Bimetallic MOFs-derived coral-like Ag-Mo2C/C interwoven nanorods for amperometric detection of hydrogen peroxide.

Coral-like Ag-Mo2C/C-I and blocky Ag-Mo2C/C-II composites were obtained from one-step in situ calcination of [Ag(HL)3(Mo8O26)]n·nH2O [L: N-(pyridin-3-ylmethyl) pyridine-2-amine] under N2/H2 and N2 atmospheres, respectively. The coral-like morphology of Ag-Mo2C/C-I is composed of interwoven nanorods embedded with small particles, and the nano-aggregate of Ag-Mo2C/C-II is formed by cross-linkage of irregular nanoparticles. The above composites are decorated on glassy carbon electrode (GCE) drop by drop to generate two enzyme-free electrochemical sensors (Ag-Mo2C/C/GCE) for amperometric detection of H2O2. In particular, the coral-like Ag-Mo2C/C-I/GCE sensor possesses rapid response (1.2 s), high sensitivity (466.2 µA·mM-1·cm-2), and low detection limit (25 nM) towards trace H2O2 and has wide linear range (0.08 µM~4.67 mM) and good stability. All these sensing performances are superior to Ag-Mo2C/C-II/GCE, indicating that the calcining atmosphere has an important influence on microstructure and electrochemical properties. The excellent electrochemical H2O2 sensing performance of Ag-Mo2C/C-I/GCE sensor is mainly attributed to the synergism of unique microstructure, platinum-like electron structure of Mo2C, strong interaction between Mo and Ag, as well as the increased active sites and conductivity caused by co-doped Ag and carbon. Furthermore, this sensor has been successfully applied to the detection of H2O2 in human serum sample, contact lens solution, and commercial disinfector, demonstrating the potential in related fields of environment and biology. Graphical abstract.

Ladder chain Cd-based polymer as a highly effective adsorbent for removal of Congo red.

Developing of high effective and fast-rate adsorbent materials has been recently attracted intensive attentions all over the world due to organic dye polluted water treatment. However, few studies have been reported on the ultrahigh-capacity and fast-rate removal of Congo red. In this work, a new stable Cd-based coordination polymer exhibits excellent adsorption performance towards Congo Red. This ladder chain [Cd4(H2L)4(H2O)8(NDS)]n·3n(NDS) (I) (H2L = N1,N2-bis(pyridin-3-ylmethyl) ethane-1,2-diamine, 1,5-H2NDS = 1,5-naphthalene disulfonic acid) has been successfully synthesized by the hydrothermal reaction. At room temperature, the experimental adsorption capacity of coordination polymer (I) towards Congo red can reach up to 16,880 mg g-1 in 20 min (pH = 2.0-3.2), and its higher capacity and faster rate are all better than those in reported inorganic and metal-organic frameworks absorbents. The adsorption process is spontaneous and endothermic reaction, and fits well with the second-order kinetics, Langmuir and Scatchard isotherm adsorption models. The excellent adsorption performance of (I) towards Congo red is related to the strong electrostatic, various hydrogen bonding and π-π stacking interactions under acidic conditions.

Well-designed strategy to construct helical silver(I) coordination polymers from flexible unsymmetrical bis(pyridyl) ligands: syntheses, structures, and properties.

In this Article, self-assembly of AgX (X = NO3(-) and ClO4(-)) salts and four flexible unsymmetrical bis(pyridyl) ligands, namely, N-(pyridin-2-ylmethyl)pyridin-3-amine (L1), N-(pyridin-3-ylmethyl)pyridin-2-amine (L2), N-(pyridin-4-ylmethyl)pyridin-2-amine (L3), and N-(pyridin-4-ylmethyl)pyridin-3-amine (L4), results in the formation of eight helical silver(I) coordination polymers, [Ag(L)(NO3)]n [L = L1 (1), L2 (2), L3 (3), L4 (4)] and [Ag(L)(ClO4)]n [L = L1 (5), L2 (6), L3 (7), L4 (8)], which have been characterized by elemental analysis, IR, TG, PL, and powder and single-crystal X-ray diffraction. The alternating one-dimensional (1-D) left- and right-handed helical chains are included in achiral complexes 1-3 and 5-8. By contrast, the ligand L4 only alternately bridges Ag(I) cation to form the 1-D right-handed helical chain in complex 4. The pitches of these helical chains locate in the range 5.694(5)-17.016(6) Å. Meanwhile, the present four unsymmetrical bis(pyridyl) ligands in the eight complexes present diverse cis-trans and trans-trans conformation and facilitate the construction of helical structures. Moreover, the solid-state luminescent emission intensities of the perchlorate-containing complexes are stronger than those of nitrate-containing complexes at room temperature.

