Synthesis, Crystal Structure, Magnetic Property and DFT Study of a Novel 2D Polymer [Cu(pdc)(bpy)]·H_2O

A new copper complex [Cu（pdc）（bpy）]·H2 O（1, H2 pdc = 3,5-pyridinedicarboxylic acid, bpy = 2,2-bipyridine） has been solvothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, UV-vis spectroscopy and magnetic measure- ments. Complex 1 crystallizes in monoclinic system, space group P21 /c, a = 10.893（2）, b = 7.3641（15）, c = 1.9921（4）, β = 92.16（3）, V = 1596.9（6）3, Dc = 1.676 g/cm3, Mr = 402.84, Z = 4, F（000） = 820, μ = 1.404 mm-1, the final R = 0.0237 and wR = 0.0693. The Cu（II） ion is five-coordinated by two O atoms from two pdc ligands, one N atom from another pdc ligand and two N atoms from the bpy ligand. The pdc anion, which acts as a tridentate ligand, links three Cu ions, forming（3,3）-connected two-dimensional（2D） sheets. We also studied the electronic structure and orbital energies of complex 1 by DFT methods, and the results are consistent with UV-vis spectrum.

Weak Interactions and 2D Layer Structure of a New Ion-pair Complex Bis(1-benzyl-4-methylquinolinium)-bis(maleonitriledithiolato)nickel(Ⅱ)

A new ion-pair complex, [BzMeQ1]2[Ni（nmt）2]1（[BzMeQ1]^＋ = 1-benzyl-4-ntethylquino- linium, mnta- -- maleonitriledithiolate） has been synthesized and structurally characterized by IR, ESI-MS and X-ray diffraction methods. Complex 1 is of triclinic, space group PI, with a = 9.079（2）, b = 10.154（2）, c = 11.243（2）A, α= 81.58（1）, β= 69.63（1）, γ = 68.02（1）°, V= 940.1（3）A3, Dc = 1.427 g/cm^3, Z = 1, F（000） = 418 and R = 0.0442. A 2D layer structure is formed via the cation-cation π…π and C-H…π interactions observed in the solid state of the complex.

The Problem of Quasiperiodic Photonic Structures Solved by Considering the Cut of 2D Periodic Structure

The physical objective of solving for eigen-modes of a 1D quasiperiodic structure in photonics has been achieved. This was achieved thru considering this structure as a 1D projection or cut of a 2D periodic structure. And the problem is solved in a manner similar to 2D periodic photonic structures. A mechanical analogy (quasiperiodic orbits) helps to bring conceptual clarity.

A 2D Layered Thiostannate: Synthesis and Crystal Structure of [tmdpH_2]Sn_3S_7

A new thiostannate,[tmdpH2]Sn3S7 1（tmdp = 4,4＇-trimethylenedipiperidine）,has been synthesized under solvothermal conditions and characterized by elemental analysis,IR spectroscopy,and single-crystal X-ray diffraction analysis.In 1,the Sn3S4 secondary incomplete cubane-like building units are bridged by μ2-S atoms to form Sn12S12 rings which are then joined parallelly to the [001] plane,giving the final 2D（Sn3S7^2-）n layer of（6,3） network.The layers are stacked along the c axis so that 24-membered ring channels are generated,in which the organic cations are accommodated.The compound crystallizes in monoclinic,space group C2/c,with a=23.052（3）,b=13.4039（12）,c=18.412（2）A,β=120.112（4）°,V=4921.3（9）A^3,C13H28N2S7Sn3,Mr=792.86,Z=8,Dc=2.140 g/cm^3,F（000）=3056,μ=3.619 mm^-1,the final R=0.0488 and wR=0.1125 for 4607 observed reflections with I〉2σ（I）.

