Bimetal loaded graphitic carbon nitride with synergistic enhanced peroxidase-like activity for colorimetric detection of p-phenylenediamine.

In recent years, great progress has been made on the study of nanozymes with enzyme-like properties. Here, bimetallic Fe and Ni nanoclusters were anchored on the nanosheets of nitrogen-rich layered graphitic carbon nitride by one-step pyrolysis at high temperature (Fe/Ni-CN). The loading content of Fe and Ni on Fe/Ni-CN is as high as 8.0%, and Fe/Ni-CN has a high specific surface area of 121.86 m2 g-1. The Fe/Ni-CN can effectively oxidize 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, and exhibits efficient peroxidase-like activity, leading to a 17.2-fold increase compared to pure graphitic carbon nitride (CN). Similar to the natural horseradish peroxidase (HRP), the Fe/Ni-CN nanozyme follows catalytic kinetics. The Michaelis-Menten constant (Km) value of the Fe/Ni-CN nanozyme for TMB is about 8.3-fold lower than that for HRP, which means that the Fe/Ni-CN nanozyme has better affinity for TMB. In addition, the catalytic mechanism was investigated by combination of free radical quenching experiments and density-functional theory (DFT) calculations. The results show that the high peroxidase-like activity is due to the easy adsorption of H2O2 after bimetal loading, which is conducive to the production of hydroxyl radicals. Based on the extraordinary peroxidase-like activity, the colorimetric detection of p-phenylenediamine (PPD) was constructed with a wide linear range of 0.2-30 µM and a low detection limit of 0.02 µM. The sensor system has been successfully applied to the detection of residual PPD in real dyed hair samples. The results show that the colorimetric method is sensitive, highly selective and accurate. This study provides a new idea for the efficient enhancement of nanozyme activity and effective detection of PPD by a bimetallic synergistic strategy.

Interlayer interaction-force-tuned magnetic responses in CoII-tetrazolate-carboxylate system from canted antiferromagnet to field-induced metamagnet.

Interlayer magnetic couplings of low-dimensional magnets have significantly dominated magnetic behavior through skillful regulation of interlayer interacting forces. To identify interaction-force-regulated interlayer magnetic communications, two air-stable Co(II)-based coordination polymers (CPs), a well-isolated layered structure with approximately 12.6 Å interlayer separation and a carboxylate-extended three-dimensional framework with an inter-ribbon distance of 5.8 Å, have been solvothermally fabricated by varying polycarboxylate mediators in a ternary CoII-tetrazolate-carboxylate system. The layered CP with antiparallel-arranged {Co2(COO)2}n chains interconnected only via cyclic tetrazolyl linkages behaves as a spin-canted antiferromagnet with a Néel temperature of 2.6 K, due to strong intralayer antiferromagnetic couplings and negligible interlayer magnetic interactions. In contrast, the compact three-dimensional framework with corner-sharing Δ-ribbons tightly aggregated through µ2-η1:η1-COO- is a field-induced metamagnet from a canted antiferromagnet to a weak ferromagnet with a small critical field of Hc = 90 Oe. Apparently, these interesting magnetic responses reveal the importance of an interacting force from the magnetic subunits for the magnetic behavior of the molecular magnet, greatly enriching the magnetostructural correlations of transition-metal-based molecular magnets.

Bimetallic FeMn@C derived from Prussian blue analogue as efficient nanozyme for glucose detection.