Porous Cr2O3 Architecture Assembled by Nano-Sized Cylinders/Ellipsoids for Enhanced Sensing to Trace H2S Gas.

How to achieve high sensing of Cr2O3-based sensors for harmful inorganic gases is still a challenge. To this end, Cr2O3 nanomaterials assembled from different building blocks were simply prepared by chromium salt immersion and air calcination with waste scallion roots as the biomass template. The hierarchical architecture calcined at 600 °C is constructed from nanocylinders and nanoellipsoids (named as Cr2O3-600), and also possesses multistage pore distribution for target gas accessibility. Interestingly, the synergism of two shapes of nanocrystals enables the Cr2O3-based sensor to realize highly sensitive detection of trace H2S gas. At 170 °C, Cr2O3-600 exhibits a high response of 42.8 to 100 ppm H2S gas, which is 3.45 times larger than that of Cr2O3-500 assembled from nanocylinders. Meanwhile, this sensor has a low detection limit of 1.0 ppb (S = 1.4), good selectivity, stability, and moisture resistance. These results show that the combination of nanosized cylinders/ellipsoids together with exposed (104) facet can effectively improve the sensing performance of the p-type Cr2O3 material. In addition, the Cr2O3-600 sensor shows satisfactory results for actual monitoring of the corruption process of fresh chicken.

New family of silver(I) complexes based on hydroxyl and carboxyl groups decorated arenesulfonic acid: syntheses, structures, and luminescent properties.

Self-assembly of silver(I) salts and three ortho-hydroxyl and carboxyl groups decorated arenesulfonic acids affords the formation of nine silver(I)-sulfonates, (NH(4))·[Ag(HL1)(NH(3))(H(2)O)] (1), {(NH(4))·[Ag(3)(HL1)(2)(NH(3))(H(2)O)]}(n) (2), [Ag(2)(HL1)(H(2)O)(2)](n) (3), [Ag(2)(HL2)(NH(3))(2)]·H(2)O (4), [Ag(H(2)L2)(H(2)O)](n) (5), [Ag(2)(HL2)](n) (6), [Ag(3)(L3)(NH(3))(3)](n) (7), [Ag(2)(HL3)](n) (8), and [Ag(6)(L3)(2)(H(2)O)(3)](n) (9) (H(3)L1 = 2-hydroxyl-3-carboxyl-5-bromobenzenesulfonic acid, H(3)L2 = 2-hydroxyl-4-carboxylbenzenesulfonic acid, H(3)L3 = 2-hydroxyl-5-carboxylbenzenesulfonic acid), which are characterized by elemental analysis, IR, TGA, PL, and single-crystal X-ray diffraction. Complex 1 is 3-D supramolecular network extended by [Ag(HL1)(NH(3))(H(2)O)](-) anions and NH(4)(+) cations. Complex 2 exhibits 3-D host-guest framework which encapsulates ammonium cations as guests. Complex 3 presents 2-D layer structure constructed from 1-D tape of sulfonate-bridged Ag1 dimers linked by [(Ag2)(2)(COO)(2)] binuclear units. Complex 4 exhibits 3-D hydrogen-bonding host-guest network which encapsulates water molecules as guests. Complex 5 shows 3-D hybrid framework constructed from organic linker bridged 1-D Ag-O-S chains while complex 6 is 3-D pillared layered framework with the inorganic substructure constructing from the Ag2 polyhedral chains interlinked by Ag1 dimers and sulfonate tetrahedra. The hybrid 3-D framework of complex 7 is formed by L3(-) trianions bridging short trisilver(I) sticks and silver(I) chains. Complex 8 also presents 3-D pillared layered framework, and the inorganic layer substructure is formed by the sulfonate tetrahedrons bridging [(Ag1O(4))(2)(Ag2O(5))(2)](∞) motifs. Complex 9 represents the first silver-based metal-polyhedral framework containing four kinds of coordination spheres with low coordination numbers. The structural diversities and evolutions can be attributed to the synthetic methods, different ligands and coordination modes of the three functional groups, that is, sulfonate, hydroxyl and carboxyl groups. The luminescent properties of the nine complexes have also been investigated at room temperature, especially, complex 1 presents excellent blue luminescence and can sensitize Tb(III) ion to exhibit characteristic green emission.