Construction of Ultrathin Layered MXene-TiN Heterostructure Enabling Favorable Catalytic Ability for High-Areal-Capacity Lithium-Sulfur Batteries

Catalysis has been regarded as an effective strategy to mitigate sluggish reaction kinetics and serious shuttle effect of Li-S batteries.Herein,a spherical structure consists of ultrathin layered Ti_(3)C_(2)T_(x)-TiN heterostructures(MX-TiN)through in-situ nitridation method is reported.Through controllable nitridation,highly conductive TiN layer grew on the surface and close coupled with interior MXene to form unique 2D heterostructures.The ultrathin heterostructure with only several nanometers in thickness enables outstanding ability to shorten electrons diffusion distance during electrochemical reactions and enlarge active surface with abundant adsorptive and catalytic sites.Moreover,the(001)surface of TiN is dominated by metallic Ti-3d states,which ensures fast transmitting electrons from high conductive MX-TiN matrix and thus guarantees efficient catalytic performance.Calculations and experiments demonstrate that polysulfides are strongly immobilized on MX-TiN,meanwhile the bidirectional reaction kinetics are catalytically enhanced by reducing the conversion barrier between liquid LiPSs and solid Li_(2)S_(2)/Li_(2)S.As a result,the S/MX-TiN cathode achieves excellent long-term cyclability with extremely low-capacity fading rate of 0.022%over 1000 cycles and remarkable areal capacity of 8.27 mAh cm^(−2) at high sulfur loading and lean electrolytes.

Nanocarbon-Enhanced 2D Photoelectrodes:A New Paradigm in Photoelectrochemical Water Splitting

Solar-driven photoelectrochemical(PEC)water splitting systems are highly promising for converting solar energy into clean and sustainable chemical energy.In such PEC systems,an integrated photoelectrode incorporates a light harvester for absorbing solar energy,an interlayer for transporting photogenerated charge carriers,and a co-catalyst for triggering redox reactions.Thus,understanding the correlations between the intrinsic structural properties and functions of the photoelectrodes is crucial.Here we critically examine various 2D layered photoanodes/photocathodes,including graphitic carbon nitrides,transition metal dichalcogenides,layered double hydroxides,layered bismuth oxyhalide nanosheets,and MXenes,combined with advanced nanocarbons(carbon dots,carbon nanotubes,graphene,and graphdiyne)as co-catalysts to assemble integrated photoelectrodes for oxygen evolution/hydrogen evolution reactions.The fundamental principles of PEC water splitting and physicochemical properties of photoelectrodes and the associated catalytic reactions are analyzed.Elaborate strategies for the assembly of 2D photoelectrodes with nanocarbons to enhance the PEC performances are introduced.The mechanisms of interplay of 2D photoelectrodes and nanocarbon co-catalysts are further discussed.The challenges and opportunities in the field are identified to guide future research for maximizing the conversion efficiency of PEC water splitting.

Syntheses, Crystal Structures and Properties of Two Metal-organic Complexes Based on 5-(4-Pyridyl)-methoxyl Isophthalic Acid

Two new metal-organic frameworks, [Co3L2（NO2）2（H2O）2],, （1） and{[Ni（L）（H2O）5] （H2O）2.DMF}, （2, H2L = 5-（4-pyridyl）-methoxyl isophthalic acid）, have been synthesized by the hydrothermal method and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis （TGA） and X-ray crystallography. Compound 1 crystallizes in the monoclinic system with space group P2/c and adopts a slightly distorted octahedral configuration. In compound 1, the 2D bilayered structures are linked by O-H...O and O-H...N hydrogen bonds to form a 3D framework. Compound 2 crystallizes in the monoclinic system with space group P2/n, and the central nickel atoms are octa-coordinated with five O atoms from coordinated water molecules and one N atom from one H2L ligand. The abundant O-H…O hydrogen bonds and π…π interactions link the molecules into a 3D framework. In addition, compounds 1 and 2 exhibit strong ultraviolet absorption in the solid state at room temperature.

Electronic structure of silicene

In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene. The interest in silicene is the same as for graphene, in being two-dimensional and possessing a Dirac cone. One advantage of silicene is due to its compatibility with current silicon electronics. Both empirical and first-principles techniques have been used to study the electronic properties of silicene. We will provide a brief overview of the parameter space for first-principles calculations.However, since the theory is standard, no extensive discussion will be included. Instead, we will emphasize what empirical methods can provide to such investigations and the current state of these theories. Finally, we will review the properties computed using both types of theories for free-standing silicene, with emphasis on areas where we have contributed.Comparisons to graphene is provided throughout.

