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Both an excess and shortage of iron(III), away from normal permissible limits, can induce serious disorders, therefore its detection is significant, but still remains a challenge. Luminescent metal–organic frameworks (LMOFs) are a class of attractive materials for the detection of Fe3+ ions. However, improvement in their hydrolytic stability, speed, sensitivity, and selectivity of function is the key to the advanced application of LMOFs in an aqueous environment. Herein, two hydrostable LMOFs, Zn-DTA and Cd-DTA, based on the π-conjugated aromatic ligand 2,5-di(1H-imidazol-1-yl)terephthalic acid (H2DTA), were selected as highly efficient sensors for the rapid, sensitive and selective detection of Fe3+ in aqueous solutions. On the basis of the rigid structure and multiple coordination sites of the H2DTA ligand, Zn-DTA and Cd-DTA possess brilliant stability and excellent fluorescence emission. Both of them exhibit high selectivity (Ksv = 8400 and 6420 M−1) and high sensitivity (0.82 and 1.07 μM) for the rapid detection (less than 30 s) of small quantities of Fe3+ (0.2 mg mL−1) in water. It is worth noting that the compounds not only remain stable in the water for a long time but also maintain structural integrity at high temperatures. To the best of our knowledge, Zn-DTA and Cd-DTA, as two exceptionally stable MOF chemosensors used for the selective detection of Fe3+, show very rare behavior compared to the reported Zn/Cd-MOFs. The quenching mechanism for such a high selectivity can be mainly explained by the competition between the absorption of Fe3+ and the excitation of the compounds. Moreover, the introduced carboxyl O atoms of Zn-DTA additionally donate their lone-pair electrons to the Fe3+ ions, leading to enhanced detection ability. Our work reveals the enormous potential of LMOFs as an appealing platform upon which to construct sensing materials. [ABSTRACT FROM AUTHOR]

Four coordination polymers (CPs) based on H 2 tbta ligand, namely, [Zn(tbta) (bmbp)] n (1), {[Cd 0.5 (tbta) (H 2 O)] n ·(Hbia) (H 2 O)} (2), [Cu 1.5 (tbta) (OH) (bi) (H 2 O)] n (3) and [Cd(tbta) (ei) 2 ] n (4) have been synthesized and characterized (H 2 tbta = 2,3,5,6-tetrabromoterephthalic acid, bmbp = 4,4'-dimethyl-2,2'-bipyridine, bia = 1H-benzo[d]imidazol-2-amine, bi = 1H-benzo[d]imidazole, ei = 2-ethyl-1H-imidazole). Single-crystal X-ray diffraction analyses illustrate 1 and 4 exhibit 1D chains, and compound 1 and 4 are hydrogen-bonded into a 2D layer to form a 3D supramolecular structure. Compounds 2 and 3 show 2D layered structures and further expand to 3D supramolecular structures through hydrogen bonds. Structural comparisons indicate that the position of coordination sites and substituent groups plays a crucial role in the control of the final structures. Besides, the photoluminescence properties of compounds 1 , 2 , 4 and UV–vis spectra of 3 have been investigated in the solid state at room temperature. Image 1 • Four CPs based on H 2 tbta ligand were synthesized and structurally characterized. • The auxiliary ligands drastically affect the formation of low-dimensional structures. • The UV–vis spectrum and luminescence properties were studied. [ABSTRACT FROM AUTHOR]

Semi-rigid 6-(carboxymethoxy)-2-naphthoic acid (H 2 CNA) was successfully synthesized as a ligand containing O-bridging atom. Six coordination polymers based on H 2 CNA ligand and transition metal ions were successfully synthesized under the hydrothermal or solvothermal conditions, which named [Zn(CNA)] n (1), [Cd(CNA) (H 2 O)] n (2), [Co(HCNA) 2 (H 2 O) 4 ] (3), [Ni(HCNA) 2 (H 2 O) 4 ] (4), [Cu(CNA) (H 2 O)] n (5), [Ni(CNA) (H 2 O)] n (6). Single crystal structural analysis revealed that 1 , 2 , 5 and 6 are shown as 2D structures, and 3 – 4 displays 0D structures. All the structures assembled into 3D supramolecular networks by hydrogen bonding interaction. The thermal stability, luminescent properties and UV–vis spectra of these coordination polymers were discussed in detail. In addition, 5 has good adsorption ability for Congo Red with good selectivity. We synthesized and characterized six CPs based on semi-rigid 6-(carboxymethoxy)-2-naphthoic acid. Image 1 • Semi-rigid 6-(carboxymethoxy)-2-naphthoic acid (H 2 CNA) ligand was synthesized. • Six coordination polymers based on H 2 CNA ligand were synthesized. • Compound 5 has good adsorption ability for Congo Red with good selectivity. [ABSTRACT FROM AUTHOR]