A rational design of layered metal-organic framework towards high-performance adsorption of hazardous organic dye.

Water pollution originating from organic dyes is endangering the survival and development of society; however, adsorbents with high capacity (>5000 mg g-1) for the fast removal (≤30 min) of Congo Red (CR) in aqueous solution have been not reported to date. In the present work, an acid-base stably layered MOF, [Cd(H2L)(BS)2]n·2nH2O (L-MOF-1, H2L = N1,N2-bis(pyridin-3-ylmethyl)ethane-1,2-diamine, BS = benzenesulfonate), was hydrothermally prepared. L-MOF-1 exhibited high-performance adsorption of CR in aqueous solution at room temperature. The experimental adsorption capacity of the L-MOF-1 adsorbent towards CR reached up to about 12 000 mg g-1 in 20 min in the pH range of 2.2-4.7, which is the best adsorbent with the highest capacity and fastest adsorption of CR to date. The spontaneous adsorption process can be described by the pseudo-second-order kinetic and Langmuir isotherm models. Meanwhile, the L-MOF-1 absorbent possessed a highly positive zeta potential in acid condition (even at pH = 2.2, zeta potential = 36.2 mV). Its good adsorption performance mainly originates from its strong electrostatic attraction with CR in acidic condition, together with diverse hydrogen bonds and ππ stacking interactions. Furthermore, the L-MOF-1 absorbent exhibited good selectivity and could be reused five times through simply washing, where its adsorption efficiency was hardly affected. Therefore, L-MOF-1 is a potential absorbent for effectively removing CR from dye wastewater.

Novel neuron-network-like Cu-MoO2/C composite derived from bimetallic organic framework for highly efficient detection of hydrogen peroxide.

Fabrication of non-enzymatic electrochemical sensors based on metal oxides with low valence-state for nanomolar detection of H2O2 has been a great challenge. In this work, a novel neuron-network-like Cu-MoO2/C hierarchical structure was simply prepared by in-situ pyrolysis of 3D bimetallic-organic framework [Cu(Mo2O7)L]n [L: N-(pyridin-3-ylmethyl)pyridine-2-amine] crystals. Meanwhile, the MoO2/C nano-aggregates were also obtained by liquid phase copper etching. Subsequently, two non-enzymatic electrochemical sensors were fabricated by simple drop-coating of the above two materials on the surface of glassy carbon electrode (GCE). Electrochemical measurements indicate that the Cu-MoO2/C/GCE possesses highly efficient electrocatalytic H2O2 property during wider linear range of 0.24 µM-3.27 mM. At room temperature, the Cu-MoO2/C composite displays higher sensitivity (233.4 µA mM-1 cm-2) and lower limit of detection (LOD = 85 nM), which are 1 and 2.5 times larger than those of MoO2/C material, respectively. Such excellent ability for trace H2O2 detection mainly originates from the synergism of neuron-network-like structure, enhanced electrical conductivity and increased active sites caused by low valence-state MoO2 and co-doping of Cu and carbon, and even the interaction between Cu and Mo. In addition, the H2O2 detection in spiked human serum and commercially real samples indicates that the Cu-MoO2/C/GCE sensor has certain potential application in the fields of environment and biology.

