Efficient hexane isomers separation in isoreticular bipyrazolate metal-organic frameworks: The role of pore functionalization

Hydrocarbons separation in petrochemical industries is a key,energy-consuming stage in the manufacture of high-quality added-value products—hence the need for more efficient materials and environmentally friendly methodologies to improve this process.In this context,we have studied the effect of metal-organic frameworks(MOFs)pore functionalization in hexane isomers separation,isolating the robust isoreticular zinc(ll)bipyrazolates Zn(BPZ),showing no pore decoration,Zn(Me₂BPZ),the pores of which are decorated with apolar methyl groups,and Zn(BPZ(NH₂)₂),the spacers of which possess polar Lewis-basic functions(H₂BPZ=1H,1'H-4,4'-bipyrazole;H₂Me₂BPZ=3,3'-dimethyl-1H,1'H-4,4'-bipyrazole;H₂BPZ(NH₂)₂=3,5-diamino-1H,1'H-4,4'-bipyrazole;DMF=dimethylformamide).After characterizing Zn(BPZ(NH₂)₂)as per its crystal structure and thermal behaviour,and all the three MOFs as per their textural properties,we investigated,from the experimental and computational points of view,the impact of the square one-dimensional channels decoration on the separation of the hexane isomers,demonstrating the relevance of pore constrictions in the resolution of the title alkanes mixture.     

Solid-state phase transformations toward a metal-organic framework of 7-connected Zn40 secondary building units

In the development of metal-organic frameworks(MOFs),secondary building units(SBUs)have been utilized as molecular modules for the construction of nanoporous materials with robust structures.Under solvothermal synthetic conditions,dynamic changes in the metal coordination environments and ligand coordination modes of SBUs determine the resultant product structures.Alternatively,MOF phases with new topologies can also be achieved by post-synthetic treatment of as-synthesized MOFs via the introduction of acidic or basic moieties that cause the simultaneous cleavage/reformation of coordination bonds in the solid state.In this sense,we studied the solid-state transformation of two ndc-based Zn-MOFs(ndc=1,4-naphthalene dicarboxylate)with different SBUs but the same pcu topology to another MOF with sev topology.One of the chosen MOFs with pcu nets is[Zn₂(ndc)₂(bpy)]_n(bpy=4,4,-bipyridine),(6C_bpy-MOF)consisting of a 6-connected pillared-paddlewheel SBU,and the other is IRMOF-7 composed of 6-connected Zn40(C 00)6 SBUs and ndc.Upon post-structural modification,these pcu MOFs were converted into the same MOF with sev topology constructed from the uncommon 7-connected Zri₄O(COO)₇SBU(7C-MOF).The appropriate post-synthetic conditions for the transformation of each SBUs were systematically examined.In addition,the effect of the pillar molecules in the pillared-paddlewheel MOFs on the topology conversion was studied in terms of the linker basicity,which determines the inertness during the solid-state phase transformation.This post-synthetic modification approach is expected to expand the available methods for designing and synthesizing MOFs with controlled topologies.     

Separation of hexane isomers by introducing“triangular-like and quadrilateral-like channels”in a bcu-type metal-organic framework

The separation of hexane isomers is of vital importance to produce high quality gasoline in the petrochemical industry.However,the similar vapor pressure and boiling point of hexane isomers bring great difficulties and challenges in the separation process.Sieving effect,which allowing smaller molecules pass through and preventing others,should be a powerful strategy to solve this problem by making good use of porous materials.Therefore,physical separation by metal-organic framework(MOF)materials appears and becomes a burgeoning separation technique in industry.Due to the weak interaction between hexane isomers with absorbents,it puts forward higher requirements for the accurate design of MOF materials with optimal pore system.To address this issue,a novel MOF[Zn₉(tba)₉(dabco)₃]·12DMA-6MeOH(abbreviation:Zn₉(tba)₉(dabco)₃;H₂tba=4-(1H-tetrazol-5-yl)-benzoic acid;dabco=1,4-diazabicyclo[2.2.2]octane;DMA=N,N-dimethylacetamide)with bcu network has been designed and synthesized by reticular chemistry strategy.Benefiting from the pre-designed topology and suitable linear ligand H₂tba and dabco,the structure of Zn₉(tba)₉(dabco)₃exhibits two types of channels with triangular-like and quadrilateral-like geometry.Zn₉(tba)₉(dabco)₃with appropriate channel size and shape displays potential selective adsorption capacity of vapor-phase hexane isomers through sieving effect.Moreover,outstanding gas adsorptive separation properties of Zn₉(tba)₉(dabco)₃could also be speculated by theoretical ideal adsorbed solution theory(IAST),suggesting Zn₉(tba)₉(dabco)₃can be regarded as a potential adsorbent material for purification natural gas_Breakthrough experiments show that Zn₉(tba)₉(dabco)₃is capable of discriminating all four hexane isomers at 298 K,and the corresponding research octane number(RON)of the eluted mixture closes to 95,which is higher than the standard for industrially refined hexane blends(about 83).We speculate that sieving effect and diffusion are a synergetic contributory factor in their elution dynamics,which may be ascribed to temperature-dependent interaction between pore aperture and each isomer.This work presents a typical example for design of efficient MOF absorbents by reticular chemistry strategy.     

