Layer-by-layer evolution and a hysteretic single-crystal to single-crystal transformation cycle of a flexible pillared-layer open framework

Two hypothetical crystal-growth intermediates of a new pillared-layer framework have been isolated. The seemingly rigid pillared-layer framework also undergoes temperature-induced, time-dependent, hysteretic framework distortion.     

Al-TS-1的合成及催化氧化性能

系统研究了Al掺杂TS-1(Al-TS-1)分子筛的合成及其催化氧化性能,采用X射线衍射、紫外-可见光谱、电感耦合等离子体发射光谱、扫描电镜、²⁷Al和²⁹Si固体核磁共振等手段对Al-TS-1样品进行了表征.结果表明,在合成过程中,Al的引入会影响TS-1中骨架Ti的形成,但当Al含量低于一定值(Al/Si≤0.005)时,其影响很小.Al-TS-1中骨架Al和骨架Ti均不对其相应的酸催化和催化氧化作用产生影响.骨架Al抑制了Al-TS-1在碱性应用体系中的与Ti相邻Si的溶脱,从而保护了骨架Ti活性中心.     

Chemical applications of topology and group theory 13. Chirality and framework groups [1]

Pople has recently introduced the concept of a framework group to specify the full symmetry properties of a molecular structure. Furthermore, Pople has developed powerful algorithms for the use of framework groups to generate all distinguishable skeletons with a given number of sites. This paper studies the systematics of chirality arising from different framework groups. In this connection framework groups can be classified into four different types: linear, planar, achiral, and chiral. Chiral framework groups lead to chiral systems for any ligand partition including that with all ligands equivalent. Linear framework groups are never chiral even for the ligand partition with all ligands different. Planar framework groups are also never chiral since all sites are in the same plane, which therefore remains a symmetry plane for any ligand partition. However, the mirror symmetry of the molecular plane of a planar framework group can be destroyed by a process called polarization; this process can be viewed as the mathematical analogue of complexing a planar aromatic hydrocarbon to a transition metal. The chirality of four-, five-, and six-site framework groups is discussed in terms of the maximum symmetry ligand partitions resulting in removal of all of the symmetry elements corresponding to improper rotations S _n (including reflections S ₁ and inversions S ₂) from achiral and polarized planar framework groups. The Ruch-Schönhofer group theoretical algorithms for the calculation of chiral ligand partitions and pseudoscalar polynomials of lowest degree (“chirality functions”) are adapted for use with these framework groups. Other properties of framework groups relevant to a study of their chirality are also discussed: these include their transitivity (i.e. whether all sites are equivalent or not), their normality (i.e. whether proper rotations correspond to even permutations and improper rotations correspond to odd permutations), and the number of sites in their symmetry planes.     

中学生“原子结构”相异构想的认知成因分析及转变策略

物质结构内容的抽象性导致学生产生大量的相异构想,影响着学生对化学概念的学习和深刻理解。通过整合国内外相关研究结果,从思维的视角分析了中学生“原子结构”相异构想产生的原因,并提出转变学生相异构想、促进概念理解的教学策略。     

水溶性三维有序超分子和共价有机聚合物

总结了近年来在水溶性三维超分子聚合物、 超分子有机框架、 超分子-金属有机框架杂化结构、 超分子-共价-金属有机框架杂化结构及共价有机框架合成、 催化和输送功能方面的研究进展, 指出了有序三维聚合物未来研究面临的挑战并展望今后的发展方向.     