Four coordination polymers, namely, [Zn (DBT) (4,4′-dmbpy) (H 2 O)] n (1), [Co(DBT) (2,2′-bpy) (H 2 O)] n (2), [Zn (DBT) (2,2′-bpy)] n (3), [Zn (DBT) 0.5 (2,2′-bpy) 2 ·(HDBT−)] n (4) (H 2 DBT ​= ​2,5-dibromoterephthalic acid, 4,4′-dmbpy ​= ​4,4′-dimethyl-2,2′-bipyridyl and 2,2′-bpy ​= ​2,2′-bipyridyl) have been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, IR and thermogravimetric (TG) analysis. These four compounds remained stable until 150 ​°C, and the major quality loss (83–90%) occurred between 150 and 700 ​°C. In mixed ligands system, the main ligand H 2 DBT exhibits monodentate or bidentate bridging coordination modes and the auxiliary ligands 4,4′-dmbpy and 2,2′-bpy both possess bidentate chelate coordination modes. An objective of this study was to investigate the pivotal role of chelating ligands in the formation of low dimensional structures. As the bipyridyl ligands occupy the coordination site, compounds 1 – 3 all display two dimensional structures and 4 shows 1D chains, of which compounds 1 and 2 are isomorphic. The hydrogen bonds and π-π stacking work together in the formation of 3D supramolecular structure of these four compounds. Besides, we investigated their photoluminescence properties in the solid state at room temperature. The compounds 1 , 3 and 4 exhibited good fluorescence performance, and their strong emission peaks were located at 447 ​nm (λex ​= ​285 ​nm) for 1 , 427 ​nm (λex ​= ​330 ​nm) for 3 , and 412 ​nm (λex ​= ​310 ​nm) for 4. Image 1 • Four CPs based on H 2 DBT ligand were synthesized and structurally characterized. • Low-dimensional crystals were obtained by changing experimental conditions. • The luminescence properties were studied. [ABSTRACT FROM AUTHOR]

Three novel coordination polymers, formulated as {[Zn(1,4-bmimb)(PhAA)2]·H2O}n (1), [Cu(1,4-bmimb)0.5(2,6-PyDC)]n (2), and {[Cu(1,4-bmimb)0.5(2-PAC)(HCOO)]·2H2O}n (3) (1,4-bmimb = 1,4-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene; PhAA = phenylacetic acid; 2,6-PyDC = pyridine-2,6-dicarboxylic acid; 2-PAC = 2-pyrazinecarboxylic acid), were synthesized by the self-assembly of mixed ligands with Zn(II) and Cu(II) under solvothermal conditions and characterized by means of single-crystal X-ray diffraction, X-ray powder diffraction, infrared spectra, thermogravimetric analysis, fluorescence spectra and UV-vis absorption spectra. 1 is shown as a Z-shaped chain, which is formed by Zn2+, PhAA ligands, and 1,4-bmimb ligands, and is assembled into a 3D structure by hydrogen bonding and π···π interaction. Similarly, 2 displays a single chain, which is built by Cu2+, 2,6-PyDC ligands, and 1,4-bmimb ligands, and is assembled into a 3D structure by hydrogen bonding and π···π interaction. 3 possesses a 1D ladder structure, which is formed by Cu2+, 2,6-PyDC ligands, and 1,4-bmimb ligands, and is assembled into a 3D structure by hydrogen bonding. The luminescence properties (for 1) and UV-vis spectrum (for 2 and 3) were also studied and discussed. [ABSTRACT FROM AUTHOR]

Four coordination polymers (CPs) based on bis-imidazole ligands (1,2-bimb and 1,2-bmimb), namely, {[Zn(1,2-bimb)(2,5-dtpa)] H2O}n (1), {[Cd2(1,2-bimb)2(5-hipa)2] 2H2O} (2), {Zn2(1,2-bimb)(L)(CH3COO) DMF·2H2O}n (3) and {Cd(1,2-bmimb)(3-npa)}n (4), have been synthesized by solvothermal reactions (1,2-bimb = 1,2-bis((1H-imidazol-1-yl)methyl)benzene, 1,2-bmimb = 1,2-bis((2-methyl-1H-imidazol-1-yl)methyl)benzene, 2,5-H2dtpa = 2,5-diaminoterephthalic acid, 5-H2hipa = 5-hydroxyisophthalic acid, H3L= 3,3′,3′′-(2,4,6-trioxo-1,3,5-triazinane-1,3,5-triyl)tripropanoic acid, 3-H2npa = 3-nitrophthalic acid) and structurally verified by single-crystal X-ray diffraction analyses and further characterized by powder X-ray diffraction (PXRD), elemental analyses and infrared spectroscopy (IR). Complex 1 and 2 show a dinuclear 2D layered structure. Complex 4 exhibits a two-dimensional network consisting of [Cd(3-npa)]n and [Cd(1,2-bmimb)]n chains. Both 1,2 and 4 display a 4-connected sql topology sheet, which can be further expanded into a 3D supramolecular network through π···π interaction between layers. Complex 3 features a 3D (3,6)-connected {42·6}·{44·610·8}-3,6T24 topology structure consisting of 2D bilayers. Structural comparison reveals that it is not only the substituents at different positions of ancillary ligands and the primary bis(imidazole) linkers that play crucial roles in the control of the final structures. Besides, the photoluminescence properties of 1–4 have been investigated in the solid state at room temperature. [ABSTRACT FROM AUTHOR]