In recent decades, nanomaterial-based artificial enzymes called nanozymes have received more and more attention and have been applied in biological, chemical, medical, and other fields. In this work, bimetallic FeMn@C was synthesized by calcination from the Prussian blue analogue. The synthesized bimetallic FeMn@C exhibits efficient peroxidase-like activity. The effect of Mn doping amount, catalytic kinetics, and mechanism of FeMn@C nanozyme was further studied in detail. The results show that the peroxidase-like activity of bimetallic FeMn@C is nearly 16 times higher than that of single-metal Fe@C. The peroxidase-like activity of FeMn@C originates from its production of radicals. Compared with natural enzymes, FeMn@C nanozyme has a better affinity for the substrates. Besides, FeMn@C nanozyme has better stability than natural enzymes. Because of its strong magnetism, FeMn@C nanozyme can be recycled easily and exhibits excellent recycling performance. Based on the good affinity of FeMn@C for H2O2, a rapid and selective colorimetric assay for glucose detection is constructed, with a wide linear range of 0.01-0.75 mM and low detection limit of 4.28 µM. This sensor has been successfully applied to the determination of glucose in fruit juice, showing good selectivity and accuracy. The synthesis of bimetallic FeMn@C provides a feasible way to design nanozymes with excellent catalytic activity, high stability, and easy separation.

Side-Group Effect on the Slow Relaxations of {Dy2} Single-Molecule Magnets with Confined N2O6 Donors.

Deep insights into and substantial enhancement of the effective anisotropy energy barrier for magnetization reversal (Ueff) are vitally important for the technological applications of dysprosium(III)-based single-molecule magnets (Dy-SMMs). To fully refine the ligand-field effect on spin relaxation, four centrosymmetric {Dy2} entities with formula [Dy2(CH3OH)2L2(RCOO)2] (H2L = 2-hydroxy-N'-((pyridin-2-yl)methylene)benzohydrazide) have been solvothermally prepared by varying the side groups of carboxylate coligands (RCOO-, R = CF3 for 1, H for 2, CH3 for 3, and Cp2Fe for 4). Structural analyses reveal that all of the DyIII carriers in 1-4 have the same N2O6 donor environments, and the non-coordinative R groups attached to the equatorial carboxylate bridges have not substantially changed the binding ability of the shortest Dy-Ophenolate bonds located at the axial position of the ligand field. Interestingly, the side groups have monotonically decreased the zero-field Ueff barriers of these weak antiferromagnetically coupled {Dy2} analogues from 721 K down to 379 K. Further electronic structure calculations demonstrate that the main magnetic axes of 1-4 are highly dominated by these comparable Dy-Ophenolate short bonds, and the g tensors have produced gradually increased transverse components responsible significantly for the decreased Ueff barriers. Additionally, thermally assisted relaxations occur preferably through the second (for 1) and the first (for 2-4) Kramer doublets. These interesting findings afford a new side-group effect to comprehensively understand the magnetostructural relationships and advance the rational design of high-performance Dy-SMMs.

NiO nanobelts with exposed {110} crystal planes as an efficient electrocatalyst for the oxygen evolution reaction.

The electrocatalytic oxygen evolution reaction (OER) is necessary and challenging for converting renewable electricity into clean fuels, because of its complex proton coupled multielectron transfer process. Herein, we investigated the crystal plane effects of NiO on the electrocatalytic OER activity through combining experimental studies and theoretical calculations. The experimental results reveal that NiO nanobelts with exposed {110} crystal planes show much higher OER activity than NiO nanoplates with exposed {111} planes. The efficient OER activity of the {110} crystal planes comes from their intrinsically high catalytic ability and fast charge transfer kinetics. Density functional theory (DFT) shows that the {110} crystal planes possess a lower theoretical overpotential value for the OER, leading to a high electrocatalytic performance. This research broadens our vision to design efficient OER electrocatalysts by the selective exposure of specific crystal planes.

Slow relaxation of Dy(III) single-ion magnets dominated by the simultaneous binding of chelating ligands in low-symmetry ligand-fields.

Electronic effect and geometry distortion of low-symmetry ligand-field on the anisotropy barrier (Ueff) of spin reversal have been compared in three Dy(III) single-ion magnets through the simultaneous binding of chelating ligands. The substitution of N,O-salicylaldoxime by N,N'-1,10-phenanthroline in the distorted triangular-dodecahedronal field sharply decreases the Ueff by 286 K due to an increase in non-preferred transverse anisotropy, while the geometry distortion with CShM = 1.569 went down to 1.376 only lowering the Ueff by 12 K. The co-coordination strategy of heterodonor ligands highlights the importance of ligand-surroundings on the relaxation dynamics.

