This work presents for the first time the synthesis of a novel nanoscale Fe-MOFs/Eu-MOFs heterostructure, in which spherical Fe-MOFs with a large surface area were introduced as a matrix for the well-dispersed growth of rodlike Eu-MOFs. The obtained Fe-MOFs/Eu-MOFs materials exhibit excellent magnetic resonance/optical imaging capacity and satisfactory drug delivery behavior.

A pair of novel enantiomerically chiral clusters, R/S-[Zn4(HL)2(L)2·(CH3OH)2]·(NO3)2, have been obtained via the self-assembly of R/S-H2L Schiff base ligands with divalent zinc nitrate (H2L = 2-[(1-benzyl-2-hydroxy-ethylimino)-methyl]-6-methoxy-phenol). The compounds were characterized by single-crystal X-ray diffraction, elemental analysis and infrared spectroscopy. Their structures reveal that the enantiomers are not only in a chiral space group but also have a non-centrosymmetric polar packing arrangement. Both clusters display ferroelectric behavior at room temperature. Impressively, the clusters show well-defined ferroelectric hysteresis loops with high Ps values at a relatively high frequency of 100 Hz, which is very rarely in the field of molecule-based ferroelectrics.In this work, a pair of novel enantiomerically chiral Zn clusters have been successfully obtained by the self-assembly of R/S-H2L Schiff base ligands with divalent zinc nitrate. The luminescence emission spectra and ferroelectric hysteresis loops of these two zinc clusters have also been investigated at room temperature.Download high-res image (166KB)Download full-size image

•A ratiometric luminescence sensing method is developed.•This is the first chemical sensor for Cd2+ and F− via Ln-MOF.•A recyclable vaporluminescent sensor has been realized.A ratiometric luminescence sensing method is developed and makes the chemically stable Eu metal–organic framework to be the first bifunctional chemical sensor for Cd2+ and F− ions with naked-eye observation in the field of sensing applications utilizing luminescent Ln-MOFs. This is the first example of luminescent colorimetric sensor caused by the direct dual emissions of a single Ln-MOF. A recyclable vapoluminescent sensor for HCl and NH3 by the naked eye has also been realized.A luminescent Eu-MOF is successfully designed to be a novel bifunctional chemical sensor and a vapoluminescent sensor.Download high-res image (191KB)Download full-size image

•A flower-like structure of ZIF-67 was synthesized.•It presents high photocatalytic activity to CR.•The product could be collected conveniently by magnets.As organic dyes are a major group of water pollutants, the development of materials for the removal of dyes is of great significance for the environment. Here, a novel flower-like Fe3O4@ZIF-67 photocatalyst was synthesized using a simple method at room temperature. It was found that the Fe3O4@ZIF-67 exhibited the ability of degrading Congo red (CR) quickly under visible light irradiation in a short time after adsorption equilibrium. Free radical trapping experiments revealed that the photo-induced active species superoxide radical (•O2−) and holes (h+) were the predominant active species in the photocatalytic system. In addition, results demonstrated that the Fe3O4@ZIF-67 can be magnetically recycled, and maintain high photocatalytic activity after reuse over five cycles with no obvious decrease in the removal efficiency. It suggested that the synthesized material had a potentially promising application for CR removal from waste water.A flower-like structure of ZIF-67 loaded with Fe3O4 was synthesized by a facile method. It showed high photocatalysis activity that can degradate congo red (CR) completely in a short time.Download high-res image (196KB)Download full-size image

•A 3D porous metal-organic framework [Tb(H4btca)∙ 3H2O]n has been synthesized.•Tb-MOF displays excellent thermo-stability and chemical stability.•Tb-MOF can be used as a luminescence prober for selectively and rapidly quantitative sensing F− in aqueous solution.An extremely stable Tb metal-organic framework (Tb-MOF), namely [Tb(H4btca)∙ 3H2O]n (H4btca = [1,1′-biphenyl]-2,3,3′,5′-tetracarboxylic acid), was synthesized under hydrothermal condition. The single-crystal X-ray diffraction indicated Tb-MOF exhibits a 3D structure with 1D channel, which crystallizes as an orthorhombic system with a Pccn space group. In addition, Tb-MOF displays bright green luminescence under the irradiation of UV light at 254 nm. Meanwhile, the investigations showed that Tb-MOF possessed excellent thermal and pH stability. More importantly, it can selectively and rapidly sense F− among proprietary halide and pseudohalide ions, and can be used for quantitative detecting F−.An extremely stable terbium metal − organic framework (Tb-MOF) was synthesized under hydrothermal condition. It can selectively and rapidly sense F− among proprietary halide or pseudohalide anions as a luminescence prober, and can be used for quantitative detection of F− in aqueous solution.Download high-res image (145KB)Download full-size image