Preparation and Characterization of Flower-like Cu2SnS3 Nanostructures by Solvothermal Route

Flower-like Cu₂SnS₃ nanostructures composed of nano-flakes were successfully synthesized by solvothermal technique at 180℃for 16 h.In the preparation process,CuCI₂·2H₂O,SnCl₂·2H₂O and thiourea were used as raw materials,and ethylene glycol were used as solvent.The results showed that the obtained product was pure phase Cu₂SnS₃.The average diameter of Cu₂SnS₃ flowers and the thickness of the nano-flakes were about 1—1.5μm and 10 nm,respectively.The influence of reaction time and solvents on the morphology,size and structure of the products was investigated by powder X-ray diffraction and fieldemission scan electron microscopy（FESEM）.The ultraviolet-visible absorption spectrum measurement indicated that the band gap of the sample was about 1.26 eV and could be applied to the absorbing layer of thin solar cell.The possible formation mechanism of flower-like Cu₂SnS₃ was also proposed and discussed.     

Structure characteristics and microwave dielectric properties of Pr2(Zr1-xTix)3(MoO4)9 solid solution ceramic with a stable temperature coefficient

Pr₂(Zr_1-xTi_x)₃(MoO₄)₉ (x = 0.1–1.0) ceramics were prepared via a conventional solid-state method, the dependence of crystal structure and bond characteristics on microwave dielectric properties was investigated systemically. The X-ray diffraction patterns indicated that the single-phase Pr₂Zr₃(MoO₄)₉structure was formed in all the specimens. As the Ti⁴⁺content increased, the l...     

High pressure responsive luminescence of flexible Eu~(3+) doped PVDF fibrous mats

Exploring lanthanide doped materials and their high-pressure optical properties is important from the perspective of designing pressure sensors, piezoelectric materials, scintillators, and optoelectronic devices, just to mention a few. Understanding the high-pressure optical properties of polymeric fibrous mats provides significant advantages in terms of flexibility, tunability, facile processability, and malleability. In this work, we have developed flexible polyvinylidene difluoride(PVDF) fibrous mats doped with an Eu³⁺ source of Eu(NO₃)₃·5H₂O(EN-PF) or Eu₂(SO₄)₃(ES-PF) by a Forcespinning■ method. Microstructural analysis of these two systems indicates that Eu(NO₃)₃·5H₂O and Eu₂(SO₄)₃ are homogeneously distributed and dispersed into the PVDF matrix. Fiber formation promotes a β-phase PVDF. Eu³⁺ doping increases the β-phase. Its fraction is larger for the ES-PF mats. To understand their high-pressure optical properties, their photoluminescence spectra have been taken at various pressures up to 58 GPa in a diamond anvil cell. High-pressure luminescence illustrates a clear change in asymmetry ratio, peak intensity, peak breadth, color coordinate, and color temperature of Eu³⁺ ions from both EN-PF and ES-PF with a different extent of changes. Specifically, Eu³⁺ ions in the ES-PF mats switch from asymmetric to symmetric environment as pressure increases. Those in the EN-PF mats present symmetric environment for all tested pressures. Both of the Eu³⁺ doped PVDF systems present irreversible changes. Therefore,the EN-PF fibrous mats present an opportunity to make pressure induced red-orange-yellow tunable phosphors for multifunctional applications.     