Enhancing the Magnetic Anisotropy in Low-Symmetry Dy-Based Complexes by Tuning the Bond Length.

One mononuclear complex [Dy(Htpy)(NO3)2(acac)] (1) and a tpy--extended 1D chain {[Dy(CH3OH)(NO3)2(tpy)]·CH3OH}n (2) (Htpy = 4'-(4-hydroxyphenyl)-2,2':6',2''-terpyridine, Hacac = acetylacetone) were successfully designed to investigate the effect of bond length tuning around the DyIII cation on the magnetic dynamics of single-molecule magnets (SMMs). Interestingly, two magnetic entities possess the same local coordination sphere (N3O6-donor) as well as the configuration (Muffin, Cs) of dysprosium centers. Only a slight difference in structure results from purposefully substituting the acetylacetone ligand in 1 with hydroxyl oxygen from tpy- linkage and one methanol molecule in 2. However, the remarkable differences in dynamics behavior were clearly found between them. Compound 1 possesses a thermal-activated effective energy barrier (Ueff/kB) of 22.7 K under a 0 kOe direct current (dc) field and negligible hysteresis loop at 2.0 K, while complex 2 shows high-performance SMM behavior with the largest energy barrier of 354.36 K among the reported nine-coordinated DyIII-based systems and the magnetic hysteresis up to 4.0 K at a sweep rate of 200 Oe s-1. These experimental results combined with the previous reported data reveal that the shortest bond and the bond length difference around the DyIII center synergistically determine the dynamics of SMMs. The uniaxial anisotropy increases with the decrease of the shortest bond and the increase of the bond length difference, which is confirmed by the theoretical calculations.

Photo-oligomerization by shifting the coordination site in a luminescent coordination polymer.

A layered coordination polymer (CP) with the fine-tuned alignment of four diolefinic ligands has been designed by shifting the coordination site of the ligand. The trimeric and tetrameric cyclobutane derivatives were reversely achieved by the photoinitiated [2+2] cycloaddition of the CP due to the favorable Schmidt's distance. More interestingly, a dynamic fluorescence shift was observed during the photo-oligomerization and heat-cycloreversion of the CP system.

Photocatalytic hydrogen evolution activity over Pt-assisted metal-organic frameworks dominated by transition metal ions and local coordination environments.

Three isostructural pillared-layer frameworks with M-BDC-X layers supported by ditopic HL connectors, [M(HL)(BDC)0.5X] n (HL = 4'-(4-hydroxyphenyl)-4,2':6',4″-terpyridine, BDC = terephthalate, M = Cd, X = Cl for (1), M = Cd, X = formate for (2), and M = Co, X = formate for (3)), were solvothermally synthesized, and used as photocatalysts for Pt-assisted visible-light-initiated hydrogen evolution from water splitting. These water-durable frameworks exhibit varied hydrogen production rates of 361.2, 271.3, and 327.5 µmol · g-1 · h-1 in 12 h due to their slightly different donor environments of the octahedral CdII and CoII ions. Further experimental and theoretical investigations reveal that the metal ions and the local coordination surroundings have essentially dominated the conduction band minimum and electric resistance of the charge transport, which play highly important roles for the improved catalytic hydrogen evolution ability. These findings demonstrate the electronic effect of the slightly ligand field modifications on the boosting hydrogen generation activity in the noble metal-assisted MOF photocatalytic systems.

Encapsulated anion-dominated photocatalytic and adsorption performances for organic dye degradation and oxoanion pollutant capture over cationic Cu(i)-organic framework semiconductors.

