An Extra-Large-Pore Pure Silica Zeolite with 16×8×8-Membered Ring Pore Channels Synthesized using an Aromatic Organic Directing Agent

Extra-large-pore zeolites for processing large molecules have long been sought after by both the academia and industry. However, the synthesis of these materials, particularly extra-large-pore pure silica zeolites, remains a big challenge. Herein we report the synthesis of a new extra-large-pore silica zeolite, designated NUD-6, by using an easily synthesized aromatic organic cation as structure-directing agent. NUD-6 possesses an intersecting 16×8×8-membered ring pore channel system constructed by four-connected (Q⁴) and unusual three-connected (Q³) silicon species. The organic cations in NUD-6 can be removed in nitric acid to yield a porous material with high surface area and pore volume. The synthesis of NUD-6 presents a feasible means to prepare extra-large pore silica zeolites by using assembled aromatic organic cations as structure-directing agents.     

Rhombicuboctahedral Ag100: Four-Layered Octahedral Silver Nanocluster Adopting the Russian Nesting Doll Model

Precise atomic structure of metal nanoclusters (NCs) is fundamental for elucidating the structure–property relationships and the inherent size-evolution principles. Reported here is the largest known FCC-based (FCC=face centered cubic) silver nanocluster, [Ag₁₀₀(SC₆H₃^3,4F₂)₄₈(PPh₃)₈]⁻: the first all-octahedral symmetric nesting Ag nanocluster with a four-layered Ag₆@Ag₃₈@Ag₄₈S₂₄@Ag₈S₂₄P₈ structure, consistent symmetry elements, and a unique rhombicuboctahedral morphology distinct from theoretical predictions and previously reported FCC-based Ag clusters. DFT studies revealed extensive interlayer interactions and degenerate frontier orbitals. The FCC-based Russian nesting doll model constitutes a new platform for the study of the size-evolution principles of Ag NCs.     

介孔SBA-15棒负载的Pd3Cl催化剂催化Sonogashira偶联反应（英文）

通过静电吸引策略将具有高度分散性的原子精确纳米团簇[Pd3Cl(PPh2)2(PPh3)3]+(Pd3Cl)负载在介孔SBA-15棒上。结构明确的Pd3Cl/SBA-15催化剂在以水作为溶剂以及温和的反应条件下对催化Sonogashira碳-碳偶联反应展现了较好的催化性能以及循环性。在此基础上,我们研究了Pd3Cl团簇结构与性能之间的关系,并证实内核的Pdδ+(0<δ<2)与配体之间的协同效应是催化反应的关键。     

On a new FeOF polymorph: Synthesis and stability

A new polymorph of FeOF (up to now only known in its rutile type structure) was prepared by using a new synthesis approach formally based on anionic exchange using the well-known layered FeOCl as precursor. The synthesis was achieved using [CH₃C(CH₂O–)₂(COO–)B] to vehicle fluorine through the formation of soluble (CH₃)₄N⁺ [CH₃C(CH₂O–)₂(COO–)BF]⁻ and using N,N-dimethylformamide (DMF) as the reacting medium. The XRD pattern of layered FeOF can be indexed with an orthorhombic cell which doubles along the b axis (which is the direction perpendicular to the layers) with respect to that of pristine FeOCl (a = 3.792(1) Å, b = 12.699(1) Å, c = 3.321(1) Å). Both thermal analysis and diffraction indicate similar stability for the layered and rutile polymorphs. Such findings are rationalized through Density Functional Theory calculations. It is found that the energy difference between the more stable rutile and layered polymorphs is practically nul. The origin of the similar stability lies in the fact that although the number of Fe–F and Fe–O bonds is different in the two structures, the strength of both the total number of Fe–O as well as Fe–F bonds are found to be almost identical. Even if the crystal and electronic structures are considerably different, the total bonding and thus, the stability of the two polymorphs, is comparable. The stability of different FeOF rutile type structures is also analyzed.     

