Hydrothermal Synthesis of MoO_2 and Supported MoO_2 Catalysts for Oxidative Desulfurization of Dibenzothiophene

A novel method for obtaining spherical MoO2 nanoparticles and SiO2-Al2O3 supported MoO2 by hydrothermal reduction of Mo(VI) species was studied. The obtained MoO2 catalysts show very high catalytic activity in the oxidative desulfurization(ODS) process. The effect of hydrothermal temperature and crystallization temperature on ODS activity was investigated. The ODS activity of supported MoO2 catalysts with various MoO2 contents were also investigated. The mechanism for formation of MoO2 involving oxalic acid was proposed.

Solvothermal Synthesis of V_2O_3 Catalysts for Oxidative Desulfurization of Dibenzothiophene

V2O3 nanoparticles with high surface area have been successfully prepared by a new solvothermal method without using any surfactant and template. The size of V2O3 nanoparticles is mostly equal to 10 nm-30 nm. The highest surface area of obtained V2O3 nanoparticles reaches 49 m2/g. Several kinds of V2O3 catalysts were prepared by different methods. All these V2O3 catalysts obtained thereby showed high catalytic activity for oxidative desulfurization(ODS) reaction by using tert-butyl hydroperoxide as the oxidant. The V2O3 catalyst with a highest ODS activity was obtained under the following conditions: The catalyst was prepared upon using V2O5 as the vanadium source, methanol as the solvent, and oxalic acid as the complexing reagent at a V2O5/oxalic acid molar ratio of 1:2. The process for ODS of dibenzothiophene was carried out under mild conditions(under atmospheric pressure and at a relatively low temperature). The highest ODS activity of the obtained V2O3 nanoparticles can be attributed to their highest surface area.

High specific surface area porous graphene grids carbon as anode materials for sodium ion batteries

Although great accomplishments of functional material synthesis have been achieved in sodium ion batteries(SIBs)recently,there are still numerous challenges and problems in preparing carbon-based materials with porous architectures and enough lattice distance for Na^+insertion.Herein we report a templated strategy to synthesize 3D porous graphene girds(PGGs)consisting of several stacking graphene structure with ultrahigh surface area and hierarchical connected structure by employing Ag nanoparticles(NPs).The Ag NPs will regenerate for decreasing the experimental cost,also in line with principles of green chemistry and environmentally friendly strategy.The PGGs obtain advanced specific capacity of160 m A h g^(-1)at current density of 50 m A h g^(-1).Moreover,112 mA h g^(-1)capacity can be gained at 1 A h g^(-1)during 1000 cycles.Due to their porous architecture,ultrahigh surface area and low amorphous graphited structure,PGGs electrode showed the excellent electrochemical performance in high rate capability.

Dehydrogenation characteristics of LiAlH4 improved by in-situ formed catalysts

The hydrogen storage properties and catalytic mechanism of FeCl-doped LiAlHwere investigated in minute details. LiAlH-2 mol% FeClsamples start to release hydrogen at 76 °C, which is 64 °C lower than that of as-received LiAlH. Isothermal desorption measurements show that the 2 mol% FeCl-doped sample releases 7.0 wt% of hydrogen within 17 min at 250 °C. At lower temperatures of 110 °C and 80 °C, the sample can release 4.4 wt% and 3 wt% of hydrogen, respectively. The apparent activation energy of LiAlH-2 mol% FeClsamples for R2 is 105.02 k J/mol, which is 67 k J/mol lower than that of pure LiAlH. The reaction between LiAlHand FeClduring ball milling was found by analyzing the X-ray diffraction results,and Fe-Al particles formed in-situ from the reaction act as the real catalyst for the dehydrogenation of LiAlH.

Novel application of LiCoO_2 as a high-performance candidate material for supercapacitor

Electrochemical performances of LiCoO_2 as a candidate material for supercapacitor are systematically investigated. LiCoO_2 nanomaterials are synthesized via hydrothermal reaction with consequent calcination process. And the particle size increases as the calcination temperature rises. LCO-650 sample with the largest particle size displays the maximum capacitances of 817.5 F·g^-1 with the most outstanding capacity retention rate of 96.8% after 2000 cycles. It is shown that large particle size is beneficial to the electrochemical and structural stability of LiCoO_2 materials. We speculate that the micron-sized waste LiCoO_2 materials have great potential for supercapacitor application. It may provide a novel recovered approach for spent LIBs and effectively relieve the burdens on the resource waste and environment pollution.