Decontamination of industrial wastewater containing toxic organic dye molecules and oxoanions is urgently desirable for environmental sustainability and human health. Water-stable porous metal-organic frameworks (MOFs) have emerged as highly efficient photocatalysts and/or adsorbents for water purification through controllable integration of the constitutive requirements. To reveal the inclusion anion effect of microporous MOFs on wastewater treatment, two isostructural MOFs incorporating positive charge and semiconductive characteristics, {[Cu(tpt)]·3H2O·0.5SO4}n (1) and {[Cu(tpt)]·2H2O·ClO4}n (2, tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine), have been synthesized and employed as dual-functional materials for both dye photodegradation and oxoanion removal. The two MOFs possess the same 3-fold interpenetrating cationic backbones but are encapsulated by highly disordered sulfate or perchlorate in the open channels. These included anions have significantly tuned the hydrophilicity of the channels, extended the visible-light absorption, optimized the bandgap and decreased the conduction band potential. Under the low-energy irradiation of a 30 W LED lamp, MOF 1 has selectively and efficiently degraded rhodamine B compared to 2 with accelerated kinetics, resulting from the stronger reduction ability and less migration resistance of the photogenerated electrons. Instead, MOF 2 can quickly capture harmful MnO4- and Cr2O72- by exchanging with the entrapped ClO4-, with maximum adsorption amounts of 557 and 168 mg g-1, respectively, under ambient conditions. The improved decolorization of the aqueous solution over 2 benefits essentially from the shape and charge memory effect and the smaller hydration energy of ClO4- than SO42-. These interesting observations highlight the importance of the included anions inside the porous MOF semiconductors on wastewater treatment.

Substituent group-tunable hydrogen evolution activity observed in isostructural Cu(ii)-based coordination polymer photocatalysts.

Elucidations on the structure-activity correlations of non-Pt coordination polymer (CP)-based photocatalysts are highly significant for both the enhancement in catalytic activity and large-scale industrial applications of sustainable hydrogen from water splitting. Herein, three isostructural [Cu(HL)2(R-BDC)]n (denoted as Cu-CP-R, HL = 4'-(4-hydroxyphenyl)-4,2':6',4''-terpyridine, R-BDC = 2-R-1,4-benzenedicarboxylate, R = NO2, OH and Br) CPs were solvothermally synthesized by varying the substituents attached to benzenedicarboxylate, which together with two previously reported analogues (R = NH2 and H) were used as photocatalysts to systematically explore the substitution effect on the hydrogen evolution activity. These five CPs feature isomorphic layered motifs with axially elongated CuII octahedra extended alternately by ditopic HL and R-BDC2- connectors, in which R behaves structurally as a non-coordinate group. The hydrogen production rate over the Cu-CP-R photocatalysts increased from 0.21 to 2.34 mmol g-1 h-1, which followed the order of -NH2 > -NO2 > -H > -OH > -Br. Furthermore, the combined experimental and theoretical investigations reveal that the free R moiety significantly dominates the photocatalytic activity by shifting the d states of the CuII ion towards the Fermi level, controlling the potential of the conduction band and quickening the charge transfer ability. These important findings can provide informative hints for the design of high-performance, earth-abundant non-noble metal CP-based semi-conductive photocatalysts.

Hollow Zn-Co Based Zeolitic Imidazole Framework as a Robust Heterogeneous Catalyst for Enhanced CO2 Chemical Fixation.

The efficient chemical conversion of carbon dioxide (CO2 ) into value-added fine chemicals is an intriguing but challenging route in sustainable chemistry. Herein, a hollow-structured bimetallic zeolitic imidazole framework composed of Zn and Co as metal centers (H-ZnCo-ZIF) has been successfully prepared via a post-synthetic strategy based on controllable chemical-etching of the preformed solid ZnCo-ZIF in tannic acid. The creation of hollow cavities inside each monocrystalline ZIFs could be achieved without destroying the intrinsic frameworks, as characterized by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffraction technologies. The as-synthesized H-ZnCo-ZIF exhibited remarkable catalytic activity in the cycloaddition of CO2 with epoxides to the corresponding cyclic carbonates, outperforming the solid ZnCo-ZIF analogue due to the improved mass transfer originating from the hollow structure. More importantly, due to stabilization of metal centers in the ZIF framework by the tannic acid shell, H-ZnCo-ZIF exhibited good recyclability, and no activity loss could be observed in six runs. The present study provides a simple and effective strategy to enhance the catalytic performance of ZIFs by creating a hollow structure via chemical etching.