Synthesis,Crystal Structure,and Photoluminescence Properties of One Novel D-π-D Type a-Cyanostilbene Derivative

Researches on a-cyanostilbene derivatives demonstrated them to be promising AIE or AIEE structural molecules and potential photoelectric materials. One novel a-cyanostilbene derivative, namely （E）-2-（4-butoxyphenyl）-3-（4-（diethylamino）phenyl）acrylonitrile （BPDPA）, has been designed, synthesized and characterized. The crystalline structure of BPDPA has been studied in detail. The single-crystal X-ray diffraction revealed BPDPA crystallizes in triclinic space group Pi, with a = 12.860（5）, b = 13.327（5）, c = 15.016（5）А, a = 72.650（5）, β = 66.969（5）, Y = 62.897（5）°, Mr = 696.95, V= 2085.6（13） A3, Z = 2, Dc = 1.110 g/cm-3, p = 0.068 mm1, F（000） = 752, Rint = 0.0264, R（I〉 2σ（/）） = 0.0649, wR（l〉 2σ（/） = 0.1724, R（all data） = 0.1321, wR （all data） = 0.2158, completeness to theta = 25.00 is 99.4% and GOF = 1.067. Like most reported a-cyanostilbene derivatives, BPDPA possesses a somewhat twisted molecular structure. UV-Vis and FL measurements showed an obviously bathochromic effect of BPDPA with increasing the polarity of the solvents.     

Weak acid–base interaction induced assembly for the formation of rambutan-like poly(styrene-alt-maleic anhydride)/silica composite microspheres

To investigate the effect of surface functionality on the morphology of polymer/silica composite, poly(styrene-alt-maleic anhydride) (SMA) spheres prepared via precipitation polymerization method was employed. In water/ethanol solution, diethanolamine (DEA) was used to catalyze the hydrolysis reaction of tetraethoxysilane (TEOS), and rambutan-like poly(styrene-alt-maleic anhydride)/silica (SMA/SiO₂) microspheres were synthesized through in situ sol–gel process. The obtained structure and morphology were characterized by FTIR, NMR, TEM, SEM, and TGA. The results showed that the hydrolyzed SMA chains on the surface was crucial to the nucleation and growth of silica, and the morphologies of SMA/SiO₂ composite microspheres can be controlled by the amount of DEA and the ratio of SMA/TEOS. In addition, the SMA/SiO₂ microspheres were used to prepare hierarchical structure of SMA/SiO₂/Ag particles, which were utilized for the construction of surface-enhanced Raman scattering substrate (SERS).     

Finite-time stability of Hadamard fractional differential equations in weighted Banach spaces

Nonlinear Dynamics - The main purpose of this paper is to investigate the finite-time stability of Hadamard fractional differential equations (HFDEs). Firstly, the standard definitions of...     

奇完全数的几个命题

本文证明形如3m-1的正整数不是完全数,由此推出当所有的qi≡-1(mod 3)时,奇数n=p~αП_(i=1)~sq_i~(2β_i)若是完全数,那么1/2σ(p~α)必是合数.指出k倍完全数的素因子必须满足一个不等式.运用此不等式证明当a≥n-2时形如a~(2~n)+b~(2~n)(a>b>0,a,b,n∈N~+)的奇数不是完全数.还指出当a与b都与3互素时,对于任意的正整数m,n,奇数a~(2~n)+b~(2~m)不是完全数.     

Positive solutions of the system for nth-order singular nonlocal boundary value problems

The paper deals with the existence and multiplicity of positive solutions to systems of nth-order singular nonlocal boundary value problems. The main tool used in the proof is fixed point index theory in cone. Some limit type conditions for ensuring the existence of positive solutions are given.     

Semidiscrete central-upwind scheme for conservation laws with a discontinuous flux function in space

In this paper, a modified semidiscrete central-upwind scheme is derived for the scalar conservation laws with a discontinuous flux function in space. The new scheme is based on dealing with the phase transition at the stationary discontinuity, where the unknown variable function is not continuous, but the flux function is continuous. The main advantages of the new scheme are the same as them of the original semidiscrete central-upwind scheme. Numerical results are displayed to illustrate the efficiency of the methods.