Five coordination polymers based on pyridine–tricarboxylate ligands formulated as [Zn(HL1)] (1), [Cd2(L1)(phen)2(OH)]·2H2O (2), [Co(HL1)(H2O)2] (3), [Co3(L1)2(H2O)8]·4(H2O) (4) and [Mn3(L2)2(4,4′-bpy)2(H2O)2] (5) (H3L1 = 4-(2,4-dicarboxylphenyl) picolinic acid, H3L2 = 5-(3′,5′-dicarboxylphenyl) nicotinic acid, phen = 1,10-phenanthroline, 4,4′-bpy = 4,4′-bipyridine) were synthesized under hydrothermal conditions. Compound 1 exhibits a 2D distorted square-grid network based on [Zn(μ-Ocarboxylate)(COO)]n chains. Compound 2 displays a 2D square-grid network based on tetranuclear [Cd4(μ3-OH)2(Ocarboxylate)2(COO)2] units in which Cd(II) ions are bridged by the mixed bridges of (μ3-OH)2(μ-Ocarboxylate)2. Compound 3 exhibits a 2D network based on [Co(COO)]n chains in which Co(II) ions are bridged by a single syn–anti carboxylate bridge (μ-COO). Compound 4 features a 3D framework based on 2D layers which are further interlinked by Co(II) ions, containing [Co(COO)]n chains which Co(II) ions are also bridged by a single syn–anti carboxylate bridge similar with that in 3. Compound 5 shows a 2D network based on trinuclear [Mn3(COO)6(H2O)2] units in which Mn(II) ions are bridged by the mixed bridges of (μ-Ocarboxylate)(COO)2. These compounds have been characterized by IR spectra, TGA and powder XRD pattern. Compounds 1 and 2 exhibit intense luminescence properties in the solid state at room temperature. Magnetic studies for compounds 3–5 demonstrated that the single carboxylate bridge in 3 and 4 transmits weak antiferromagnetic interactions between Co(II) ions while the mixed bridges of (μ-Ocarboxylate)(COO)2 transmit moderate antiferromagnetic interactions between Mn(II) ions in 5.

A luminescent lanthanide metal–organic framework [Tb(L)(H2O)5]n solvents (Tb-MOF, H2L− = 3,5-dicarboxyphenol anion ligand) with a 2D network structure was synthesized. The size of the Tb-MOF single crystal can reach up to 6 mm; such large-scale single crystals of MOFs are rarely reported in the literature. Tb-MOF exhibits a strong green luminescence induced by the efficient antenna effect of the ligands. Importantly, it shows an excellent recognition ability on detecting the Pb2+ ion, which is a noxious inorganic pollutant and causes permanent damage to human health and living environments. The perfect linear correlation between the luminescence intensity of Tb-MOF and the concentration of the Pb2+ ions provides this crystal as a reliable and easy-to-use luminescent sensor, which can be applied in pollutant monitoring. As far as we know, it is the first example of a high-efficiency luminescent MOF sensor with millimeter level for detecting Pb2+ ions at a very low concentration with a detection limit down to 10−7 M.

As a result of their extraordinarily large surfaces and well-defined pores, the design of a multifunctional metal–organic framework (MOF) is crucial for drug delivery but has rarely been reported. In this paper, a novel drug delivery system (DDS) based on nanoscale MOF was developed for use in cancer diagnosis and therapy. This MOF-based tumor targeting DDS was fabricated by a simple postsynthetic surface modification process. First, magnetic mesoporous nanomaterial Fe-MIL-53-NH2 was used for encapsulating the drug and served as a magnetic resonance contrast agent. Moreover, the Fe-MIL-53-NH2 nanomaterial exhibited a high loading capacity for the model anticancer drug 5-fluorouracil (5-FU). Subsequently, the fluorescence imaging agent 5-carboxyfluorescein (5-FAM) and the targeting reagent folic acid (FA) were conjugated to the 5-FU-loaded Fe-MIL-53-NH2, resulting in the advanced DDS Fe-MIL-53-NH2-FA-5-FAM/5-FU. Owing to the multifunctional surface modification, the obtained DDS Fe-MIL-53-NH2-FA-5-FAM/5-FU shows good biocompatibility, tumor enhanced cellular uptake, strong cancer cell growth inhibitory effect, excellent fluorescence imaging, and outstanding magnetic resonance imaging capability. Taken together, this study integrates diagnostic and treatment aspects into a single platform by a simple and efficient strategy, aiming for facilitating new possibilities for MOF use for multifunctional drug delivery.Keywords: fluorescence imaging; magnetic resonance imaging; multifunctional MOFs; nanoscale MOFs; targeted drug delivery;

Photocatalytic behaviors of isostructural metal-doped metal–organic frameworks were rarely discussed in the field of metal–organic frameworks. Herein, a series of 2D isomorphous Co2+/Zn2+ metal-doped metal–organic frameworks, namely, [M(tpbpc)(bdc)0.5·H2O]·solvent (M = Co (1), Co0.545Zn0.455 (2), Co0.2165Zn0.7835 (3), Co0.0258Zn0.9742 (4), Zn (5), Htpbpc = 4′-[4,2′;6′,4″] terpyridin-4′-yl-biphenyl-4-carboxylic acid, H2bdc = 1,4-benzenedicarboxylic acid), have been successfully synthesized under solvothermal conditions, and the crystal structures were testified by the single-crystal X-ray diffraction analysis and PXRD analysis. The photocatalysis activities of 1–5 were investigated by photodegradation of methyl orange (MO) experiments under visible light irradiation. Results indicated that 1 is nearly an inactive photocatalyst for degradation of MO, whereas 5 exhibits excellent photocatalytic activity under visible light irradiation. Interestingly, when Co2+ ions are gradually replaced by Zn2+ ions in the metal–organic frameworks, photocatalytic activities of which have improved gradually from 1 to 5; this offers a controllable regulation of photocatalytic properties by changing metal ions in isostructural metal-doped MOFs.