Self-supported Co-doped FeNi carbonate hydroxide nanosheet array as a highly efficient electrocatalyst towards the oxygen evolution reaction in an alkaline solution.

The evolution of molecular hydrogen from electrochemical water splitting has currently emerged as one of the promising strategies to address the ever-increasing energy crisis and environmental pollution. The development of low-cost, highly efficient and long-term durable electrocatalysts is still challenging for practical large-scale water splitting applications. Herein, a highly crystallized Co-doped FeNi carbonate hydroxide nanosheet array was strongly grown on a conductive nickel foam (Co-FeNi CH/NF) and was used as an oxygen evolution reaction (OER) electrocatalyst. The ternary Co-FeNi CH/NF electrode exhibited an improved OER activity and good durability for at least 20 hours. The electrode delivered current densities of 10 and 500 mA cm-2 at extremely low overpotentials of 202 and 254 mV along with a small Tafel slope of 37.5 mV dec-1 in a 1.0 M KOH electrolyte solution. The incorporation of an equivalent amount of cobalt into the trigonal FeNi CH crystal lattice significantly increased the electrochemical active surface area and reduced the electron transport resistance by effectively regulating the electronic structure of the resultant electrocatalyst. These interesting observations highlight the importance of the subtle combinations of the active earth-abundant metals with electronic structure modulations.

A heterometallic sodium(i)-europium(iii)-organic layer exhibiting dual-responsive luminescent sensing for nitrofuran antibiotics, Cr2O72- and MnO4- anions.

The detection of nitrofuran antibiotics and toxic inorganic anions is currently necessary and challenging because their abuse and/or residuals have caused severe environmental pollution and illness. A heterometallic two-dimensional (2D) layered complex, {[Eu2Na(Hpddb)(pddb)2(CH3COO)2]·2.5(DMA)}n (1), was solvothermally synthesized and structurally and photophysically characterized. Pairs of acetate aggregated {Eu2Na(CH3COO)2} chains are periodically interconnected by V-shaped 4,4'-(pyridine-2,6-diyl)dibenzolate (pddb) linkers. More interestingly, the layered complex exhibits a bright red emission and can efficiently discriminate nitrofuran antibiotics by luminescent quenching with a strong quenching constant (Ksv) and low detection limit (LOD) of 4.93 × 104 M-1 and 0.64 µM for nitrofurazone, 4.42 × 104 M-1 and 0.68 µM for nitrofurantoin as well as 2.13 × 104 M-1 and 1.06 µM for furazolidone. Additionally, 1 can also probe trace amounts of toxic Cr2O72- and MnO4- anions with Ksv = 6.45 × 103 M-1 and LOD = 5.35 µM for Cr2O72- and Ksv = 2.84 × 103 M-1 and LOD = 5.99 µM for MnO4- anions. These interesting results indicate that heteromatallic coordination polymers can serve as favorable dual- or even multiple-responsive luminescence sensors to selectively recognize different kinds of contaminants.

Efficient detection of a biomarker for infant jaundice by a europium(iii)-organic framework luminescence sensor.