Synthesis, Crystal Structure, Fluorescent Property and DFT Study of a Novel 1D Polymer [Zn(HMICD)(bpy)]_n·2nH_2O

A new one-dimensional（1D） polymer, [Zn（HMIDC）（bpy）]n·2n H2O（1, H3MIDC = 2-methyl-imidazole-4,5-dicarboxylic acid, bpy = 2,2-bipyridine）, has been solvothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy, UV-vis spectrum and fluorescence measurements. Complex 1 crystallizes in orthorhombic system, space group Pbca with a = 14.404（3）, b = 8.6900（17）, c = 26.570（5） , V = 3325.8（11） -3, Dc = 1.700 g/cm-3, Mr = 425.70, Z = 8, F（000） = 1744, μ = 1.522 mm-（-1）, the final R = 0.0421 and w R = 0.1018. The Zn（Ⅱ） ion is six-coordinated by O and N atoms from one HMIDC ligand, two O atoms from another HMIDC ligand and two N atoms from the bpy ligand. The HMIDC anion, which acts as a tetradentate ligand, chelates two Zn ions to form a one-dimensional（1D） zigzag chain structure. We analyzed the electronic structure and orbital energies of complex 1 by DFT methods, and the results are consistent with the UV-vis spectrum. And we also discussed the luminescent mechanism of complex 1 in detail.

Synthesis and Crystal Structure of 1,4-Bis-(benztriazol-1-ylmethyl)-2,3,5,6-tetramethylbenzene

The title compound 1,4-bis(benztriazol-1-ylmethyl)-2,4,5,6-trimethylbenzene crys- tallizes in the monoclinic system, space group Pbca with a = 9.842(5), b = 9.455(5), c = 22.165(12) ?, V = 2062.6(18) ?3, Dc = 1.277 g/cm3, Z = 4, C24H24N6, Mr = 396.49, μ(MoKa) = 0.079 mm-1 and F(000) = 840. The structure was refined to R = 0.0662 and wR = 0.1891 for 1163 observed reflections (I > 2σ(I)). The title molecule has trans-conformation about the central phenyl ring. The zigzag-like molecules are connected by face-to-face π…π stacking to form an infinite 2D layer.

Seismic phases from the Moho and its implication on the ultraslow spreading ridge

The Moho interface provides critical evidence for crustal thickness and the mode of oceanic crust accretion. The seismic Moho interface has not been identified yet at the magma-rich segments （46°-52°E） of the ultra- slow spreading Southwestern Indian Ridge （SWIR）. This paper firstly deduces the characteristics and do- mains of seismic phases based on a theoretical oceanic crust model. Then, topographic correction is carried out for the OBS record sections along Profile Y3Y4 using the latest OBS data acquired from the detailed 3D seismic survey at the SWIR in 2010. Seismic phases are identified and analyzed, especially for the reflected and refracted seismic phases from the Moho. A 2D crustal model is finally established using the ray tracing and travel-time simulation method. The presence of reflected seismic phases at Segment 28 shows that the crustal rocks have been separated from the mantle by cooling and the Moho interface has already formed at zero age. The 2D seismic velocity structure across the axis of Segment 28 indicates that detachment faults play a key role during the processes of asymmetric oceanic crust accretion.

Solvent Dependent Assembly,Structural Diversity and Topology Analysis in Two Novel Ni Coordination Polymers