Coral-like CoMoO4 hierarchical structure uniformly encapsulated by graphene-like N-doped carbon network as an anode for high-performance lithium-ion batteries.

Encapsulation of metal oxide anode material with hierarchical structure in graphene-like high conductivity carbon network is conducive to improving the lithium storage performance of the anode material. However, it is very challenging to rational synthesizing anode materials with such structure. Herein, a mesoporous spiny coral-like CoMoO4 (SCL-CMO) self-assembled from the mesoporous nanorods made of nanoparticles is prepared by a simple one-step solvothermal method. The layered coral-like CoMoO4@N-doped Carbon (LCL-CMO@NC) composite is synthesized by polymerization of DA on the surface of SCL-CMO at room temperature and the subsequent sintering treatment. This LCL-CMO@NC composite perfectly combines the comprehensive advantages of the spiny coral-like hierarchical architecture and the N-doped graphene-like carbon coating, which not only effectively improve the electron and Li+ ion transport dynamics and accommodate the large volume changes, but also prevent hierarchical structure aggregation and pulverization during cycle process. Therefore, LCL-CMO@NC composite exhibits superior electrochemical kinetics and stability. The reversible specific capacity remained 1321.6 and 132 mA h g-1 after 900 and 10,000 cycles at 0.4 and 5 A g-1, respectively.

1,4-Bis(2-pyridylimino-meth-yl)benzene.

In the crystal structure of the title compound, C(18)H(14)N(4), the mol-ecule assumes site symmetry with the centroid of the benzene ring located on the inversion center. The mol-ecule is almost flat, with a dihedral angle of 2.70 (9)° between the pyridine and benzene rings.

Tetra-kis(2-amino-pyrazine-κN)dichlorido-cobalt(II).

The Co(II) atom in the title complex, [CoCl(2)(C(4)H(5)N(3))(4)], exists in an all-trans Cl(2)N(4)Co octa-hedral geometry. The Co(II) atom lies on a special position of 2 site symmetry. Adjacent mol-ecules are linked by N-H⋯N and N-H⋯Cl hydrogen bonds into a three-dimensional network.

Hexaaqua-cobalt(II) tetra-aqua-bis(2-amino-pyrazine-κN)cobalt(II) disulfate dihydrate.

The reaction of cobalt(II) sulfate and 2-amino-pyrazine affords the title salt, [Co(H(2)O)(6)][Co(C(4)H(5)N(3))(2)(H(2)O)(4)](SO(4))(2)·2H(2)O. The metal atoms in the tetra-aqua-coordinated and hexa-aqua-coordinated complex cations lie on centers of inversion in slightly distorted octa-hedral geometries. The cations, anions and solvent water mol-ecules are linked by O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds into a three-dimensional network.

Hexaaqua-manganese(II) tetra-aqua-bis(2-amino-pyrazine-κN)manganese(II) disulfate dihydrate.

The reaction of manganese(II) sulfate and 2-amino-pyrazine affords the title salt, [Mn(H(2)O)(6)][Mn(C(4)H(5)N(3))(2)(H(2)O)(4)](SO(4))(2)·2H(2)O. The metal atoms in the tetra-aqua-coordinated and hexa-aqua-coordinated cations lie on centers of inversion in octa-hedral geometries. The cations, anions and solvent water mol-ecules are linked by O-H⋯O, N-H⋯O and O-H⋯N hydrogen bonds into a three-dimensional network.

4-Hydroxy-pyridinium hydrogen sulfate.

The crystal structure of the title salt, C(5)H(6)NO(+)·HSO(4) (-), consists of planar(r.m.s. deviation = 0.001 Å) 4-hydroxy-pyridinium cations and hydrogen sulfate anions which are hydrogen bonded into a layer motif. In the anion, the S-O bond [1.551 (2) Å] involving the O atom bearing the acid H atom is longer than the other three S-O bonds, which range from 1.437 (1) to 1.454 (1) Å.

