal X-ray diffraction. In MOF 1, the Cd(II) centers are connected by Suc2− and 1,4-mbix to generate a two-dimensional (2D) sql layer with (H2O)5 water cluster. Each 2D layer is further interlocked with two adjacent layers to form a 2D + 2D → 3D parallel polycatenated structure. In MOF 2, when the Suc2− was placed by Aze2−, the Cd(II) centers are connected by Aze2− and 1,4-mbix into a 2D sql layer but without any water molecules. And two 2D sql layers interpenetrate with each other to generate a twofold 2D + 2D → 2D sheet. MOFs 1 and 2 display photoluminescence at 343 nm (λex = 288 nm) and 298 nm (λex = 271 nm), respectively. Luminescent quenching experiments show that 1 and 2 have good ability for detection of Fe3+ in deionized water with low detection limits as 0.58 μM for 1 and 0.54 μM for 2, respectively. Two MOFs also can serve as luminescent sensors for Fe3+ in real tap water and river water. The luminescent quenching of 1 and 2 toward Fe3+ can be attributed to the competition among the absorption of Fe3+ with the excitation and emission of two MOFs. [ABSTRACT FROM AUTHOR]

Two Cd(II) MOFs based on the 1,4-bis[(2-methyl-1H-imidazol-1-yl)-methyl]benzene (1,4-mbix) and succinate (Suc2−) or azelate (Aze2−) ligands have been hydrothermally synthesized, namely, {[Cd2(Suc)2(1,4-mbix)2]·5H2O}n (1) and [Cd(Aze)(1,4-mbix)]n (2). Both MOFs were structurally characterized by single-crystal X-ray diffraction. In MOF 1, the Cd(II) centers are connected by Suc2− and 1,4-mbix to generate a two-dimensional (2D) sql layer with (H2O)5 water cluster. Each 2D layer is further interlocked with two adjacent layers to form a 2D + 2D → 3D parallel polycatenated structure. In MOF 2, when the Suc2− was placed by Aze2−, the Cd(II) centers are connected by Aze2− and 1,4-mbix into a 2D sql layer but without any water molecules. And two 2D sql layers interpenetrate with each other to generate a twofold 2D + 2D → 2D sheet. MOFs 1 and 2 display photoluminescence at 343 nm (λex = 288 nm) and 298 nm (λex = 271 nm), respectively. Luminescent quenching experiments show that 1 and 2 have good ability for detection of Fe3+ in deionized water with low detection limits as 0.58 μM for 1 and 0.54 μM for 2, respectively. Two MOFs also can serve as luminescent sensors for Fe3+ in real tap water and river water. The luminescent quenching of 1 and 2 toward Fe3+ can be attributed to the competition among the absorption of Fe3+ with the excitation and emission of two MOFs. [ABSTRACT FROM AUTHOR]