Water-based synthesis of nanoscale hierarchical metal-organic frameworks:Boosting adsorption and catalytic performanceOA

The combination of nano sizes, large pore sizes and green synthesis is recognized as one of the most crucial and challenging problems in constructing metal-organic frameworks(MOFs). Herein, a water-based strategy is proposed for the synthesis of nanoscale hierarchical MOFs(NH-MOFs) with high crystallinity and excellent stability.This approach allows the morphology and porosity of MOFs to be fine tuned, thereby enabling the nanoscale crystal generation and a well-defined hierarchical system. The ...     

Effect of sintering temperature on the chemical bonding,electronic structure and electrical transport properties of β-Ga1.9Fe0.1O3 compounds

A model system,which is based on iron(Fe)doped gallium oxide(Ga₂O₃)(Ga_1.9Fe_0.1O₃),has been considered to elucidate the combined effect of transition-metal ion doping and processing temperature on the chemistry,local structure and chemical bonding,and electrical transport properties of a wide band gap oxide(Ga₂O₃).The Ga_1.9Fe_0.1O₃ compounds were synthesized using standard high-temperature solid state reaction method.The effect of processing conditions in terms of different calcination and sintering environments on the structural and electrical properties of Ga_1.9Fe_0.1O₃ compounds is studied in detail.Structural characterization by Raman spectroscopy revealed that Ga_1.9Fe_0.1O₃ compounds exhibit monoclinic crystal symmetry,which is quite similar to the intrinsic parental crystal structure,though Fedoping induces lattice strain.Sintering temperature(T_sint)which was varied in the range of 900-1200℃,has significant impact on the structure,chemical bonding,and electrical properties of Ga_1.9Fe_0.1O₃ compounds.Raman spectroscopic measurements indicate the proper densification of the Ga_1.9Fe_0.1O₃ compounds achieved through complete Fe diffusion into the parent Ga₂O₃ lattice which is evident at the highest sintering temperature.The X-ray photoelectron spectroscopy validates the chemical states of the constituent elements in Ga_1.9Fe_0.1O₃ compounds.The electrical properties of Ga_1.9Fe_0.1O₃ fully controlled by T_sint,which governed the grain size and microstructural evolution.The temperature and frequency dependent electrical measurements demonstrated the salient features of the Fe doped Ga₂O₃ compounds.The activation energy determined from Arrhenius equation is 0.5 e V.The results demonstrate that control over structure,morphology,chemistry and electrical properties of the Ga_1.9Fe_0.1O₃ compounds can be achieved by optimizing T_sint.     

Double diamond structured bicontinuous mesoporous titania templated by a block copolymer for anode material of lithium-ion battery

Titania has received considerable attention as a promising anode material of Li-ion battery(LIB).Controlling the structure and morphology of titania nanostructures is crucial to govern their performance.Herein,we report a mesoporous titania scaffold with a bicontinuous shifted double diamond(SDD)structure for anode material of LIB.The titania scaffold was synthesized by the cooperative self-assembly of a block copolymer poly(ethylene oxide)-block-polystyrene template and titanium diisopropoxide bis(acetylacetonate)as the inorganic precursor in a mixture solvent of tetrahydrofuran and HCl/water.The structure shows tetragonal symmetry(space group I4₁/amd)comprising two sets of diamond networks adjoining each other with the unit cell parameter of a=90 nm and c=127 nm,which affords the porous titania a specific surface area(SSA)of 42 m²·g^-1with a mean pore diameter of 38 nm.Serving as an anode material of LIB,the bicontinuous titania scaffold exhibits a high specific capacity of 254 mAh·g^-1at the current density of 1 A·g^-1and an alluring self-improving feature upon charge/discharge over 1,000 cycles.This study overcomes the difficulty in building up ordered bicontinuous functional materials and demonstrates their potential in energy storage application.     

Effect of MWCNTs Additive on Desorption Properties of Zn（BH4）2 Composite Prepared by Mechanical Alloying

In this study,the effect of multi-walled carbon nanotubes（MWCNTs） additive on the dehydriding properties of the Zn（BH₄）₂/NaCI composite prepared by high energy ball milling were investigated.X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR） results demonstrated that Zn（BH₄）₂ was produced from mechanochemical reaction between ZnCI₂ and NaBH₄.Compared with the undoped sample,10 wt% MWCNTs effectively lowered the decomposition temperature of Zn（BH₄）₂ by 15℃.The complex released 3.6 wt%hydrogen within 250 s at 100℃and totally released 4.5 wt%hydrogen within 2500 s,indicating it has a considerable potential as a hydrogen storage material.     