•A pair of enantiomeric trinuclear nickel (II) clusters based on chiral threonine Schiff-base ligands has been synthesized.•Circular dichroism (CD) spectra indicate the enantiomeric nature of the pair of clusters.•Magnetic susceptibility studies show ferromagnetic interactions between the Ni (II) centers within the trinuclear units.A pair of enantiomeric trinuclear Ni (II) clusters formulated as Ni3[(HLL-Thr)2(H2O)4(benzoate)2]·2EtOH (1) and Ni3[(HLD-Thr)2(H2O)4(benzoate)2]·2EtOH (2) (H3L = 3-hydroxy-2-[(2-hydroxy-3-methoxy-benzylidene)-amino]-butyric acid), have been successfully synthesized via the assembly of a pair of enantiomerically chiral amino acid Schiff-base ligands, benzoate anion with divalent nickel salt in an air-exposed water-ethanol solutions. The structures are characterized through single-crystal-X-ray diffraction analysis. The structures of complex 1 and 2 both contain enantiomeric linear trinuclear Ni3[(HL)2(H2O)4(benzoate)2]·2EtOH units in which Ni (II) ions are bridged by the mixed bridges of (μ-Ophenol)2(μ-COO)2. Circular dichroism (CD) spectra indicated the enantiomeric nature of the pair of clusters. Magnetic susceptibility studies in the temperature range of 2–300 K illustrated that complex 1 and 2 show ferromagnetic interactions between the Ni (II) centers within the trinuclear units while antiferromagnetic interactions among inter-trinuclear units.A pair of enantiomeric trinuclear nickel (II) clusters exhibit complete opposite Cotton effects and ferromagnetic interactions between the Ni (II) centers within the trinuclear units while antiferromagnetic interactions among inter-trinuclear units.Download high-res image (76KB)Download full-size image

•A novel Zn-MOF has been prepared easily under mild synthetic conditions with the drug ibuprofen incorporated as a ligand.•The Zn-MOF can be delaminated to obtain MOF nanosheets via the surfactant-assisted synthetic method.•Compared to bulk Zn-MOF, the obtained nanosheets show remarkable pH-controlled ibuprofen release.Crystalline metal–organic framework (MOF) nanosheets have been fabricated from a new bulk MOF (1) which is assembled by ZnII metal ions as nodes and the drug ibuprofen as ligand. Surfactant-assisted synthetic method was used to control the growth of bulk MOF to obtain MOF nanosheets and the obtained MOF nanosheets exhibit good biodegradability and pH-controlled ibuprofen release.Download high-res image (240KB)Download full-size image

A microporous Gd-MOF, [Gd6(L)3(HL)2(H2O)10]·18H2O·x(solvent) (1), has been successfully synthesized by a solvothermal reaction between Gd(NO3)3·6H2O and the multidentate π-conjugated ligand, H4L, which has a Lewis basic pyridyl site (H4L = 5,5′-(pyridine-2,5-diyl)-isophthalic acid). The crystal structure shows that compound 1 consists of Gd3 units, which are further interlinked by multicarboxylate ligands to form a 2D network. A solid sample of 1 emits bright blue light, which can be assigned to H4L ligand-centered emission. Interestingly, the luminescence of finely ground particles of 1 dispersed in water shows high sensitivity and selectivity towards trace amounts of o-, m-, and p-nitrophenol (NP) and Fe3+ ions with good linearity, which indicates that 1 can be used as a multi-responsive luminescence sensor for the detection of o-, m-, and p-NP and Fe3+ ions in an aqueous system.

A sequence of isostructural lanthanide metal–organic frameworks, namely [Ln(Hbtca)(phen)] (Ln = Tb (1) and Eu (2), H4btca = biphenyl-2,3,3′,5′-tetracarboxylic acid and phen = 1,10-phenanthroline), has been successfully synthesized under a hydrothermal reaction. The single X-ray diffraction studies reveal that the structure of the Ln-MOFs is a double-paned 2D network. Thermogravimetric analysis has been used to characterise the Ln-MOFs, which display good thermal stability. By adjusting the ratio of Eu3+ to Tb3+, a series of co-doped lanthanide coordination polymers [EuxTb1−x(Hbtca) (phen)] (0 ≤ x ≤ 1) has been successfully acquired, with emission colors changes from an initial red, to yellow and lastly green. Excitingly, a white emission material has been successfully obtained with the ratio Eu0.0167Tb0.9833-MOF and the CIE coordinates (0.3199, 0.3381), these values are very close to the standardized values (0.3333, 0.3333).

A novel series of zinc coordination polymers, namely, {[Zn(H2btca)2(bpt)]·H2O}n (1), {Zn2(btca)(PyBIm)(H2O)}n (2) and {[Zn1.5(Hbtca)(pytpy)]·H2O}n (3), have been assembled using zinc nitrates, an conjugated carboxylate ligand H4btca and different N-donor ligands under hydrothermal conditions (H4btca = 1,1′-biphenyl-2,3,3′,5′-tetracarboxylic acid, bpt = 1H-3,5-bis(4-pyridyl)-1,2,4-triazole, PyBIm = 2-(4-pyridyl)benzimidazole, pytpy = 2,4,6-tris(4-pyridyl)pyridine). Single crystal X-ray diffractions conformed that the three compounds are 1-D beaded chain-like structure, 2-D layered network and 3-D porous structures, respectively. The diverse architectures are derived from the different N-donor ligands used during the self-assembling process. Elemental analysis, infrared spectra and luminescence of all the coordination polymers have also been investigated. The diverse structures display different luminescence properties. This result extends the relationship between the structures and luminescence properties.In this work, three zinc coordination polymers from 1D to 3D have been successfully obtained by centering on metal–carboxylate systems with structural modulation directed by N-donor derivatives of various geometries as auxiliary ligands. The luminescence emission spectra of these three zinc coordination polymers have also been investigated at room temperature.

