Zeolite nanocrystals inside mesoporous TUD-1: a high-performance catalytic composite

A hierarchically structured composite material with interconnecting meso- and micropores has been developed with the aim to optimize zeolite performance. A general synthetic method has been developed that, in a controlled manner, allows for various types of nanosized zeolite to be incorporated into a three-dimensional mesoporous matrix. Nanosized zeolite Beta was used to exemplify this new approach, resulting in a system in which zeolite Beta shows a higher cracking activity per gram of zeolite than pure nanosized zeolite Beta for the model feed n-hexane. Additionally, FTIR studies of CO and NH3 adsorption revealed that the nature of the acid sites in the nanozeolite has been partially modified due to the interactions with the mesoporous matrix, TUD-1.     

Modulating Hierarchical Micro/Mesoporosity by a Mixed Solvent Approach in Al-MOF: Stabilization of MAPbBr3 Quantum Dots

Various hierarchical micro/mesoporous MOFs based on {[Al(μ-OH)(1,4-NDC)]⋅H₂O} ( MOF1 ) with tunable porosities (pore volume and surface area) have been synthesized by assembling Al^III and 1,4-NDC (1,4-naphthalenedicarboxylate) under microwave irradiation by varying water/ethanol solvent ratio. Water/ethanol mixture has played a crucial role in the mesopore generation in MOF1M₂₅ , MOF1M₅₀ , and MOF1M₇₅ , which is achieved by in situ formation of water/ethanol clusters. By adjusting the ratio of water/ethanol, the particle size, surface area and micro/mesopore volume fraction of the MOFs are controlled. Furthermore, reaction time plays a critical role in mesopore formation as realized by varying reaction time for the MOF with 50 % ethanol ( MOF1M₅₀ ). Additionally, hierarchical MOF ( MOF1M₅₀ ) has been used as a template for the stabilization of MAPbBr₃ (MA=methylammonium) perovskite quantum dots (PQDs). MAPbBr₃ PQDs are grown inside MOF1M₅₀ , where mesopores control the size of PQDs which leads to quantum confinement.     

Thermoelectricity Generation and Electron–Magnon Scattering in a Natural Chalcopyrite Mineral from a Deep‐Sea Hydrothermal Vent

Current high‐performance thermoelectric materials require elaborate doping and synthesis procedures, particularly in regard to the artificial structure, and the underlying thermoelectric mechanisms are still poorly understood. Here, we report that a natural chalcopyrite mineral, Cu_1+xFe_1?xS₂, obtained from a deep‐sea hydrothermal vent can directly generate thermoelectricity. The resistivity displayed an excellent semiconducting character, and a large thermoelectric power and high power factor were found in the low x region. Notably, electron–magnon scattering and a large effective mass was detected in this region, thus suggesting that the strong coupling of doped carriers and antiferromagnetic spins resulted in the natural enhancement of thermoelectric properties during mineralization reactions. The present findings demonstrate the feasibility of thermoelectric energy generation and electron/hole carrier modulation with natural materials that are abundant in the Earth’s crust.     

The First Conducting Spin-Crossover Compound Combining a MnIII Cation Complex with Electroactive TCNQ Demonstrating an Abrupt Spin Transition with a Hysteresis of 50 K

We present herein the synthesis, crystal structure, and electric and magnetic properties of the spin-crossover salt [Mn(5-Cl-sal-N-1,5,8,12)]TCNQ_1.5 ⋅ 2 CH₃CN ( I ), where 5-Cl-sal-N-1,5,8,12=N,N′-bis(3-(2-oxy-5-chlorobenzylideneamino)propyl)-ethylenediamine, containing distinct conductive and magnetic blocks along with acetonitrile solvent molecules. The Mn^III complex with a Schiff-base ligand, [Mn(5-Cl-sal-N-1,5,8,12)]⁺, acts as the magnetic unit, and the π-electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ⁻) is the conducting unit. The title compound ( I ) exhibits semiconducting behavior with room temperature conductivity σ_RT≈1×10⁻⁴ ohm⁻¹ cm⁻¹ and activation energy Δ ≈0.20 eV. In the temperature range 73–123 K, it experiences a hysteretic phase transition accompanied by a crossover between the low-spin S=1 and high-spin S=2 states of Mn^III and changes in bond lengths within the MnN₄O₂ octahedra. The pronounced shrinkage of the basal Mn−N bonds in I at the spin crossover suggests that the d orbital is occupied/deoccupied in this transition. Interestingly, the bromo isomorphic counterpart [Mn(5-Br-sal-N-1,5,8,12)]TCNQ_1.5 ⋅ 2 CH₃CN ( II ) of the title compound evidences no spin-crossover phenomena and remains in the high-spin state in the temperature range 2–300 K. Comparison of the chloro and bromo compounds allows the thermal and spin-crossover contributions to the overall variation in bond lengths to be distinguished. The difference in magnetic behavior of these two salts has been ascribed to intermolecular supramolecular effects on the spin transition. Discrete hydrogen bonding exists between cations and cations and anions in both compounds. However, the hydrogen bonding in the crystals of II is much stronger than in I . The relatively close packing arrangement of the [Mn(5-Br-sal-N-1,5,8,12)]⁺ cations probably precludes their spin transformation.     