Solvent dependent assembly obtained two novel Ni coordination polymers with H_2 tbtpa and flexible 1,2-bix ligand（H_2tbtpa = tetrabromoterephthalic acid and 1,2-bix = 1,2-bis（imidazol-1-ylmethyl）benzene）,formulated as [Ni_（0.5）（tbtpa）_（0.5）（1,2-bix）·（H_2O）]_n（1） and [Ni（tbtpa）（1,2-bix）（H_2O）_2]_n（2）.They have been structurally characterized by single-crystal and powder X-ray diffraction,elemental analysis,FT-IR spectra and TGA.Compound 1 crystalizes in triclinic,space group P1 with a = 9.0276（4）,b = 10.0012（6）,c = 11.4955（5） A,α = 69.121（5）,β = 76.398（4）,γ = 89.668（4）o,C_（36）H_（32）Br_4 Ni N_8O_6,Mr = 1051.04,V = 939.05（8） A^3,Z = 1,Dc = 1.859 g·cm^-3,μ = 6.222 mm^-1,F（000） = 520,8.502≤2θ≤134.16°,λ（Cu Kα） = 1.54184 A,T = 294（6） K,the final R = 0.0750,w R = 0.1988 and S = 1.033.Compound 2 crystalizes in triclinic,space group P1 with a = 11.1257（7）,b = 11.5062（6）,c = 12.3529（4） A,α = 88.861（3）,β = 84.572（4）,γ = 64.235（6）o,C_（22）H_（18）Br_4 Ni N_4O_6,Mr = 812.75,V = 1417.36（1） A^3,Z = 2,Dc = 1.904 g·cm^-3,μ = 7.968 mm^-1,F（000） = 788,7.2≤2θ≤134.1°,λ（Cu Kα） = 1.54184 A,T = 294（6） K,the final R = 0.0414,w R = 0.0865 and S = 1.025.1 shows a two-dimensional（4,4）-sql topology and 2 manifests a three-dimensional 6~58 Cd SO_4 topology coordination polymer network.

Chiral cation promoted interfacial charge extraction for efficient tin-based perovskite solar cells

Pb-free Sn-based perovskite solar cells(PSCs) have recently made inspiring progress, and power conversion efficiency(PCE) of 14.8% has been achieved. However, due to the energy-level mismatch and poor interfacial contact between commonly used hole transport layer(i.e., poly(3,4-ethylenedioxythio phene):poly(styrene sulfonate), PEDOT:PSS) and FASnI_(3) film, it is still challenging to effectively extract holes at the interface. Owing to the p-type nature of Sn-based perovskites, the efficient hole extraction is of particular significance to improve the PCE of their solar cells. In this work, for the first time, the role of chiral cations, a-methylbenzylamine(S-/R-/rac-MBA), in promoting hole transportation of FASnI_(3)-based PSCs is demonstrated. The introduction of MBAs is found to form 2D/3D film with lowdimensional structures locating at PEDOT:PSS/FASnI_(3) interface, which facilitates the energy level alignment and efficient charge transfer at the interface. Importantly, chiral-induced spin selectivity(CISS)effect of R-MBA_(2)SnI_(4)induced by chiral R-MBA cation is found to further assist the specific interfacial transport of accumulated holes. As a result, R-MBA-based PSCs achieve decent PCE of 10.73% with much suppressed hysteresis and enhanced device stability. This work opens up a new strategy to efficiently promote the interfacial extraction of accumulated charges in working PSCs.

A Novel Three-dimensional Mn(Ⅱ) Coordination Polymer Constructed from Biphenyl-3,3',5,5'-tetracarboxylic Acid and Water

The title Mn（Ⅱ） coordination polymer,poly{[heptaaqua-（μ4-bi-phenyl-3,3？,5,5？-tetracarboxylate）-bimanganese（Ⅱ）] pentahydrate},[Mn_2（bpta）（H_2O）_7]_n·5n H_2O（I）,is crystallized from a mixture of biphenyl-3,3？,5,5？-tetracarboxylic acid（H_4bpta） and MnCl_2·4H_2O in waterethanol under room temperature. Its asymmetric unit consists of one and two halves of crystallographically independent Mn（Ⅱ） cations,one fully deprotonated H4 bpta ligand,seven coordinated water molecules and five solvent water as guest molecules. In I,each Mn（Ⅱ） atom is octahedrally coordinated by six oxygen atoms from bpta^（4-） anions and coordinated water molecules. In the Mn（Ⅱ） cations,one half Mn（Ⅱ） ion of them located at a 2-fold axis generating a trinuclear [Mn_3（H_2O）_2（RCOO）_2] linker by μ1,1-O（water） and μ1,3-O,O？（carboxylate） bridges and another half Mn（Ⅱ） ion with an inversion is a mononuclear linker. These neighbouring trinuclear and mononuclear Mn（Ⅱ） cations are linked together by biphenyl-3,3？,5,5？-tetracarboxylates to form a three-dimensional framework with a（42.84） topology of a（4,4）-connected net,in which the positions of the trinuclear [Mn_3（H_2O）_2（R-COO）_2] linker as a 4-connector linking four bpta^（4-） ligands in I reproduce an eagle-shaped arrangement. The polymeric structure exhibits a water channel with an accessible void of 797.1 ？~3,amounting to 15.7% of the total unit-cell volume. Each of the cavities in the network is occupied by solvent water molecules.