Efficient detection of excess bilirubin in human serum and urine is highly important for the early diagnosis of infant jaundice. A highly stable Eu(iii)-based microporous framework with bent {Eu(COO)} chains interconnected by pairs of T-shaped 4,4'-(4,4'-bipyridine-2,6-diyl)dibenzoate (bpydb2-) linkers, {[Eu(H2O)(HCOO)(bpydb)]·solvent} n (1), was solvothermally synthesized and used as a chemical sensor for bilirubin response under clinically-applicable visible-light excitation. Due to the significant synergetic effect of the inner filter effect and photoinduced electron transfer, 1 can effectively probe trace amounts of bilirubin in aqueous solution through fluorescence decay with a strong quenching constant of 6.40 × 104 M-1 and low detection limit of 1.75 µM. More importantly, a portable test paper made from 1 was further developed to achieve qualitative, naked-eye visualized differentiation for the biomarker in clinical applications. These interesting findings highlight the importance of the π-conjugated antenna ligand for clinically applicable Ln-MOF sensors.

Three microporous metal-organic frameworks assembled from dodecanuclear {NiLn} subunits: synthesis, structure, gas adsorption and magnetism.

Three isostructural heterometallic metal-organic frameworks (MOFs) {[Ln2Ni(OAc)5(HL)(L)]·solvent molecules}n (H2L = 2-hydroxyimino-N-[1-(2-pyrazinyl)ethylidene]-propanohydrazone, Ln = Dy for 1, Tb for 2 and Gd for 3) were solvothermally synthesized by varying rare-earth metal ions with different electron configurations. Their crystal structures, gas adsorption and magnetic behaviors were fully investigated. The three isomorphous MOFs exhibit three-dimensional microporous frameworks with two different orientated dodecane metallic {NiIILnIII(HL)}6 metallomacrocycles alternately connected by {LnIII(L)} connectors, in which an empty one-dimensional channel decorated by the basic hydrazone interior is generated. Due to their LnIII-independent microporous nature, the activated sample of 1 as a representative example has a significant CO2 uptake up to 42.2 cm3 g-1 and an unusually high CO2/N2 and CO2/CH4 adsorption selectivity of up to 98.8 and 16.8 at 298 K and 100 kPa. Magnetically, apparent antiferromagnetic interactions for both 1 and 2 as well as ferromagnetic coupling for 3 are respectively observed at low temperature resulting from the competition of magnetic anisotropy and intermetallic ferromagnetic superexchange. Additionally, 1 with highly anisotropic DyIII spin shows slow magnetization relaxation under zero dc field, whereas 3 possessing isotropic GdIII ions displays a significant cryogenic magnetocaloric effect with a maximum entropy change of 26.6 J kg-1 K-1 at 3.0 K and 70 kOe. These interesting results can provide valuable information on gas separation-based multifunctional 3d-4f MOF materials.

Amino group promoted photocatalytic hydrogen evolution activity observed in two copper(ii)-based layered complexes.

Two copper(ii)-based layered complexes with or without the amino group, [Cu(HL)2(NH2-BDC)]n (1) and [Cu(HL)2(BDC)]n (2) (HL = 4'-(4-hydroxyphenyl)-4,2':6',4''-terpyridine, NH2-H2BDC = 2-amino-1,4-benzenedicarboxylic acid and H2BDC = 1,4-benzenedicarboxylic acid), were solvothermally synthesized and used as photocatalysts to accelerate hydrogen production from water splitting. The amino group modified 1 has exhibited greatly enhanced photocatalytic activity with a hydrogen production rate of 2.34 mmol g-1 h-1 under visible light irradiation, which is almost double that of 2. Density functional theory calculations, electrochemical impedance spectroscopy and transient photocurrent tests demonstrate that the higher catalytic activity of 1 than 2 is a result of the enriched electron density around the CuII center by the amino group, which facilitates the charge transfer from the conduction band to the water molecule.

In situ synthesis of molybdenum carbide/N-doped carbon hybrids as an efficient hydrogen-evolution electrocatalyst.