Cd(ii) coordination polymers constructed from bis(pyridyl) ligands with an asymmetric spacer in chelating mode and diverse organic dicarboxylates: syntheses, structural evolutions and properties.

Self-assembly of diverse Cd(ii) metal salts, four organic dicarboxylic acids, and two flexible bis(pyridyl) ligands leads to the formation of thirteen complexes, namely, [Cd(L1)(C4H4O4)]n (1), [Cd(L2)(C4H4O4)0.5]n·nOH·8nH2O (2), [Cd(L1)(C4H2O4)]n (3), [Cd(L1)(C4H2O4)]n (4), [Cd2(L2)(C4H2O4)2(H2O)2]n·nH2O (5), [Cd2(L1)(m-BDC)2(H2O)2]n (6), [Cd2(L2)(m-BDC)2(H2O)2]n (7), [Cd3(L1)2(p-BDC)3(H2O)4]n·2nH2O (8), [Cd(L2)(p-BDC)0.5Cl]n (9), [Cd(L2)(p-BDC)0.5(H2O)]n·n(ClO4)·nH2O (10), [Cd3(L2)2(p-BDC)(SO4)2(H2O)6]n·4nH2O (11), [Cd(L2)(p-BDC)]n·nH2O (12) and [Cd(L2)(p-BDC)]n·nMeOH (13) (L1 = N,N'-bis(pyridin-4-ylmethyl)propane-1,2-diamine, L2 = N,N'-bis(pyridin-3-ylmethyl)propane-1,2-diamine, m-BDC2- = m-benzene dicarboxylate dianion, p-BDC2- = p-benzene dicarboxylate dianion), which have been characterized by elemental analysis, IR, TG, PL, and powder and single-crystal X-ray diffraction. The influence of different Cd(ii) salts on the structure variations and properties has also been investigated. Complexes 1 and 3 present a (4,4) layer motif accomplished by the interconnection of adjacent Cd(ii) cations through L1 molecules and trans-conformational succinates or fumarates. In contrast, the cis-conformational succinates in complex 2 only afford the formation of a chain structure. The L1 and L2 molecules in complexes 4 and 5 adopt the same coordination and join adjacent Cd(ii) cations together with fumarates, giving rise to different 3D networks with vma and irl topologies. The same coordination mode of L1 and L2 in complexes 6-8 joins adjacent Cd(ii) cations together with aromatic dicarboxylates, leading to different (63)(65·8), 2-periodic (6·3) and (4·4) layer motifs. The L2 molecules in complexes 9-13 present different coordination modes and join adjacent Cd(ii) cations together with p-BDC2- dianions to form diverse (6·3) layer motifs, and different 3D networks with cds and eca topologies. Therefore, the diverse coordination modes of the bis(pyridyl) ligand and the feature of different organic dicarboxylate anions can effectively influence the topological structures of these complexes. Luminescence investigation reveals that the emission maximum of these complexes varies from 403 to 433 nm in the solid state at room temperature.

Enhanced H2S gas-sensing performance of Zn2SnO4 hierarchical quasi-microspheres constructed from nanosheets and octahedra.

Most of the reported ternary oxides based sensors have not been realized to detect ppb-level H2S till now. In this work, Zn2SnO4 hierarchical quasi-microspheres were prepared through a facile surfactant-free hydrothermal method followed by calcination in air atmosphere. The quasi-microspheres are composed of nanosheets with the thickness of 100 nm and octahedra with the average size of 0.63 µm, respectively. The sensor fabricated from such Zn2SnO4 hierarchical quasi-microspheres shows excellent selective response to H2S at 133 °C with the lowest detection limit of 1 ppb. The gas response exhibits good linear relationship in the concentration range of 1-1000 ppb. Such outstanding H2S sensing property might be attributed to its porous structure, the synergistic effect of the two typical building blocks and the surface adsorbed oxygen, and the possible sensing mechanism is also discussed.

Large-Scale Synthesis of Hierarchically Porous ZnO Hollow Tubule for Fast Response to ppb-Level H2S Gas.

