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Under the solvothermal condition, the reaction of 4,4′′-(1,3-phenylene)-bis[2,3′-bipyridine]-6-carboxylic acid (H2L1) with Mn(NO3)2·4H2O in dimethylacetamide (DMA) afforded a novel zero-dimensional (0D) metallomacrocycle, [Mn4(L1)4(H2O)8]·20H2O (1). However, in a similar solvothermal condition to 1, the reaction of H2L1 with Mn(OAc)2·4H2O in dimethylsulfoxide (DMSO) yielded one new three-dimensional (3D) metal–organic framework, [Mn(L1)]·4H2O·DMSO (2). Furthermore, other three 3D metal–organic frameworks, [M(L1)]·4H2O·DMSO (M = Cd (3), Cu (4) and Zn (5)), were obtained under the same solvothermal condition as 2, which are isostructural with 2. Interestingly, a novel two-dimensional (2D) metallomacrocycle network, [Zn2(L2)(H2O)3]·3H2O·DMA (6), was solvothermally synthesized through the reaction between 4,4′-(6,6′-([1,1′-biphenyl]-4,4′-diyl)bis(2-(4-carboxyphenyl)pyridine-6,4-diyl))dibenzoic acid (H4L2) and Zn(NO3)2·6H2O in DMA. 1–6 were fully characterized by infrared spectra, elemental analyses, thermogravimetric analyses, powder X-ray diffraction patterns, or single-crystal X-ray diffractions. The changes from 0D metallomacrocycle (1) to 3D isostructural metal–organic frameworks (2–5) are mediated by increasing solvent polarity (from DMA to relatively high polar DMSO) because the more polar DMSO solvent helps the coordination sites of L12− ligand to take part in coordination. More interestingly, 3, 5, and 6 achieve close to white-light emission upon excitation at 365 nm. The gas adsorption properties of 2–5 have also been investigated, and the results indicate that the CO2 adsorption capacities are relative to the framework stability of MOFs 2–5. The present work provides a promising approach to constructing novel metal–organic frameworks or metallomacrocycles and may open new perspectives for developing single-component white-light-emitting materials. [ABSTRACT FROM AUTHOR]

Four novel isostructural lanthanide metal–organic frameworks (Ln-MOFs), [Ln2(L)3(DMF)2(H2O)4]·2DMF (Ln = Eu(1), Tb(2), Gd(3) and Y(4); H2L = 4,4′-([2,4′-bipyridine]-4,6-diyl)dibenzoic acid; DMF = N,N-dimethylformamide), were solvothermally synthesized. These Ln-MOFs were characterized by IR spectroscopy, thermogravimetry, and powder X-ray diffraction methods. The single-crystal analysis reveals that in 1, three Eu3+ centres are linked together by two bidentate bridging carboxylate groups from two L2− ligands to form trinuclear secondary building units, which further construct a three-dimensional framework. These Ln-MOFs exhibit selective sensing of Fe3+ ions and Cr2O72− anions with better quenching constant values and lower detection limits. According to the tests, 3 and 4 show higher sensitivity and selectivity towards Fe3+ ions, but 2 reveals lower sensitivity and selectivity towards Fe3+ ions. Moreover, 1–4 display higher sensitivity and selectivity towards Cr2O72− anions. Notably, 3 is a rare Gd-MOF sensor for Fe3+ ions, and 4 is a rare Y-MOF sensor for Cr2O72− anions. Besides, the four Ln-MOFs can remain stable during the tests. The fluorescence quenching can be attributed to the competitive light absorption and the energy transformation between Ln-MOFs and Fe3+/Cr2O72− ions. Furthermore, the luminescence properties of Ln-MOFs have also been investigated. [ABSTRACT FROM AUTHOR]

A new three-connecting T-shaped ligand, (4-3′-pyridyl-,6-4′-carboxylphenyl)picolinic acid (H2L), was used to construct four coordination polymers: {[Mn(L)(H2O)2]·2H2O}n (1), {[Cd(HL)(Cl)]·0.5H2O}n (2), [Co(L)(H2O)]n (3) and {[Ni(L)(H2O)2]·1.5H2O}n (4). Based on this T-shaped ligand, one 1D ladder chain (1) and two unique 2D bilayers (2 and 3) were constructed. Regardless of the three-connecting L2− ligand, 4 only consists of an infinite 2D network, in which two L2− ligands bridge two NiII centres, leading to a rhombic grid motif that is further connected to four adjacent rhombic grids, resulting in a 2D polymeric network. Interestingly, both 2 and 3 possess rhombic voids and exhibit CO2 gas adsorption features. Because coordination polymer 2 possesses a larger pore size (11.60 × 7.86 Å)/volume (16.7%) than that of 3 (11.53 × 7.65 Å/10.2%), 2 exhibits higher CO2 adsorption capacities at 273 K. Furthermore, the magnetic properties and photoluminescence have also been investigated. The present work provides a promising approach to design a new T-shaped ligand and construct various coordination polymers or metal–organic frameworks, and then to tune CO2 adsorption properties. [ABSTRACT FROM AUTHOR]

A novel one-dimensional spiro-like chain coordination polymer with a blue-emission signal was solvothermally synthesized via the reaction of Zn2+ ions with organic ligand HL (4-(4-(2-chloroimidazo[1,2-a]pyridin-3-yl)-[2,3′-bipyridin]-6-yl)benzoic acid), which is further extended to a porous three-dimensional supramolecular framework, namely, the porous coordination polymer (PCP), [Zn(L)2]·2DMF (USTC-5). This PCP was characterized by IR spectroscopy, thermogravimetry, and single-crystal, and powder X-ray diffraction methods. USTC-5 possesses larger quasi-hexagonal channels with Lewis-base sites, and is a better CO2 adsorption or promising CO2/N2 selective material, suggesting potential application in gas separation. USTC-5 also can serve as a multi-responsive sensing material for detecting Fe3+, Cr2O72−, CrO42−, MnO4− and nitrobenzene (NB). Moreover, the mechanism of the selective luminescence quenching response for Cr2O72−, CrO42−, MnO4− and NB can be mainly ascribed to the competitive adsorption of excitation wavelength energy between USTC-5 and Cr2O72−, CrO42−, MnO4− or NB; meanwhile, Fe3+ ions diffused into the channels of USTC-5 and formed contacts with Lewis-base sites in USTC-5, leading to luminescence quenching. Significantly, USTC-5 displays reversible luminescence color switching in response to acid–base vapor stimuli, which originates from the conversion between the amorphous form and the crystal mediated by protonation–deprotonation processes. Such a stimuli-responsive conversion provides a promising approach to design and construct smart PCP materials. [ABSTRACT FROM AUTHOR]