The synthesis, structural characterization, and magnetic properties of four related heterometallic complexes with formulas [DyIII2CoII(C7H5O2)8]·6H2O (1), [DyIII2NiII(C7H5O2)8]·(C7H6O2)2 (2), TbIII2CoII(C7H5O2)8 (3), and DyIII2CdII(C7H5O2)8 (4) were reported. Each of complexes has a perfectly linear arrangement of the metal ions with two terminal LnIII (LnIII = DyIII, TbIII) ions and one central MII (MII = CoII, NiII, CdII) ion. It was found that 1–3 displayed obvious magnetic interactions between the spin carriers according to the direct current (dc) susceptibility measurements. Alternating current (ac) magnetic susceptibility measurements indicate that complexes 1–4 all exhibit single-molecule magnet (SMM) behavior, while the replacement of the diamagnetic CdII by paramagnetic ions leads to a significant slowing of the relaxation thanks to the magnetic interactions between 3d and 4f ions, resulting in higher relaxation barrier for complexes 1 and 2. Moreover, both Dy2Co and Dy2Ni compounds exhibit dual relaxation pathways that may originate from the single ion behavior of individual DyIII ions and the coupling between DyIII and CoII/NiII ions, respectively, which can be taken as the feature of 3d–4f SMMs. The Ueff for 1 of 127 K is a relatively high value among the reported 3d–4f SMMs. The results demonstrate that the magnetic coupling between 3d and 4f ions is crucial to optimize SMM parameters. The synthetic approach illustrated in this work represents an efficient route to design nd–4f based SMMs via incorporating suitable paramagnetic 3d and even 4d and 5d ions into the d–f system.

An extremely thermostable magnesium metal–organic framework (Mg-MOF) is reported for use as a highly selective and sensitive, instantaneous and colorimetric sensor for Eu3+ ions. There has been extensive interest in the recognition and sensing of ions because of their important roles in biological and environmental systems. However, only a few of these systems have been explored for specific rare earth ion detection. A robust microporous Mg-MOF for the recognition and sensing of Eu3+ ions with high selectivity at low concentrations in aqueous solutions has been synthesized. This stable metal–organic framework (MOF) contains nanoscale holes and non-coordinating nitrogen atoms inside the walls of the holes, which makes it a potential host for foreign metal ions. Based on the energy level matching and efficient energy transfer between the host and the guest, the Mg-MOF sensor is both highly selective and sensitive as well as instantaneous; thus, it is a promising approach for the development of luminescent probing materials with unprecedented applications and its use as an Eu3+ ion sensor.

In our efforts toward the rational design and systematic synthesis of porous 3D MOFs, three 3D frameworks of Zn-MOFs ([Zn(BDC)(TIB)]·3H2O (Zn-MOF-1) (TIB = 1,3,5-tri(1H-imidazol-1-ly) benzene and H2BDC = 1,4-dicarboxybenzene), [Zn(BDA)(TIB)2/3]n (Zn-MOF-2) (H2BDA = 4,4′-biphenyl-dicarboxylic acid) and [Zn3(BDC)2(BDA)(TIB)2]n (Zn-MOF-3)) were successfully synthesized, based on different multicarboxylate ligands through solvothermal reactions. The resulting MOFs show similar 3D structures with different pore sizes which lead to distinct selective adsorption for organic dyes. Remarkably, Zn-MOF-1 exhibits an excellent capacity to adsorb CR (congo red) with high selectivity, and it maintains an almost identical adsorption performance after being recycled several times.

A series of BiOCl/SnO2 heterojunctions exhibiting exceptional visible light photocatalytic performance have been successfully prepared using a two-step solution route. The physical and chemical properties of the as-prepared samples were characterized by a range of techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET), photoluminescence spectroscopy (PL), Mott–Schottcky measurement and surface photovoltage spectroscopy (SPS). It's found that SnO2 nanoparticles with average particle size of ∼4 nm were uniformly dispersed on the {110} facets of BiOCl nanosheets and a heterojunction was formed at the interface between SnO2 and BiOCl. A defect state referenced to oxygen vacancies and vacancy associates play a vital role in reducing the band gap energy of SnO2 and BiOCl, respectively. With well-defined defect chemistry and heterostructure, the conjunction of two wide band-gap semiconductors (SnO2 and BiOCl) may lead to visible light harvesting and enhanced photocatalytic performance. The photocatalytic activities of the BiOCl/SnO2 heterojunction photocatalysts were evaluated by measuring the degradation of rhodamine B (RhB) under visible light irradiation. As was expected, the BiOCl/SnO2 composites displayed highly enhanced photocatalytic activity in comparison to the individual counterpart. The PL and SPS spectra confirmed that the formation of a p–n heterojunction between BiOCl and SnO2 can markedly accelerate the separation rate and inhibit the recombination of photo-induced electro–hole pairs, thus promoting the photocatalytic activity. As a consequence of well-modulated electronic structures, defect centers and heterostructure, the photocatalytic performance of BiOCl/SnO2 heterojunctions was well regulated and optimized.

Sandwich-structured SiO2@Ag@SnO2 and inverse SiO2@SnO2@Ag using SiO2 spheres as cores have been systematically synthesized through hydrothermal treatment. The crystal structure, morphology, size, composition and specific surface area of products were investigated by XRD, SEM, TEM (HRTEM), XPS, UV-vis and N2 adsorption–desorption instruments. It was found that both Ag nanoparticles and SnO2 layers were successfully decorated or coated on the surface of the matrix. The investigation of photocatalytic properties indicated that the SiO2@Ag@SnO2 heterostructure possessed an excellent photocatalytic ability superior to the SiO2@Ag, SiO2@SnO2 and even the inverse sample SiO2@SnO2@Ag, for the degradation of Rhodamine B (RhB) driven by UV light. The results indicated that Ag nanoparticles acted as the trapping centers for photo-induced electrons, and thus promoted the separation of photo-induced electron–hole pairs and charge migration. The enhanced photocatalytic ability of the heterostructure SiO2@Ag@SnO2 compared to the inverse sample SiO2@SnO2@Ag was possibly due to the larger exposed surface area under UV light irradiation, larger contact interfacial area and larger specific surface area of SiO2@Ag@SnO2 than SiO2@SnO2@Ag. Furthermore, the photocatalyst SiO2@Ag@SnO2 displayed benign recyclability in that its photocatalytic activity was still preserved after 5 cycles.