Tetrahedral framework nucleic acids promote cognitive impairment recovery post traumatic brain injury

Cognitive impairment often occurs after post traumatic brain injury. In addition, recovery of cognitive impairment is largely dependent on spontaneous repair and the severity of secondary insult. The tetrahedral framework nucleic acid is a novel nanostructure has been shown to have a positive biological effect in promoting regeneration and anti-inflammation. To explore the treatment effect of tetrahedral framework nucleic acids for cognitive impairment recovery post traumatic brain injury, we established a mouse model of traumatic brain injury and verified the efficacy of tetrahedral framework nucleic acids in promoting cognitive impairment recovery post traumatic brain injury. The results show that the tetrahedral framework nucleic acids promoted the recovery of post-traumatic cognitive function by enhancing the proliferation of endogenous neural stem cells. Besides, tetrahedral framework nucleic acids modulated the neuroinflammatory response in the acute phase by inhibiting excessive astrocyte and microglial activation. Taken together, the results of the study indicate tetrahedral framework nucleic acids for treatment of cognitive impairment post traumatic brain injury.     

Surfactant-assisted fabrication of graphene frameworks endowing epoxy composites with superior thermal conductivity

With the rapid growth in electronic device performance,there has been an increasing demand for thermally conductive polymer composites to handle the thermal management issue,thus contributing to the great importance to develop the graphene framework,which is evaluated as the most promising reinforcements for enhancing the thermal conductivity of polymer.Vacuum filtration is a common method to fabricate graphene framework,whereas,it is available to prepare a framework with centimeter-scale thickness by filtrating the graphene-water dispersion,due to the fact of sample cracking caused by the mismatch of surface tension between graphene and water.In this work,a surfactantassisted strategy was proposed by adjusting the surface tension of the water close to that of graphene first,then performing a conventional filtration process,to fabricate graphene framework.As a result,a thick graphene framework(thickness:3 cm)was successfully prepared,and after embedding into epoxy,the framework endows the composite(13.6 wt%)with a high in-plane thermal conductivities of12.4 W/mK,which is equivalent to≈64 times higher than that of neat epoxy.Our method is simple and compatible with the conventional filtration process,suggesting great potential for the mass-production of graphene framework to meet the practical application requirements.     

Phase Transformations in Alkaline and Acid Leached Y Zeolites Dealuminated by Steaming

The steaming of zeolite Y (here at 873 K for 7 hours) leads to the formation of an amorphous aluminium aluminosilicate in addition to the dealuminated zeolite (DAY). An alkaline treatment of DAY causes the transformation of the non‐framework phase into an alkali aluminosilicate and the partial desilication of the DAY framework. The alkali aluminosilicate is decomposed by a moderate acid leaching under the formation of silica gel. The ²⁹Si MAS NMR and IR spectra of DAY and its chemically treated modifications are superimposed by the signals of the crystalline zeolite framework and the amorphous non‐framework materials whereas XRD measurements only characterize the current state of the framework.     

ZSM-5沸石骨架铝迁移规律的研究 Ⅲ.ZSM-5沸石骨架铝迁移的可逆性

考察了水热条件下HZSM-5沸石骨架铝的迁出,气-固或液-固反应条件下外界铝进入骨架的影响因素及表面性质的变化。发现在相同的条件下,随ZSM-5沸石硅铝比的增加,铝迁入骨架的比率增大;经水热处理后较相同数量级硅铝比的未经处理的沸石的铝迁入骨架速率快,结合骨架铝迁移的机理对此现象进行了讨论。在400℃气-固反应时,进入沸石骨架的铝量达400—600℃总量的75—80％,和在400℃水热处理时骨架铝的迁脱量相当(80％),这部分铝主要对应于强酸中心位,说明沸石骨架中对应于酸中心较强而稳定性较弱的铝易迁出也易迁入,表明酸性中心是可逆的。     

Selective Dealumination of ZSM-5 by Hydrothermal Treatment

ThealundniumdistributionoverZSM-5crystalshasl0ngbeenofinterest.Thecatalyticbehaviorandphysicalpr0pertiesofzeoliteZSM-5arecloselyrelatedt0thealuminiumlcontentanddistributi0nintheframework.ThemolecularshaPeselectivecatalysisarisesfromthepresence0factivesiteswithintheintracrystallinefreevolumeof...lit.,',whicharerelatedt0theframew0rkalUminium.Inordert0changethealuInininmdistributionintheZSM-5strUctUreandmeettheneedsofvariousrequirements,aseriesofmethodshasbeendeveloPed,includingtreatmentwit…     