From a mononuclear FeL2complex to a Fe4L4molecular square:Designed assembly and spin-crossover property

By introduction of a new Fe(L¹)₂spin-crossover(SCO)unit into the polynuclear system,a nano-scale Fe4(L²)₄molecular square architecture is designed through coordination-directed self-assembly strategy.Both the mononuclear Fe(L¹)₂and tetranuclear Fe4(L²)₄complexes have bee门structurally confirmed by 1H nuclear magnetic resonance(NMR),electrospray ionization time-of-flight mass spectrometry(ESI-TOF-MS),and temperature-dependent single crystal X-ray diffraction studies.Variable-temperature magnetic susceptibility measurements reveal the presence of an abrupt SCO behavior with a thermal hysteresis width of 4K for Fe(L¹)₂.By clear contrast,Fe4(L²)₄undergoes a gradual spin transition behavior with enlarged thermal hysteresis width and higher spin transition temperature.     

Intriguing anti-superbug Cu2O@ZrP hybrid nanosheet with enhanced antibacterial performance and weak cytotoxicity

In view of it’s strong antibacterial function and minor toxicity, cuprous oxide (Cu₂O) is frequently used in various broad-spectrum antibacterial reagents. Nonetheless the undesirable effects of superbugs still remain challenging. In this research, a chemical deposition approach is used to prepare a Cu₂O@ZrP composite with nanosheet configuration demonstrating excellent dispersibility and antibacterial traits. From systematic analysis, it was inffered that the content of copper in the nanosheet was about 57–188 mg/g while the average thickness of the nanosheets Cu₂O formed on ZrP is approximately 0.8 nm. The results of the minimal inhibitory concentration (MIC) revealed that an extremely low loading of Cu₂O in Cu₂O@ZrP nanosheet can lead to exceptional antibacterial activity. Examined on two various superbugs; i.e. methicillin-resistant staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus (VRE), the composite nanosheet reagent performed over 99% microbial reduction. More intesetingly, the cell growth rate of the Cu₂O@ZrP nanosheet was determined to be 20% lower than that of the neat Cu₂O, manifesting a weaker cytotoxicity. This unique hybrid nanosheet with intriguing anti-superbug performance promises highly efficient protection for the fabrics, battledress, and medical textiles.

     

Probing surface structure on two-dimensional metal-organic layers to understand suppressed interlayer packing

Two-dimensional metal-organic layers (MOLs) from alternatively connected benzene-tribenzoate ligands and Zr₆(μ₃-O)₄(μ₃-OH)₄ or Hf₆(μ₃-O)₄(μ₃-OH)₄ secondary building units can be prepared in gram scale via solvothermal synthesis. However, the reason why the monolayers did not pack to form thick crystals is unknown. Here we investigated the surface structure of the MOLs by a combination of sum-frequency generation spectroscopy, nanoscale infrared microscopy, atomic force microscopy, aberration-corrected transmission electron microscopy, and compositional analysis. We found a partial coverage of the monolayer surface by dangling tricarboxylate ligands, which prevent packing of the monolayers. This finding illustrates low-density surface modification as a strategy to prepare new two-dimensional materials with a high percentage of exposed surface.

     

Reticular exploration of uranium-based metal-organic frameworks with hexacarboxylate building units

The rational reticular design of metal-organic frameworks(MOFs)from building units of known geometries is essential for enriching the diversity of MOF structures.Unexpected and intriguing structures,however,can also arise from subtle changes in the rigidity/length of organic linkers and/or synthetic conditions.Herein,we report three uranium-based MOF structures—i.e.,NU-135X(X=0,1,2)—synthesized from trigonal planar uranyl nodes and triptycene-based hexacarboxylate ligands with variable arm lengths.A new chiral 3,6-connected nuc net was observed in NU-1350,while the extended versions of the ligand led to 3-fold catenated MOFs(NU-1351 and NU-1352)with rare 3,6-connected cml-c3 nets.The differences in the topology of NU-1350 and NU-1351/NU-1352 could be attributed to the slight distortions of the shorter linker in the former from the ideal trigonal prism geometry to an octahedral geometry when coordinated to the trigonal planar uranyl nodes.     