The ordered mesoporous material SBA-15 (FCSBA-15) with an enhanced hydrothermal stability was successfully synthesized from natural kaolin in the presence of a fluorocarbon surfactant. FCSBA-15 was further used as the support for Fe/BiOCl with the aim of exploring its Fenton-like catalytic performance toward the degradation of 2-nitrophenol. Based on characterization techniques including X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), no phases referring to the Fe species were observed, suggesting that the Fe3+ ions may be present on the surface of flower-like BiOCl. It is noted that the Fe3+ ions could lead to a morphological reconstruction from BiOCl nanosheets to BiOCl flowers. The obtained Fe/BiOCl–FCSBA-15 exhibited an excellent degradation efficiency for 2-nitrophenol, which reached nearly 100% within 40 min by optimizing parameters such as the H2O2 dosage, pH value, temperature, Fe/Bi molar ratio and Bi/Si molar ratio. The finding reported here is important and may help to develop novel mesoporous matrix based systems for advanced catalysts.

There has been extensive interest in the construction of grid-type supramolecular complexes because of their important roles in material science. However, only few of these compounds have been explored for selective adsorption of dyes. Two novel grid-type architectures composed of mixed valence copper ions and polynitrogen heterocyclic ligands have been successfully synthesized. Interestingly, one of the grid-type architectures with modest grid size could efficiently and selectively adsorb dye molecules.

A new luminescent two-dimensional europium metal–organic framework [Eu6(L)3(HL)2(H2O)10]·10H2O·x(solvent) (1) has been successfully prepared by the solvothermal reaction of Eu(NO3)3·6H2O and the multidentate π-conjugated ligand H4L (H4L = (5,5′-(pyridine-2,5-diyl)-isophthalic acid)) which has a Lewis basic pyridyl site. The solid sample of 1 emits high bright red light which can be readily observed by the naked eyes when excited at 358 nm at ambient temperature. Interestingly, the luminescence of fine grinding 1 particles dispersed in ethanol can be sensitively and selectively quenched by adding trace amounts of o-, m- and p-nitrophenol (NP), which reveals that 1 can be used as a luminescence sensor for the detection of o-, m- and p-NP.

•First trinuclear Mn(II) magnetic system with mixed (μ-COO)2(μ2-Ocarboxylate) bridges from a new zwitterionic ligand L1.•First trinuclear Co(II) magnetic system with mixed (μ-COO)2 (μ-H2O) bridges from a new zwitterionic ligand L2.•The (μ-COO)2(μ2-Ocarboxylate) and (μ-COO)2(μ-H2O) bridges transmit AF exchange within the Mn3 and Co3 units respectively.Two new Mn(II) and Co(II) coordination polymers with azide and zwitterionic dicarboxylate ligands L1 and L2 (L1 = [4-((1-carboxylatobenzyl)pyridimium-3-yl) benzoic acid] chloride, L2 = [1,1′-bis(4-carboxylatobenzyl)-4,4′-bipyridinium] dichloride) were synthesized and structurally and magnetically characterized. They are formulated as [Mn3(L1)4(N3)(CH3CH2OH)(H2O)]ClO4·4H2O (1) and [Co3(L2)4(N3)2(H2O)2]·4NO3 (2). Compound 1 contains two different linear trinuclear [Mn3(COO)8(CH3CH2OH)2]2 − and [Mn3(COO)6(H2O)2(N3)2]2 − units built from the mixed bridges of (μ-COO)2(μ2-Ocarboxylate). The trinuclear units are alternately linked into 1D chains by L1. Compound 2 contains linear trinuclear [Co3(N3)2(COO)4(H2O)2] units built from the mixed bridges (μ-COO)2(μ-H2O). Magnetic studies demonstrated that the mixed triple bridges are antiferromagnetic in compounds 1 and 2.Two new linear Mn(II)3 and Co(II)3 magnetic systems with mixed carboxylate–oxygen bridges derived from two zwitterionic ligands were obtained. The mixed carboxylate–oxygen bridges transmit antiferromagnetic interactions between M(II) ions.

Two pairs of novel enantiomerically chiral clusters R/S-[NaMnIIMnIII3L3(μ3-O)] (R/S-1) and R/S-[Na2MnII2MnIII6L6(μ3-O)2] (R/S-2) have been obtained via the self-assembly of R/S-H2L Schiff base ligands and different auxiliary ligands (N3−, dca−) with divalent manganese salt in an air-exposed methanol–ethanol solution. The structures of R/S-1 and R/S-2 were characterized by single-crystal X-ray diffraction analysis and powder X-ray diffraction. When the dicyanamide anion serves as an auxiliary ligand in the assembling reaction system, a pair of enantiomeric clusters R/S-[NaMnIIMnIII3L3(μ3-O)] (R-1 and S-1) with a trigonal bipyramid configuration were obtained, while another pair of enantiomeric clusters R/S-[Na2MnII2MnIII6L6(μ3-O)2] (R-2 and S-2) were formed in the case of the azide. Interestingly, the skeleton configuration of R/S-2 can be described as a 3-fold EO-azide bridging double trigonal bipyramid of [NaMnIIMnIII3L3(μ3-O)]2via MnII vertices. Circular dichroism (CD) spectra demonstrated the enantiomeric nature of the two pairs of clusters. Detailed direct current (DC) magnetic susceptibility studies in the temperature range 2–300 K suggested that R-1 and R-2 showed predominantly antiferromagnetic interactions between the manganese centers.