Evolution of an Adenine–Copper Cluster to a Highly Porous Cuboidal Framework: Solution‐Phase Ripening and Gas‐Adsorption Properties

The synthesis and directed evolution of a tetranuclear copper cluster, supported by 8‐mercapto‐N9‐propyladenine ligand, to a highly porous three‐dimensional cubic framework in the solid state is reported. The structure of this porous framework was unambiguously characterized by X‐ray crystallography. The framework contains about 62 % solvent‐accessible void; the presence of a free exocyclic amino group in the porous framework facilitates reversible adsorption of gas and solvent molecules. Oriented growth of framework in solution was also tracked by force and scanning electron microscopy studies, leading to identification of an intriguing ripening process, over a period of 30 days, which also revealed formation of cuboidal aggregates in solution. The elemental composition of these cuboidal aggregates was ascertained by EDAX analysis.     

Design of molecularly ordered framework of mesoporous silica with squared one-dimensional channels

Mesoporous silica with squared one-dimensional channels (KSW-2-type mesoporous silica), possessing a molecularly ordered framework arising from a starting layered polysilicate kanemite, was obtained through silylation of a surfactant (hexadecyltrimethylammonium, C16TMA)-containing mesostructured precursor with octoxytrichlorosilane (C8H17OSiCl3) and octylmethyldichlorosilane (C8H17(CH3)SiCl2). The presence of the molecular ordering in the silicate framework was confirmed by XRD and TEM. Octoxy groups grafted on KSW-2 can be eliminated by subsequent hydrolysis under very mild condition, and pure mesoporous silica was obtained with the retention of the kanemite-based framework. The framework is structurally stabilized by the attachment of additional SiO4 units to the framework, and the mesostructural ordering hardly changed under the presence of water vapor. A large number of silanol groups remained at the mesopore surfaces because C16TMA ions and octoxy groups can be removed without calcination. Octylmethylsilyl groups are regularly arranged at the mesopore surface due to the molecular ordering in the silicate framework. The molecularly ordered structural periodicity originating from kanemite is retained even after calcination at 550 degrees C, while that in the precursor without silylation disappeared. The synthetic strategy is quite useful for the design of the silicate framework of mesostructured and mesoporous materials with and without surface functional organic groups.     

杂原子(B、Ti、Fe)进入Y型分子筛骨架的表征

应用X射线粉末衍射(XRD)、傅立叶变换红外光谱(FT-IR)、固体核磁共振(NMR)、紫外可见漫反射(UV-Vis-DRS)和热重(TG)等多种表征方法对合成的杂原子Y分子筛(BY、TiY、FeY)的结构进行了表征. 根据引入杂原子后分子筛的晶胞常数、骨架伸缩振动吸收峰、杂原子的特征电子跃迁峰、还原的热重曲线以及杂原子所处的微观配位环境等多种性质的变化, 得出结论：杂原子B、Ti、Fe均已进入Y分子筛骨架.     

The McMillan–Mayer framework and the theory of electrolyte solutions

In electrolyte thermodynamics one often speaks of two thermodynamic frameworks; the Lewis–Randall framework (characterised by temperature, pressure, and mole numbers) and the McMillan–Mayer framework (characterised by temperature, total volume, solute mole numbers, and solvent chemical potential). However, there is only one framework in thermodynamics; the apparent difference between the two ‘frameworks’ is, in electrolyte thermodynamics, due to the change in the pressure caused by the charging process at constant volume and solvent chemical potential.The so-called McMillan–Mayer framework is set in the context of the classical thermodynamics and the use of it is examplified by the Debye–Hckel theory. The so-called McMillan–Mayer framework is superfluous when the thermodynamics of the electrolyte solutions is described by the Helmholtz energy functions.     