DSC Investigations on a Commercial Photocuring Sheet Material

The photopolymerization of a commercial sheet material as used in the dental laboratory was investigated by using the photocalorimeter DSC7/DPA7 (Perkin-Elmer). Using normal reaction conditions (light wavelength 400 nm, light intensity 1 mW cm^–2 and sample thickness 2.5 mm), the curing was completed within few min. The reaction rate was nearly independent on the light wavelength in the range between =300 and 380 nm, but decreased distinctively at longer wavelengths. After desmearing the DSC curves, the dependence of the reaction rate on light intensity and sample thickness could be described in very good approximation by an equation derived by Tryson [1]. Comparable with pure acrylates or methacrylates, a pronounced dark reaction was found after interruption of the illumination.This revised version was published online in November 2005 with corrections to the Cover Date.     

Microemulsion‐Assisted Preparation of a Mesoporous Ferrihydrite/SiO2 Composite for the Efficient Removal of Formaldehyde from Air

Mesoporous ferrihydrite/SiO₂ composites were synthesized according to a water‐in‐oil microemulsion method and characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetry, nitrogen‐adsorption/desorption, and by X‐ray photoelectron spectroscopy. The as‐prepared porous ferrihydrite/SiO₂ composites showed an excellent adsorption performance for formaldehyde (HCHO) removal from indoor air at ambient temperature. It was found that the aging time during the synthesis had a significant impact on the pore structure, surface area, and HCHO adsorption of these materials. The ferrihydrite/SiO₂ composite that was aged for 3 h in the presence of tetraethyl orthosilicate (TEOS) exhibited a relatively high HCHO adsorption capacity, as well as good recyclability, which was attributed to a relatively large BET surface area, optimal pore size, a suitable Si/Fe atomic ratio, and a synergistic effect between ferrihydrite and SiO₂. This work not only demonstrates that porous ferrihydrite/SiO₂ composites can act as an efficient adsorbent toward HCHO, but suggests a new route for the rational design of cost‐effective and environmentally benign adsorbents with high performance for indoor air purification.     

Reversibly switching the function of a surface between attacking and defending against bacteria

Attack or defend! A smart polymer surface has two reversibly switchable equilibrium states, a cationic N,N-dimethyl-2-morpholinone (CB-Ring) and a zwitterionic carboxy betaine (CB-OH). CB-Ring will kill bacteria upon contact under dry conditions, whereas CB-OH will release the previously attached and dead bacteria and further resist adhesion of bacteria under wet conditions.     

Decametallic CoII‐Cluster‐Based Microporous Magnetic Framework with a Semirigid Multicoordinating Ligand

We have synthesized a microporous magnetic framework that contained supertetrahedral decametallic cobalt clusters as nodes and 4‐(tris(hydroxymethyl)methyl)pyridine ligands as linkers in a NaCl‐like network. This complex shows canted antiferromagnetism with spin‐glass behavior. After the removal of the guest molecules, the spin‐canting and spin‐glass behaviors are maintained. The permanent porosity was evaluated by N₂‐adsorption measurements. This complex mainly shows a hydrophobic nature, as validated by MeOH‐ and water‐adsorption measurements, which is consistent with the grand canonical Monte Carlo (GCMC) theoretical simulation.     