Four new polynuclear clusters [NaMnIII3MnII(HL)3(μ4-O)(μ1,1-N3)3]ClO4·CH3CH2OH·(H2O)3 (1), [NaMnIII3MnII(HL)3(μ4-O)(μ1,1-N3)2(μ1,3-N3)]ClO4·CH3CH2OH·H2O (2), [NaMnIII3MnII(HL)3(μ4-O)(HCOO)3]ClO4·(H2O)4 (3) and [NaMnIII3MnII(HL)3(μ4-O)(PhCOO)(H2O)2](ClO4)2·H2O·PhCOO·PhCOOH·CH3OH (4) have been obtained via self-assembly between 3-((2-hydroxy-3-methoxybenzylidene)amino)propane-1,2-diol (H3L: condensed from o-vanillin and 3-amino-1,2-propanediol) and the auxiliary bridges (N3−, HCOO−, PhCOO−, H2O) with Mn(ClO4)2·6H2O in the air-exposed methanol solution. The structures of 1–4 all contain [NaMnIII3MnII] units and show a very similar trigonal propeller-like shape. The valences of the metal ions were determined by detection of the Jahn–Teller distortion visible for MnII,III, and confirmed by bond-valence sum (BVS) calculations. Three MnIII ions and one MnII ion take the shape of a super-tetrahedron with the MnII ion lying above the triangular [Mn3O] plane constructed from three MnIII ions linked by a central μ4-O atom. The NaI ion which lies below the [Mn3O] plane is linked with MnIII ions through the oxygen atoms from Schiff base ligands. The main structural difference in the four clusters is caused by the different bridging modes among MnIII ions. A structural comparison of 1–4 demonstrates that the auxiliary ligands play a key role in governing the coordination motifs. Moreover, the magnetic properties of these clusters exhibit dominating antiferromagnetic exchange interaction between spin carriers of MnII,III.

A novel double-paned extended 2D network (TbMOF–COOH) containing large volume lantern-like open pores was prepared. With active uncoordinated carboxyl groups pointing to the interior of the pores, TbMOF–COOH has a high selectivity and sensitivity for Fe3+ ions via a luminescence quenching mechanism.

This work explores a hydrothermal route to synthesis of self-doped SiO2/SnO2/SnO2:Sn2+ nanostructures with controlled hierarchical structures and lattice parameters for tunable optical and photocatalytic properties. The effects of Sn2+ self-doping in the SnO2 lattice on the local structure, electronic structure, and photodegradation of methyl orange were systematically investigated. It is found that two layers of SnO2 and SnO2:Sn2+ nanocrystals with thicknesses of 13 and 8 nm were coated on SiO2 spheres showing monodispersed features. By Sn2+ doping, a blue shift of the Sn 3d XPS binding energy was observed, which is thought to be mainly related to the difference in electronegativity of Sn4+, Sn2+ and variation of lattice parameters. In contradiction to the quantum size effect, the self-doped SiO2/SnO2/SnO2:Sn2+ nanostructures showed an abnormal red shift of band gap energy, which is related to doping effects and variations of lattice parameters. With well-defined lattice structure and electronic structure, the photocatalytic performance of SiO2/SnO2/SnO2:Sn2+ nanostructures can be well regulated and optimized.

•First azide-bridged magnetic system derived from L was reported.•A new example of the Co(II) systems with double μ-1,3 N3 bridges was demonstrated.•First real complex showing the point symbol (62·74)(64·7·9)2 topology was shown.•The double μ-1,3 N3 bridges transmit antiferromagnetic interactions in compound 1.A new cobalt(II) coordination polymer formulated as [Co2(N3)4(L)]n·4n H2O (1) (L = tetrakis(3-pyridyloxymethylene) methane) was synthesized by a diffusion method, and structurally and magnetically characterized. In compound 1, the Co(II) chains with double end-to-end (EE) azide bridges are interlinked by the tetrapyridyl ligands into a three-dimensional framework. With both Co(II) and L as 4-connecting nodes, the structure represents the first real example of the 4-connected net topology with point symbol (62·74)(64·7·9)2. Magnetic studies demonstrated that the double EE azide bridges transmit antiferromagnetic interactions along the chain.The first azide-bridged magnetic system derived from a quadritopic organic bridging ligand (L) was obtained. And the double μ-1,3-N3 bridges transmit antiferromagnetic interactions between Co(II) ions along the chain.

•A new luminescent 2D MOF was designed and synthesized.•The MOF can recognize nitrobenzene with high selectivity and sensitivity.•The MOF is a potential sensor for nitro explosives.A novel luminescent terbium metal-organic framework [Tb(HL)(H2O)4]·H2O (1) has been successfully prepared by the facile hydrothermal reaction of Tb(NO3)3·6 H2O and the π-conjugated ligand H4L (H4L=1,1′-biphenyl-2,3,3′,5′-tetracarboxylic acid). Single crystal structure analysis reveals that 1 exhibits a 2D layered structure. The solid sample of 1 emits high bright green light which can be readily observed by the naked eye when excited at 288 nm at ambient temperature. Interestingly, the luminescence of fine grinding 1 particles dispersed in ethanol can be selectively and sensitively quenched by nitroaromatic compounds, which indicates that 1 is a potential luminescent sensory material for nitro explosives.

A novel 3D microporous compound [Zn3(Httca)2(4,4′-bpy)(H2O)2]n (MOF–COOH) containing uncoordinated carbonyl groups pointing to the pores was prepared. The uncoordinated carbonyl groups in the channels can act as postsynthetic modification sites for cation exchange. The MOF–COOH compound can effectively and selectively serve as an antenna for sensitizing the visible-emitting Tb3+ cation.