JACOB: An enterprise framework for computational chemistry

Here, we present just a collection of beans (JACOB): an integrated batch‐based framework designed for the rapid development of computational chemistry applications. The framework expedites developer productivity by handling the generic infrastructure tier, and can be easily extended by user‐specific scientific code. Paradigms from enterprise software engineering were rigorously applied to create a scalable, testable, secure, and robust framework. A centralized web application is used to configure and control the operation of the framework. The application‐programming interface provides a set of generic tools for processing large‐scale noninteractive jobs (e.g., systematic studies), or for coordinating systems integration (e.g., complex workflows). The code for the JACOB framework is open sourced and is available at: www.wallerlab.org/jacob . © 2013 Wiley Periodicals, Inc.     

Trapping guests within a nanoporous metal-organic framework through pressure-induced amorphization

The release of guest species from within a nanoporous metal-organic framework (MOF) has been inhibited by amorphization of the guest-loaded framework structure under applied pressure. Thermogravimetric analyses have shown that by amorphizing ZIF-8 following sorption of molecular I(2), a hazardous radiological byproduct of nuclear energy production, the pore apertures in the framework are sufficiently distorted to kinetically trap I(2) and improve I(2) retention. Pair distribution function (PDF) analysis indicates that the local structure of the captive I(2) remains essentially unchanged upon amorphization of the framework, with the amorphization occurring under the same conditions for the vacant and guest-loaded framework. The low, accessible pressure range needed to effect this change in desorption is much lower than in tradition sorbents such as zeolites, opening the possibility for new molecular capture, interim storage, or controlled release applications.     

High-rate charge-carrier transport in porphyrin covalent organic frameworks: switching from hole to electron to ambipolar conduction

Well conducted: a two-dimensional porphyrin covalent organic framework is described. Owing to the eclipsed stacking alignment, the framework is conductive and allows high-rate carrier transport through the porphyrin columns. The central metal in the porphyrin rings changes the conducting nature of the material from hole to electron, and to ambipolar conduction. It also drives the high on-off ratio photoconductivity of the framework.     

Synthesis of Chiral MOF-74 Frameworks by Post-Synthetic Modification by Using an Amino Acid

The synthesis of chiral metal–organic frameworks (MOFs) is highly relevant for asymmetric heterogenous catalysis, yet very challenging. Chiral MOFs with MOF-74 topology were synthesised by using post-synthetic modification with proline. Vibrational circular dichroism studies demonstrate that proline is the source of chirality. The solvents used in the synthesis play a key role in tuning the loading of proline and its interaction with the MOF-74 framework. In N,N′-dimethylformamide, proline coordinates monodentate to the Zn²⁺ ions within the MOF-74 framework, whereas it is only weakly bound to the framework when using methanol as solvent. Introducing chirality within the MOF-74 framework also leads to the formation of defects, with both the organic linker and metal ions missing from the framework. The formation of defects combined with the coordination of DMF and proline within the framework leads to a pore blocking effect. This is confirmed by adsorption studies and testing of the chiral MOFs in the asymmetric aldol reaction between acetone and para-nitrobenzaldehyde.     

脱铝Y型沸石铝化的研究

以不同浓度的KOH溶液分别处理SDY和EDY制备了ASDY和AEDY系列样品。然后采用XRD, FTIR, NH3TPD, 低温N2吸附及正庚烷裂解反应来表征ASDY和AEDY样品的孔结构, 酸性及催化性能的变化。证实了KOH溶液溶解非骨架铝后, 铝原子重新进入SDY的骨架, 导致Si/Al比降低。而且还发现在一定浓度的KOH溶液处理SDY时, 有部分骨架Si被脱出。在没有外加铝源的情况下, KOH溶液也可以铝化EDY样品, KOH溶液首先溶解EDY表面相及二次孔周围的沸石骨架, 然后这些溶解下来的铝碎片再填充到EDY的骨架空位中去, 致使其Si/Al比降低。