Response and recovery time to toxic and inflammable hydrogen sulfide (H2S) gas are important indexes for metal oxide sensors in real-time environmental monitoring. However, large-scale production of ZnO-based sensing materials for fast response to ppb-level H2S has been rarely reported. In this work, hierarchically porous hexagonal ZnO hollow tubule was simply fabricated by zinc salt impregnation and subsequently calcination using absorbent cotton as the template. The influence of calcination temperature on the corresponding morphology and sensing properties is also explored. The hollow tubules calcined at 600 °C are constructed from abundant cross-linked nanoparticles (∼20 nm). Its Brunauer-Emmett-Teller surface area is 31 m2·g-1 and the meso- and macroporous sizes are centered at 35 and 115 nm, respectively. The sensor with a lower detection limit of 10 ppb exhibits a fast response speed of 29 s toward the 50 ppb H2S rather than those of the reported intrinsic and doped ZnO-based sensing materials. Furthermore, the sensor shows a wide linear range (10-1000 ppb), good reproducibility, and stability. Such excellent trace ppb-level H2S performances are mainly related to the inherent characteristics of hierarchically porous hollow tubular structure and the surface-adsorbed oxygen control type mechanism.

Bis{mu-(E)-2-[(2-pyridylamino)(2-pyridylimino)methyl]benzato}bis[acetatozinc(II)] tetrahydrate.

In the C(2)-symmetric dinuclear title complex, [Zn(2)(C(18)H(13)N(4)O(2))(2)(C(2)H(3)O(2))(2)] x 4 H(2)O, each Zn(II) ion is five-coordinated in a distorted trigonal bipyramidal fashion by one carboxylate O atom from one benzoate ligand, one imine N atom and two pyridyl N atoms from a second benzoate ligand, and one O atom from an acetate anion. The two Zn atoms are bridged by the two benzoate ligands, forming a dinuclear structure with a 14-membered macrocycle. Adjacent dinuclear units are further connected by extensive hydrogen bonds involving the solvent water molecules, giving a three-dimensional hydrogen-bonded framework. The framework can be regarded as an example of the four-connected node network of the PtS topology.

Aqua(4-hydroxy-benzoato-κO)(4-hydroxy-benzoato-κO,O')(1,10-phenanthroline-κN,N')zinc(II) monohydrate.

The Zn atom in the title compound, [Zn(C(7)H(5)O(3))(2)(C(12)H(8)N(2))(H(2)O)]·H(2)O, exists in a distorted cis-ZnN(2)O(4) octa-hedral coordination geometry. One of the 4-hydroxy-benzoate anions chelates in a bidentate manner whereas the other is monodentate. The complex mol-ecules are linked through the uncoordinated water mol-ecules into a hydrogen-bonded sheet structure.

Aqua-chloridobis(1,10-phenanthroline-κN,N')zinc(II) chloride N,N-dimethyl-formamide solvate.

The Zn atom in the title salt, [ZnCl(C(12)H(8)N(2))(2)(H(2)O)]Cl·C(3)H(7)NO, is chelated by two phenanthroline mol-ecules and is bonded to one chloride ion and one water mol-ecule, resulting in a ZnN(4)ClO octa-hedral coordination environment with the Cl and O atoms in a cis conformation. The cations and anions are linked by O-H⋯Cl hydrogen bonds across a center of inversion, forming a hydrogen-bonded dimeric association. The dimethyl-formamide solvent mol-ecule is disordered over two orientations in a 0.56 (1):0.44 (1) ratio.

Tetra-aqua-bis(4-formyl-benzoato-κO)cobalt(II) tetra-hydrate.

The Co(II) atom in the title compound, [Co(C(8)H(5)O(3))(2)(H(2)O)(4)]·4H(2)O, which exists in an all-trans octa-hedral coordination geometry, lies on a center of inversion. The coordinated and uncoordinated water mol-ecules engage in extensive hydrogen-bonding inter-actions, forming a three-dimensional hydrogen-bonded network.