Catalytic oxidation of benzene over nanostructured porous Co_3O_4-CeO_2 composite catalysts

Mesostructured Co3O4-CeO2 composite was found to be an effective catalytic material for the complete oxidation of benzene. The Co3O4-CeO2 catalysts with different Co/Ce ratios （mol/mol） were prepared via the nanocasting method and the mesostructure was replicated from two-dimensional （2D） hexagonal SBA-15 and three-dimensional （3D） cubic KIT-6 silicas, respectively. All the obtained Co3O4-CeO2 catalysts exhibited the similar symmetry with the parent silicas and well ordered mesostructures. The Co3O4- CeO2 catalysts with 2D mesostructure showed lower catalytic activities than the corresponding 3D materials. The Co3O4-CeO2 catalyst nanocasted from KIT-6 and with the Co/Ce ratio of 16/1 possessed the best catalytic benzene oxidation activity due to larger quantities of surface hydroxyl groups and surface oxygenated species. The mesostructured Co3O4-CeO2 material thus shows great potential as a promising eco-environmental catalyst for benzene effective elimination.

MXene coupled with molybdenum dioxide nanoparticles as 2D-0D pseudocapacitive electrode for high performance flexible asymmetric micro-supercapacitors

Recently,two-dimensional(2D)transition metal carbides and carbonitrides(MXenes),have shown great potential in micro-supercapacitors(MSCs).However,the maximum voltage output of symmetric MXene MSCs is limited to 0.6 V due to the oxidation effects at high anodic potentials.Herein,we developed asymmetric micro-supercapacitors(AMSCs)based on titanium carbide MXene(Ti_(3)C_(2)Tx)and MXene-MoO_(2) electrodes with an enlarged voltage window of 1.2 V,which is twice wider than that of symmetric MXene MSCs.The 2D-0D MXene-MoO_(2) microelectrode is fabricated by homogenous dispersing zerodimensional(0D)MoO_(2) nanoparticles into MXene layers to impede layers stacking and MoO_(2) nanoparticles aggregation.Notably,the AMSCs delivered good electrochemical performances of areal capacitance of ~19 mF cm^(-2) and volumetric capacitance of 63 F cm^(-3) at a scan rate of 2 mV s^(-1),and high energy density of 9.7 mW h cm^(-3) at a power density of 0.198 W cm^(-3).The AMSCs also presented exceptionally mechanical flexibility under different bending states and excellent cyclic stability,with 88% capacitance retention after 10000 cycles at a discharge current density of 0.5 mA cm^(-2).For practical application,the serially connected AMSCs are fully affordable to power electronics,which is beneficial for soft and wearable power devices.

Synthesis and characterization of two-dimensional lead-free(K, Na)NbO3 micro/nano piezoelectric structures

Two-dimensional(2 D)lead-free(K,Na)Nb O3(KNN)micro/nano structures with controllable K/Na ratio were successfully fabricated via a two-step molten salt synthesis(MSS).In this work,the reaction factors,including the proportion of molten salts,the types of carbonates,the sintering temperature,and the sintering time,were discussed in detail and the optimized condition was identified.The microstructure of KNN was confirmed by confocal Raman spectroscopy,while piezoresponse force microscopy(PFM)was applied to measure three-dimensional(3 D)morphology and piezoelectric properties of KNN particles.The as-synthesized KNN platelets apparently possess anisotropic morphology and uniform structure,the size of which reaches 5–20μm in length/width and 0.5–1μm in thickness.It should be noted that the K/Na ratios of the KNN crystals are basically consistent while the proportion of salts changes within a certain range.The enrichment of Na element in the products is also observed,which owes to the smaller ionic radius of Na+comparing to that of K+.This result provides a reference for the further preparation of textured ceramics and flexible piezoelectric generators.