Synergetic effects of NaAlH_4-TiF_3 co-additive on dehydriding reaction of Mg(AlH_4)_2

The effects of NaA1H4, TiF3 and NaA1H4-TiF3 co-additive on dehydriding reaction of Mg（A1H4）2 are systematically investigated. The on- set dehydrogenation temperature of the co-doped Mg（A1H4）2 composites decreased to 74 ℃, which is about 59 ℃ lower than that of pure Mg（A1H4）2. The dehydrogenation kinetics of NaA1H4-TiF3 co-doped Mg（A1H4）2 sample was also improved, which released about 94% hydrogen within 48 min, but no visible hydrogen was released from pure Mg（A1H4）2 under the same conditions. The activation energy of co-doped Mg（A1H4）2 was 85.6 kJ.mol-t, which was significantly lower than that of additive-free Mg（A1H4）2 sample. The synergetic effects of NaA1H4 and TiF3 on the dehydrogenation performance of Mg（A1H4）2 were confirmed. In addition, a possible catalytic mechanism is discussed, regarding the different roles of NaA1H4 and TiF3 on Mg（A1H4）2.

Preparation of porous α-Fe_2O_3-supported Pt and its sensing performance to volatile organic compounds

Porous α-Fe2O3 was synthesized by a simple hydrothermal treatment of FeC13 aqueous solution followed by a calcination process. In the synthesis of porous α-Fe2O3, no templates or pore-directing agents were used. The as-prepared porous α-Fe2O3 was further employed as a support for loading Pt nanoparticles. The gas sensing performance of the obtained porous α-Fe2O3-supported Pt to VOCs was investigated. The sensor presented a high response and fast response-recovery characteristic to several VOCs including acetone, ether, methanol, ethanol, butanol and hexanol. Meanwhile, it exhibited a much higher response than the pure α-Fe2O3 at the operating temperature of 260 ℃. The enhanced sensing properties may be related to the unique porous structure of the α-Fe2O3 support and the promoting effect of active Pt nanoparticles for the sensing reactions.

Syntheses,Crystal Structures and Magnetic Properties of Two Nitrophenyl Substituted Nitronyl Nitroxide Radical-lanthanide Complexes

Syntheses, structures and magnetic properties of two nitrophenyl substituted nitronyl nitroxide radical-lanthanide complexes [Ln（hfac）3（NITmNO2）2] （Ln = Sm（Ⅲ） （1）, Tb（Ⅲ） （2）, hfac = hexafluoroacetylacetonate, NITmNO2 = 2-（3-nitrophenyl）-4,4,5,5-tetramethyl-imidazo- line-1-oxyl-3-oxide） have been described in this paper. X-ray analysis shows that the two complexes have similar mononuclear trispin radical-Ln（Ⅲ）-radical structures, in which the central Ln（Ⅲ） ions are all eight coordinated in D2d dodecahedral （DD） geometry formed by six oxygen atoms from three hfac and two oxygen atoms from nitronyl nitroxide. The magnetic study indicates the antiferromagnetic interaction between Sm（Ⅲ） ion and NITmNO2 in complex 1, while weak ferromagnetic interaction between Tb（Ⅲ） ion and NITmNO2 in complex 2.

Manipulation of π-aromatic conjugation in two-dimensional Sn-organic materials for efficient lithium storage

Sn-based materials are promising candidates for lithium storage but suffer generally from huge volume change during the(de)lithiation processes.Sn-organic materials with monodispersed Sn centers surrounded by lithium active ligands can alleviate the volume change of anode materials based on reversible(de)lithiation processes.However,the structural factors governing the kinetics of lithium storage and utilization efficiency of active sites are not well understood to date.Herein,we report three two-dimensional Sn-organic materials with enhanced lithium storage performance by manipulation ofπ-aromatic conjugation of the ligands.The increasingπ-aromatic conjugation plays a key role in promoting efficient lithium storage,and the volume expansion during the(de)lithiation reaction is suppressed in these Sn-organic materials.This work reveals that theπ-aromatic conjugation of the ligand is crucial for improving the kinetics of lithium storage and the utilization of active sites in metalorganic materials with minimised volume expansion.