Two series of lanthanide-based coordination polymers, [Ln(HCPOB)(CPOB)(H2O)2]n [Ln = Eu(a1), Gd(a2), Tb(a3), Dy(a4), Ho(a5), Er(a6)] and [Ln(HCPOB)(CPOB)]n [Ln = Eu(b1), Gd(b2), Tb(b3), Dy(b4), Ho(b5), Er(b6)], have been synthesized using an asymmetric semi-rigid V-shape multicarboxylate ligand [H4CPOB = 2-(4-carboxyphenoxy)benzoic acid] by a hydrothermal method at different temperatures. Series a were obtained at 130 °C and have one-dimensional (1D) chain architectures, while series b were synthesized at 180 °C and exhibit three-dimensional (3D) structures. Interestingly, temperature-dependent XRD patterns for 1D compounds indicate that the 1D structure changes to form the 3D coordination polymers on heating the crystals. Single crystals of series a can transform into crystals of series b without any significant change in crystal quality. The variations from 1D to 3D coordination structures are attributed to variable coordination modes of multicarboxylate ligand H2CPOB. In addition, we have studied the luminescent properties of Eu3+, Tb3+, and Dy3+ compounds of series a and series b, and found that series a give very weak luminescence because of coordinated water molecules existing in the complexes. Due to the “antenna effect” or “luminescence sensitization”, series b exhibit much stronger fluorescent intensity than that of series a.

Homochiral crystallizations of single-stranded helical coordination polymers were constructed using the V-shaped bridging ligand dicyanamide (μ1,5-dca−) and chelate auxiliary ligands. The enantiomeric nature of 1 and 2 is directly induced by the chirality of the auxiliary ligands. Whereas, the homochirality feature for 3 stems from the spontaneous symmetry breaking in crystallization.

The reactions of lanthanide nitrates with a Schiff-base ligand HL (2-[(2-hydroxypropylimino)methyl] phenol) have produced five new complexes with formula as [Ln2(L)3(NO3)3]CH3OH(Ln=Gd 1, Tb 2, Dy 3, Ho 4, Er 5). These new complexes are characterized by elemental analysis, IR and X-ray diffraction, as well as fluorescence spectra. Single-crystal X-ray diffraction analysis reveals that all the complexes crystallize in the trigonal system, space group R-3. Fluorescence spectroscopy of Tb(III) and Dy(III) complexes display strong characteristic metal-centered fluorescence in solid state, which demonstrates that luminescence is sensitized by the effective energy-transfer from ligand to the metals. The fluorescence lifetimes of complex 2 and 3 are also determined.Highlights► The crystal structures of these complexes are determined by using single-crystal X-ray diffraction. ► Tb(III) and Dy(III) complexes display strong characteristic metal-centered fluorescence in solid state. ► The effective energy-transfer from ligand to the metals controls the overall efficiency of emission of Tb(III) or Dy(III).

Three new zinc(II) complexes Zn(L1)2 (1), Zn2L2(OAc)3 (2) and Zn2L3(OAc)3 (3) have been synthesized by using Zn(OAc)2·2H2O and potentially multidentate Schiff base ligands HL1 (2-((1-hydroxybutan-2-ylimino)methyl)-6-methoxyphenol), HL2 (2-((1-hydroxy-2-methyl-propan-2-ylimino)methyl)-6-methoxyphenol) and HL3 (2-((2-hydroxypropylimino)-methyl)-6-methoxyphenol), respectively. These Schiff base ligands are the condensation product of o-vanillin and corresponding amino alcohols. All the three complexes 1, 2 and 3 have been characterized by elemental analysis, IR, single crystal X-ray diffraction and fluorescence studies. Structural studies reveal that 1 is a mononuclear complex whereas in dinuclear complexes 2 and 3 the two Zn(II) centers are held together by deprotonated Schiff base ligands and acetates. All the synthesized complexes display intraligand (π → π*) fluorescence and can potentially serve as photoactive materials.Three blue luminescent zinc(II) complexes have been synthesized by using Zn(OAc)2·2H2O and potentially multidentate Schiff base ligands. The structures of all the three complexes 1, 2 and 3 have been determined by single crystal X-ray diffraction.Highlights► Three zinc(II) complexes with blue luminescent which display intraligand (π → π*) fluorescence has been synthesized. ► The fluorescence intensity is greatly enhanced by the coordination of (ZnII) with Schiff base ligands. ► The supramolecular interactions increase the conformational rigidity of chromophore groups and thus the emission intensity is much stonger.

Three new manganese(III) compounds have been synthesized via in situ ligand transformation and oxidation of Mn(II) ions. In the presence/absence of N3− anion in the reaction solutions, the dinuclear/mononuclear Mn(III) coordination compounds were formed, respectively. A structural analysis of the dinuclear compounds (1, 2) shows that the six coordination Mn(III) atoms are linked by two methanolato oxygen atoms from two ligands to form a rectangular arrangement of the metal ions and oxygen atoms. In complex 3, two facially coordinating tridentate ligands are bound to the Mn(III) ion, resulting in a MnN4O2 chromophore with an axially-compressed octahedral geometry. In addition, variable-temperature magnetic analysis of 1 shows that a weak antiferromagnetic coupling interaction was mediated through the methanolato oxygen bridge between two Mn(III) ions and the exchange parameter is given as J = − 3.6 cm− 1.Graphical abstractThree new manganese(III) compounds have been synthesized via in situ ligand transformation and oxidation of Mn(II) ions. The crystal structure and magnetic properties of these complexes have been studied.Highlights► Three Mn(III) compounds have been synthesized via in situ ligands transformation. ► In the presence/absence of N3–, the di-/mononuclear Mn(III) compounds were formed. ► The crystal structure and magnetic properties of these complexes have been studied.