An attempted approach to the tricyclic core of haliclonin A：Structural elucidation of the final product by 2D NMR

We describe the design and execution of a novel synthetic route to the tricyclic core of haliclonin A,a tetracyclic marine natural product.The approach features Bachi＇s thiol-medicated free radical cyclization of alkenyl isocyanide to build the bridged ring system,and ring-closing metathesis（RCM） reaction to form the macrocycle.Execution of the synthetic plan ultimately resulted in a diazatricyclic compound.By means of 2D NMR techniques,the structure of this compound was revealed to an unexpected product 8.Analysis of the synthetic pathways allowed concluding that the unexpected product is a result of an ＂unexpected＂ migration of olefinic bond during dioxolanation of the 2-cyclohexenone derivative 7.This investigation also resulted in a concise construction of the functionalized hexahydro-1H-isoindole-1,5（4H）-dione 12 and the macrocyclic tricyclic ring system 8.

MoS_(2)core-shell nanoparticles prepared through liquid-phase ablation and light exfoliation of femtosecond laser for chemical sensing

Molybdenum disulfide(MoS_(2))-based nanostructures are highly desirable for applications such as chemical and biological sensing,photo/electrochemical catalysis,and energy storage due to their unique physical and chemical properties.In this work,MoS_(2)core-shell nanoparticles were first prepared through the liquid-phase processing of bulk MoS2by a femtosecond laser.The core of prepared nanoparticles was incompletely and weakly crystalline MoS_(2);the shell of prepared nanoparticles was highly crystalline MoS_(2),which wrapped around the core layer by layer.The femtosecond laser simultaneously achieved liquid-phase ablation and light exfoliation.The formation mechanism of the core-shell nanoparticles is to prepare the nanonuclei first by laser liquid-phase ablation and then the nanosheets by light exfoliation;the nanosheets will wrap the nanonuclei layer by layer through van der Waals forces to form core-shell nanoparticles.The MoS_(2)core-shell nanoparticles,because of Mo-S bond breakage and recombination,have high chemical activity for chemical catalysis.Afterward,the nanoparticles were used as a reducing agent to directly prepare three-dimensional(3D)Au-MoS_(2)micro/nanostructures,which were applied as surface-enhanced Raman spectroscopy(SERS)substrates to explore chemical sensing activity.The ultrahigh enhancement factor(1.06×10^(11)),ultralow detection limit(10-13M),and good SERS adaptability demonstrate highly sensitive SERS activity,great ability of ultralow concentration detection,and ability to detect diverse analytes,respectively.This work reveals the tremendous potential of 3D Au-MoS_(2)composite structures as excellent SERS substrates for chemical and biological sensing.

One-step fabrication of two-dimensional hierarchical Mn_(2)O_(3)@graphene composite as high-performance anode materials for lithium ion batteries

Two-dimensional(2 D) hierarchical Mn_(2)O_(3)@graphene composite is synthesized by a one-step solid-phase reaction. The nanosheets of Mn_(2)O_(3) are vertically grown on few-layered graphene, constructing a unique2 D hierarchical structure. As an anode material for lithium-ion batteries(LIBs), this hierarchical composite displays excellent electrochemical performances, showing an extraordinary reversible discharge capacity of 2125.9 mA hg^(–1). Moreover, a record high reversible capacity of 1746.8 mA hg^(–1) is maintained after 100 cycles at a current density of 100 mA g^(–1), which retains 82.2 % of the initial capacity. Such an outstanding performance could be attributed to its novel structure and the synergistic effects between the Mn_(2)O_(3) and graphene.