Rapid detection of nanoplastic particles by a luminescent Tb-based coordination polymer

Nanoplastics(NPs)in aqueous environment have become a category of emerging pollutants on account of their potential risks to both human health and environment.The detection of NPs is a great challenge due to the lack of sensitive and selective sensing materials with fast response time and wide sensing range of particle sizes.Herein,a Tb-based coordination polymer has been synthesized for luminescent detection of nanopolystyrene with different particle sizes in aqueous solutions,showing a low limit of detection,fast response time within 10 s and high selectivity in the presence of other plastics.The“turn-on”sensing mechanism is studied in detail.This work provides a facile method for the fast detection of NPs.

Two-dimensional bimetallic coordination polymers as bifunctional evolved electrocatalysts for enhanced oxygen evolution reaction and urea oxidation reaction

Two-dimensional coordination polymers(CPs) have aroused tremendous interest as electrocatalysts because the catalytic performance could be fine-tuned by their well-designed coordination layers with highly accessible and active metal sites.However,it remains great challenge for CP-based catalysts to be utilized for electrocatalytic oxidation reactions due to their inefficient activities and low catalytic stabilities.Herein,we applied a mixed-metal strategy to fabricate two-dimensional Co_xNi_(1-x)-CPs with dual active sites for electrocatalytic water and urea oxidation.By metal ratio regulation in the twodimensional layer,an optimized Co_(2/3)Ni_(1/3)-CP exhibits a water oxidation performance with an overpotential of 325 mV at a current density of 10 mA cm^(-2) and a Tafel slope of 86 mV dec^(-1) in alkaline solution for oxygen evolution reaction.Importantly,a lower potential than that of commercial RuO_(2) is observed over20 mA cm^(-2).Co_(2/3)Ni_(1/3)-CP also displays a potential of 1.381 V at 10 mA cm^(-2) for urea oxidation reaction and a Tafel slope of 124 mV dec^(-1).This mixed-metal strategy to maximize synergistic effect of different metal centers may ultimately lead to promising electrocatalysts for small molecule oxidation reaction.

Two monofluoride-bridged Dy~Ⅲdimers with different magnetization dynamics

As a monoatomic bridge,fluoride ion can transmit efficient magnetic interaction between lanthanide ions but its effect on tuning the magnetization dynamics has not been well understood.Herein,two monofluoride-bridged dinuclear dysprosium complexes[Dy_(2)F(bbpen)_(2)(Et OH)_(2)]Br·Et OH(1)and[Dy_(2)F(bbppy)_(2)]Br·2Et OH(2)with Dy-F-Dy angles of~178°and their diamagnetic-ion diluted analogues 1'and 2'were synthesized.Magnetic studies reveal that 1 and 1'barely show any magnetization dynamics,but 2 and 2'exhibit strong magnetization dynamics.Systematical experimental analysis combined with ab initio calculations reveals that the different magnetization dynamics between 1 and 2 mainly originate from the effect of magnetic anisotropy by terminal ligand and bridging group of the chelating ligand,and the fluoride bridge can effectively suppress the quantum tunneling of the magnetization and turn on Orbach process in 2.

Dynamic-static coupled sensing of trace biomarkers by molecularly imprinted metal-organic frameworks

Accommodating target analytes within the pores of metal-organic frameworks(MOFs)to improve the sensing performance is an important but challenging task.Here,we report a novel molecular imprinting strategy to create target recognition sites in a tailored multicomponent MOF with the inter-ligand synergistic antenna effect to lanthanide ions,enabling selective recognition of trace biomarkers,which is critical to the early diagnosis of age-related diseases in blood samples with high sensitivity and ultralow limit of detection(LOD)of 69 nmol L^(-1).Compared with MOF-based sensors without imprinted recognition sites,the significantly enhanced sensing performance(both sensitivity and LOD)was attributed to a dynamic-static coupled sensing mechanism:the dynamic interactions involve concentrating the trace biomarkers at the imprinted recognition sites to enhance the sensing performance at ultralow concentration,and the static interactions are derived from electron/energy exchange between the molecularly imprinted MOF and the biomarker to govern the sensing performance.This work establishes a new molecular imprinting strategy to attain advanced materials for sensing trace bio-analytes.