The development of non-precious metal based electrocatalysts for the hydrogen evolution reaction (HER) has received more and more attention over recent years owing to energy and environmental issues, and Mo based materials have been explored as a promising candidate. In this work, molybdenum carbide/N-doped carbon hybrids (Mo2C@NC) were synthesized facilely via one-step high-temperature pyrolysis by adjusting the mass ratio of urea and ammonium molybdate. The Mo2C@NC consisted of ultrasmall nanoparticles encapsulated by N-doped carbon, which had high specific surface area. They all exhibited efficient HER activity, and the Mo2C@NC with a mass ratio of 160 (Mo2C@NC-160) showed the best HER activity, with a low overpotential of 90 mV to reach 10 mA cm-2 and a small Tafel slope of 50 mV dec-1, which was one of the most active reported Mo2C-based electrocatalysts. The excellent HER activity of Mo2C@NC-160 was attributed to the following features: (1) the highly dispersed ultrasmall Mo2C nanoparticles, which exhibited high electrochemically active surface areas; (2) the synergistic effect of the N-doped carbon shell/matrix, which facilitated the electron transport.

High-nuclear heterometallic oxime clusters assembled from triangular subunits: solvothermal syntheses, crystal structures and magnetic properties.

Three series of six pyrazine-2-amidoxime (H2pzaox)-based 3d-4f clusters, {Ln8Ni6}, {Ln5Ni10} and {Ln5Ni8} (Ln = Dy and Gd), were solvothermally synthesized in the absence or presence of different coligands, and were structurally and magnetically characterized. The unusual ring-shaped {Ln8(µ3-OH)4} core in the two {Ln8Ni6} complexes is generated by four corner-sharing triangle {Ln3(µ3-OH)} units, which are further connected to six outer NiII ions by twelve deprotonated H2pzaox ligands in three common binding modes. By contrast, the remaining four clusters contain only two corner-sharing {Ln3(µ3-OH)} triangles, which interact with peripheral NiII ions through fourteen H2pzaox ligands in five (for {Ln5Ni10}) and four (for {Ln5Ni8}) different bridging ways. Thus, the interesting core motifs observed in these clusters depend significantly on the number of the triangular {Ln3(µ3-OH)} subunits and their connectivity manner with the singly and doubly deprotonated pyrazine-2-amidoxime ligand. Additionally, weak ferromagnetic superexchange in the {Dy5Ni10} and {Ln5Ni8} clusters and antiferromagnetic coupling in {Ln8Ni6} and {Gd5Ni10} clusters was respectively mediated by versatile oximate bridges between the intramolecular LnIII and NiII ions. Furthermore, the three DyIII-derived aggregates exhibit slightly temperature-dependent magnetic relaxations under a zero dc field, and the three GdIII-based clusters display large magnetic entropy changes of 23.5 J kg-1 K-1 for {Gd8Ni6}, 19.4 J kg-1 K-1 for {Gd5Ni10}, and 22.4 J kg-1 K-1 for {Ln5Ni8} at 4.0 K and 70 kOe. These interesting results are helpful for the understanding of oximate-based 3d-4f coordination chemistry and their structure-function relationships.

A micrometer-sized europium(iii)-organic framework for selective sensing of the Cr2O72- anion and picric acid in water systems.

A micrometer-sized europium(iii)-organic framework with asymmetric binuclear metal subunits extended by 4,5-dichlorophthalaten (DCPA), [Eu2(H2O)(DCPA)3]n, was easily obtained using a reverse microemulsion method. The framework exhibits good dispersibility, excellent thermal and environmental stability and easy regeneration ability. More importantly, the complex displays strong red emission and can selectively and sensitively detect both inorganic Cr2O72- anions (Ksv = 8.7 × 103 M-1) and organic picric acid contaminants (Ksv = 1.07 × 104 M-1) in water systems through fluorescence quenching. A luminescent film of 1 was further prepared and successfully used to detect the Cr2O72- anion in an aqueous system. These interesting results indicate that the well-dispersed europium(iii)-organic framework can serve as a promising dual-responsive luminescent sensor for environmental pollutant monitoring.