Considering the combination of lanthanide-doped CaWO4 nanophosphor and mesoporous matrix may contribute to superior luminescent properties, CaWO4:Eu3+/SBA-15 composites were successfully synthesized in a mild condition. The physicochemical properties of the resultant composites were carefully characterized by X-ray diffraction, high-resolution transmission electron microscopy, inductive coupled plasma optical emission spectroscopy (ICP), N2 adsorption–desorption, Fourier transform infrared spectroscopy, and luminescence spectra. It’s found that the incorporation of CaWO4:Eu3+ showed no obvious impact on the ordered mesostructure of the host matrix SBA-15, which, however, led to a decrease of BET surface area from 836 to 187 m2 g−1 for pure SBA-15 and CES (0.5), respectively. ICP results indicated that the real loaded amount of CaWO4:Eu3+ in SBA-15 host was lower than the initial molar ratios (x) of CaWO4:Eu3+ to SBA-15 for all samples. The maximum loaded level of CaWO4:Eu3+ in SBA-15 is about 27.3 %. Moreover, the real Eu3+ dopant concentration increased with the initial molar ratios (x), which showed a maximum of about 6.51 % at x = 0.25. The resultant CaWO4:Eu3+/SBA-15 composites exhibited enhanced-luminescent properties than that of pure CaWO4:Eu3+ nanoparticles, which can be mainly attributed to the variation of Eu3+ dopant concentration and the host-protect effect through interaction between guest molecules and host matrix. The available large surface area, pore volume, and superior luminescent properties would facilitate future applications for the composites.

A discrete dysprosium cubane has been prepared and structurally characterized. Slow relaxation of magnetization in this complex is observed, which may stimulate further investigations into the dynamics of magnetization in lanthanide clusters with different topologies.

A novel 3D microporous compound [Zn3(Httca)2(4,4′-bpy)(H2O)2]n (MOF–COOH) containing uncoordinated carbonyl groups pointing to the pores was prepared. The uncoordinated carbonyl groups in the channels can act as postsynthetic modification sites for cation exchange. The MOF–COOH compound can effectively and selectively serve as an antenna for sensitizing the visible-emitting Tb3+ cation.

Two pairs of novel enantiomerically chiral clusters R/S-[NaMnIIMnIII3L3(μ3-O)] (R/S-1) and R/S-[Na2MnII2MnIII6L6(μ3-O)2] (R/S-2) have been obtained via the self-assembly of R/S-H2L Schiff base ligands and different auxiliary ligands (N3−, dca−) with divalent manganese salt in an air-exposed methanol–ethanol solution. The structures of R/S-1 and R/S-2 were characterized by single-crystal X-ray diffraction analysis and powder X-ray diffraction. When the dicyanamide anion serves as an auxiliary ligand in the assembling reaction system, a pair of enantiomeric clusters R/S-[NaMnIIMnIII3L3(μ3-O)] (R-1 and S-1) with a trigonal bipyramid configuration were obtained, while another pair of enantiomeric clusters R/S-[Na2MnII2MnIII6L6(μ3-O)2] (R-2 and S-2) were formed in the case of the azide. Interestingly, the skeleton configuration of R/S-2 can be described as a 3-fold EO-azide bridging double trigonal bipyramid of [NaMnIIMnIII3L3(μ3-O)]2via MnII vertices. Circular dichroism (CD) spectra demonstrated the enantiomeric nature of the two pairs of clusters. Detailed direct current (DC) magnetic susceptibility studies in the temperature range 2–300 K suggested that R-1 and R-2 showed predominantly antiferromagnetic interactions between the manganese centers.

An extremely thermostable magnesium metal–organic framework (Mg-MOF) is reported for use as a highly selective and sensitive, instantaneous and colorimetric sensor for Eu3+ ions. There has been extensive interest in the recognition and sensing of ions because of their important roles in biological and environmental systems. However, only a few of these systems have been explored for specific rare earth ion detection. A robust microporous Mg-MOF for the recognition and sensing of Eu3+ ions with high selectivity at low concentrations in aqueous solutions has been synthesized. This stable metal–organic framework (MOF) contains nanoscale holes and non-coordinating nitrogen atoms inside the walls of the holes, which makes it a potential host for foreign metal ions. Based on the energy level matching and efficient energy transfer between the host and the guest, the Mg-MOF sensor is both highly selective and sensitive as well as instantaneous; thus, it is a promising approach for the development of luminescent probing materials with unprecedented applications and its use as an Eu3+ ion sensor.

A luminescent lanthanide metal–organic framework [Tb(L)(H2O)5]n solvents (Tb-MOF, H2L− = 3,5-dicarboxyphenol anion ligand) with a 2D network structure was synthesized. The size of the Tb-MOF single crystal can reach up to 6 mm; such large-scale single crystals of MOFs are rarely reported in the literature. Tb-MOF exhibits a strong green luminescence induced by the efficient antenna effect of the ligands. Importantly, it shows an excellent recognition ability on detecting the Pb2+ ion, which is a noxious inorganic pollutant and causes permanent damage to human health and living environments. The perfect linear correlation between the luminescence intensity of Tb-MOF and the concentration of the Pb2+ ions provides this crystal as a reliable and easy-to-use luminescent sensor, which can be applied in pollutant monitoring. As far as we know, it is the first example of a high-efficiency luminescent MOF sensor with millimeter level for detecting Pb2+ ions at a very low concentration with a detection limit down to 10−7 M.

We report a luminescent Eu metal–organic framework (MOF) with a one-dimensional, open channel filled with water molecule assemblies; this MOF can serve as a dual-functional luminescent sensor for detecting temperature and humidity. Using this MOF, we have developed a self-calibrating ratiometric thermometer that operates within the cryogenic temperature range and simultaneously functions as a luminescent humidity sensor within the relative humidity (RH) range from 33.0% to 85.1%.