Direct synthesis and dehydrogenation properties of NaAlH_4 catalyzed with ball-milled Ti–B

Ball-milled Ti-B-doped sodium aluminum hydride was directly synthesized via mechanical ball-milling of a NaH/Al mixture. The mixture was completely hydrogenated to NaAlH4 after 70 h under hydrogen pressure of 1 MPa. And higher hydrogen pressure is beneficial for the conversion from NaH/Al mixture to NaAlH4. The dehydrogenation properties of the as-synthesized Ti-Bdoped sodium aluminum were systematically investigated.The result shows that ball-milled Ti-B has a remarkable catalytic effect on the enhanced dehydrogenation properties of NaAlH4. As-synthesized Ti-B-doped NaAlH_4 sample releases hydrogen at the temperature of about 100 ℃. Approximately 4.15 wt% H2 is released from ballmilled Ti-B-doped NaAlH_4 at 233.7 ℃. Even at 110 ℃, it also releases about 2.83 wt% hydrogen. The apparent activation energy（E_a） for the first step is estimated to be 83.97 k J·mol^-1 using Arrhenius equation. Thus, utilization of ball-milled Ti-B as catalyst would substantially enhance the practical applications of NaAlH_4 for hydrogen storage.

Synthesis,structure and magnetic properties of manganese(Ⅱ)coordination polymer with azido and zwitterionic dicarboxylate ligand

A coordination polymer formulated as {[Mn2L（N3）4]·2H2O）n（1） [L = 1,4-bis（pyridinil-3-carboxylato）-1,4- dimethylbenzene] was synthesized and structurally and magnetically characterized. The uniform Mn（Ⅱ） chains with mixed （μ-EO-N3）2（μ-COO） triple bridges （EO = end-on） are linked by L ligands to generate a 2-fold interpenetrating 3D framework. Meanwhile, magnetism analysis reveals antiferromagnetic coupling for 1.

Mixed Rare-Earth Complexes of Eu（Ⅲ） and Y（Ⅲ） with Pyridine-2,4,6-tricarboxylic Acid and Their Photoluminescent Properties

A series of rare-earth luminescent complexes {[Eu（pta）（H2O）3]·H2O}n（1, H3pta=pyridine-2,4,6-tricarboxylic acid） and {[EuxY（1-x）（pta）（H2O）3]·H2O}n（2-10） have been synthesized. Complexes 1 and 8 were determined by single-crystal X-ray diffraction, while other complexes were characterized by powder X-ray diffraction, displaying the similar structural mode. The luminescent properties of complexes 1--10 were investigated and the results show that the emission intensities of mixed rare-earth complexes 2--10 are the same or even higher than that of homometallic complex 1 with the increasing Y（Ⅲ） ions.

Facile synthesis of coordination polymer nanocubes and their conversion into mesoporous single crystal-like Y_2O_3 nanocubes

Mesoporous single crystal-like Y2O3 nanocubes have been prepared through a coordination-based self- assembly process. Firstly, a uniform nanocube-like Y-lysine precursor was simply prepared with hydrothermal treatment. After the simple thermal treatment process, nanocube-shaped yttrium oxides with the morphology inherited from the Y-lysine precursor were successfully prepared. The phase, morphology, size and crystalline structure were well characterized by XRD, SEM and TEM. N2 adsorption-desorption demonstrates the mesoporous characteristics of the Y2O3 nanocubes, showing a relatively high surface area of 60 m^2/g.

Syntheses,crystal structures and magnetic properties of three lanthanide-nitronyl nitroxide complexes

Three new lanthanide-nitronyl nitroxide radical complexes were successfully synthesized with the formula of [Ln（hfac）3（PyNONIT）2]（Ln=Dy（1）, Tm（2）, Ho（3））. All the complexes were isostructural and crystallized in C2/c space group, in which the central metal ions were eight-coordinated in slightly distorted square antiprism coordination geometries（D4d symmetry）. Magnetic studies indicated the existence of antiferromagnetic interaction in complexes 1–3.

Ni–B-doped NaAlH_4 hydrogen storage materials prepared by a facile two-step synthesis method

By directly introducing Ni–B into NaAlH4 system using a facile two-step synthesis method, the effects of Ni–B on NaAlH4 were systematically investigated. NaAlH4 can be completely formed after 30 h milling under 1 MPa hydrogen pressure. In addition, the dehydrogenation kinetics of as-prepared NaAlH4 after different milling times were investigated. As the dehydrogenation temperature rises,both the hydrogen desorption capacity and dehydrogenation rate quickly increase. The apparent activation energy E a for Ni–B-doped NaAlH4 is calculated to be 61.91 k J mol-1 for the first dehydrogenation step. More importantly, the dehydrogenation temperature of as-prepared NaAlH4 nanocrystalline can be reduced to about 100 °C.