基于三苯胺和芴的D—A型高分子信息存储材料的合成及性能

设计和合成了一种高度可溶的基于三苯胺和芴的D—A型高分子信息存储材料PFTD（Poly{[4，4L（4．4’-（9H—fluorene一9，9-diyl）bis（4，1-phenylene））bis（oxy）diphthalonitrile][triphe—nylamine]E9，9-dioctyl-9H—fluorene]}）。随着溶剂极性的增加，荧光强度逐渐减弱，荧光发射谱带变宽且发生红移，最大发射峰分别位于426nm（甲苯），432nm（四氢呋喃），r142nm（苯腈），445nm（N，N-二甲基甲酰胺）。PFTD在THF稀溶液中的绝对荧光量子效率为47．8％，由于固体时强的荧光淬灭效应，旋涂在石英玻璃片上的薄膜绝对荧光量子效率仅为5．5％。通过电化学实验估算得到的HOMO、LUMO、能隙、离子化势和电子亲和势分别为-5．43、-2．62、2．81、5．69、2．88eV。由该聚合物制备的薄膜器件（器件结构：ITO／PFTD／A1）表现出典型的一次写入、多次读出（WORM）型记忆特性，电流开关比大于10^4，开启电压为-1．5V。     

Extra‐Large Mechanical Anisotropy of a Hydrogel with Maximized Electrostatic Repulsion between Cofacially Aligned 2D Electrolytes

In our previous work, we have shown that “electrostatic forces”, when generated anisotropically in aqueous media by 2D electrolytes upon cofacial orientation, enable the formation of a hydrogel with an anisotropic parameter, as defined by the ratio of elastic moduli E_⊥/E_∥, of 3.0. Herein, we successfully developed the design strategy for a hydrogel with an anisotropic parameter of no less than 85. This value is not only 28 times greater than that of our previous anisotropic hydrogel but also 6 times larger than the current champion record in synthetic hydrogels (E_⊥/E_∥～15). Firstly, we simply lowered ionic contaminants in the hydrogel and were able to enhance the anisotropic parameter from 3.0 to 18. Then, we chose a supporting polymer network allowing the hydrogel to carry a higher interior permittivity. Consequently, the anisotropic parameter was further enhanced from 18 to 85. Owing to the enhanced mechanical anisotropy, our new hydrogel displayed a superb ability of seismic isolation.     

Use of a Profluorophore for Visualization of the Rupture of Capsules in Self‐Healing Coatings

An important category of self‐healing materials relies on the release of a healing agent from a capsule upon the occurrence of damage to the material. Visualization of the release of the healing agent is difficult to accomplish. Here we show that a profluorophore can successfully be used to visualize the local release of a healing agent in a self‐healing coating. A tetra‐functional thiol compound encapsulated in nanocapsules or microcapsules is dispersed in a poly(methyl acrylate) film, in which the profluorophore is molecularly dispersed. A strong fluorescence signal is observed when a cut is introduced in the film. This fluorescence provides clear evidence that the capsules rupture locally during the introduction of a cut. In a more general sense, it proves that profluorophores can be very useful in materials science.

     

The quest for a bidirectional auxetic,elastic, and enhanced fracture toughness material: Revisiting the mechanical properties of the BeH2 monolayers

Herein we show a density functional theory-based study performed on two recently predicted polymorphs of the BeH₂ monolayer, α-BeH₂ and β-BeH₂. The α-BeH₂ phase possesses an in-plane negative Poisson's ratio (NPR), introducing it into the unique group of auxetic materials. Our assessment delves into the linear-elastic and finite-strain regimes to understand both polymorphs' structural and mechanical responses to deformation. We find that the in-plane NPR is shown to be only parallel to the bonds in α-BeH₂ and remains along the uniaxial tensile path. Concomitantly, an out-of-plane transition toward auxetic is also revealed in regions exhibiting conventional Poisson's ratios, making α-BeH₂ a bidirectionally auxetic material. While phase transitions in β-BeH₂ are triggered at very short strains, α-BeH₂ displays excellent elasticity against tension, superior to that of most currently known 2D materials.     

Fabrication of hollow silica microspheres utilizing a hydrothermal approach

Hollow silica microspheres(HSMSs) have been successfully fabricated via a facile hydrothermal route using D-glucose as the sacrificial template and sodium silicate powder as the silica precursor.The resulting silica hollow particles were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and infrared spectroscopy(IR).The surface area was determined using the BET method.SEM and TEM images exhibited micro-sized silica hollow particles with a size of ~1.5μm.