Highly luminescent and stable CsPbBr3 perovskite quantum dots modified by phosphine ligands

All-inorganic cesium lead halide perovskite quantum dots (QDs) have been a promising candidate for optoelectronic devices in recent years, such as light-emitting diodes, photodetectors and solar cells, owing to their superb optoelectronic properties. Still, the stability issue of nanocrystals is a bottleneck for their practical application. Herein, we report a facile method for the synthesis of a series of phosphine ligand modified CsPbBr₃ QDs with high PL intensity. By introducing organic phosphine ligands, the tolerance of CsPbBr₃ QDs to ethanol, water and UV light was dramatically improved. Moreover, the phosphine ligand modified QD films deposited on the glass subtracts exhibit superior PL intensity and optical stability to those of pristine QD based films.

     

Doping modulated in-plane anisotropic Raman enhancement on layered ReS2

Anisotropic two-dimensional (2D) materials exhibit lattice-orientation dependent optical and electrical properties. Carriers doping of such materials has been used to modulate their energy band structures for opto-electronic applications. Herein, we show that by stacking monolayer rhenium disulfide (ReS₂) on a flat gold film, the electrons doping in ReS₂ can affect the in-plane anisotropic Raman enhancement of molecules adsorbed on ReS₂. The change of enhancement factor and the degree of anisotropy in enhancement with layer number are sensitively dependent on the doping level of ReS₂ by gold, which is further confirmed by Kelvin probe force microscopy (KPFM) measurements. These findings could open an avenue for probing anisotropic electronic interactions between molecules and 2D materials with low symmetry using Raman enhancement effect.

     

Novel hollow Ni0.33Co0.67Se nanoprisms for high capacity lithium storage

In this work, homogeneous Ni_0.33Co_0.67Se hollow nanoprisms were synthesized successfully in virtue of Kirkendall effect. It is the first time for bimetallic Ni-Co compounds Ni_0.33Co_0.67Se to be used in lithium-ion batteries (LIBs). Impressively, the Ni_0.33Co_0.67Se hollow nanoprisms show superior specific capacity (1,575 mAh/g at the current density of 100 mA/g) and outstanding rate performance (850 mAh/g at 2,000 mA/g) as anode material for LIBs. This work proves the potential of bimetallic chalcogenide compounds as high performance anode materials for LIBs.

     

Panorama of boron nitride nanostructures via lamp ablation

A diverse range of remarkable boron nitride (BN) nanostructures subsuming nano-horns, nano-rods, nano-platelets, and clusters of hollow nanospheres (nano-onions, arguably of greatest applied and fundamental interest) have been produced exclusively from crystalline BN precursor powder via lamp ablation. The procedure is safe, devoid of toxic reagents, simple, rapid and scalable—generating some genres of nanoparticles that had previously proved elusive. Product structure and composition were unambiguously assessed by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy.

     

Blinking CsPbBr3 perovskite nanocrystals for the nanoscopic imaging of electrospun nanofibers

Blinking fluorophore perovskite nanocrystals (NCs) were employed to image the fine structure of the polystyrene (PS) electrospun fibers. The conditions of CsPbBr3 NCs embedded and dispersed into PS were investigated and optimized. The stochastic optical reconstruction microscopy is employed to visualize the fine structure of the resulted CsPbBr3@PS electrospun fibers at sub-diffraction limit. The determined resolution in the reconstructed nanoscopic image is around 25.5 nm, which is much narrower than that of conventional fluorescence image. The complex reticulation and multicompartment in bead sub-diffraction-limited structures of CsPbBr3@PS electrospun fibers were successfully mapped with the help of the stochastic blinking properties of CsPbBr3 NCs. This work demonstrated the potential applications of CsPbBr3 perovskite NCs in super-resolution fluorescence imaging to reconstruct the sub-diffraction-limited features of polymeric material.     

Hybrids of gold nanoparticles and oligo(p-phenyleneethynylene)s end-functionalized with alkynylruthenium groups: Outstanding two-photon absorption in the second biological window

Oligo(p-phenyleneethynylene)s (OPEs) end-capped with (alkynyl)bis(diphosphine)ruthenium and thiol/thiolate groups stabilize ca. 2 nm diameter gold nanoparticles (AuNPs). The morphology, elemental composition and stability of the resultant organometallic OPE/AuNP hybrid materials have been defined using a combination of molecular- and nano-material chacterization techniques. The hybrids display long-term stability in solution (more than a month), good solubility in organic solvents, reversible ruthenium-centered oxidation, and transparency beyond 800 nm, and possess very strong nonlinear absorption activity at the first biological window, and unprecedented two-photon absorption activity in the second biological window (σ₂ up to 38,000 GM at 1,050 nm).