[Fe3(HCOO)6]: A Permanent Porous Diamond Framework Displaying H2/N2 Adsorption,Guest Inclusion,and Guest‐Dependent Magnetism

The porous magnet [Fe₃(HCOO)₆], the iron member of the [M₃(HCOO)₆] family (where M = Mn, Fe, Co, Ni, etc.), based on a diamond framework consisting of Fe‐centered FeFe₄ tetrahedral nodes, is prepared successfully by using a solution‐chemistry method. The as‐prepared compound, [Fe₃(HCOO)₆](CH₃OH)_1.5(H₂O)_0.5 ( 1 ‐ parent ), exhibits facile removal of its guests, methanol, and water, to give the desolvated framework [Fe₃(HCOO)₆] ( 2 ‐ empty ) that displays permanent porosity and thermal stability up to 270 °C. The flexibility of the framework and the amphiphilic nature of the surface of the pores consisting of both C–H and O arrays allows 2 ‐ empty to take up significant H₂ and N₂ at liquid‐nitrogen temperatures and a wide spectrum of both polar and nonpolar guests of different sizes. A series of guest‐inclusion compounds, [Fe₃(HCOO)₆](I₂)_0.84 ( 3 ‐ iodine ), [Fe₃(HCOO)₆](C₄H₈O) ( 4 ‐ THF ), [Fe₃(HCOO)₆](C₄H₄O) ( 5 ‐ furan ), [Fe₃(HCOO)₆](C₆H₆) ( 6 ‐ benzene ), [Fe₃(HCOO)₆](CH₃CN) ( 7 ‐ acetonitrile ), and [Fe₃(HCOO)₆]((CH₃)₂CO) ( 8 ‐ acetone ) are successfully prepared by vapor diffusion of the guest into the pores of 2 ‐ empty and their structures are characterized by using single‐crystal X‐ray crystallography. Zigzag molecular arrays of the guest are formed in the confined channels of the host framework, and the weak hydrogen‐bonding provides the main host–guest interaction. All the compounds show 3D long‐range magnetic ordering and guest‐modulated Curie temperatures, coercive fields, and remnant magnetization as a consequence of the subtle rearrangement of the magnetic framework that conforms to the size of the guests and the difference in host–guest interactions. A possible magnetic structure of the framework is proposed to account for magnetic competition and geometrical frustration. The thermal and spectroscopic properties of the compounds are also reported.     

A High‐Performance Binary Ni–Co Hydroxide‐based Water Oxidation Electrode with Three‐Dimensional Coaxial Nanotube Array Structure

Developing nanostructured Ni and Co oxides with a small overpotential and fast kinetics of the oxygen evolution reaction (OER) have drawn considerable attention recently because their theoretically high efficiency, high abundance, low cost, and environmental benignity in comparison with precious metal oxides, such as RuO₂ and IrO₂. However, how to increase the specific activity area and improve their poor intrinsic conductivity is still challenging, which significantly limits the overall OER rate and largely prevent their utilization. Thus, developing effective OER electrocatalysts with abundant active sites and high electrical conductivity still remains urgent. In this work, a scrupulous design of OER electrode with a unique sandwich‐like coaxial structure of the three‐dimensional Ni@[Ni^(2+/3+)Co₂(OH)_6–7]_x nanotube arrays (3D NNCNTAs) is reported. A Ni nanotube array with open end is homogeneous coated with Ni and Co co‐hydroxide nanosheets ([Ni^(2+/3+)Co₂(OH)_6–7]_x) and is employed as multifunctional interlayer to provide a large surface area and fast electron transport and support the outermost [Ni^(2+/3+)Co₂(OH)_6–7]_x layer. The remarkable features of high surface area, enhanced electron transport, and synergistic effects have greatly assured excellent OER activity with a small overpotential of 0.46 V at the current density of 10 mA cm^?2 and high stability.     

Fabrication of Nickel–Cobalt Bimetal Phosphide Nanocages for Enhanced Oxygen Evolution Catalysis

Replacement of precious metals with earth‐abundant electrocatalysts for oxygen evolution reaction (OER) holds great promise for realizing practically viable water‐splitting systems. It still remains a great challenge to develop low‐cost, highly efficient, and durable OER catalysts. Here, the composition and morphology of Ni–Co bimetal phosphide nanocages are engineered for a highly efficient and durable OER electrocatalyst. The nanocage structure enlarges the effective specific area and facilitates the contact between catalyst and electrolyte. The as‐prepared Ni–Co bimetal phosphide nanocages show superior OER performance compared with Ni₂P and CoP nanocages. By controlling the molar ratio of Ni/Co atoms in Ni–Co bimetal hydroxides, the Ni_0.6Co_1.4P nanocages derived from Ni_0.6Co_1.4(OH)₂ nanocages exhibit remarkable OER catalytic activity (η = 300 mV at 10 mA cm^?2) and long‐term stability (10 h for continuous test). The density‐functional‐theory calculations suggest that the appropriate Co doping concentration increases density of states at the Fermi level and makes the d‐states more close to Fermi level, giving rise to high charge carrier density and low intermedia adsorption energy than those of Ni₂P and CoP. This work also provides a general approach to optimize the catalysis performance of bimetal compounds.     

Water Dissociation Kinetic-Oriented Design of Nickel Sulfides via Tailored Dual Sites for Efficient Alkaline Hydrogen Evolution

The reaction kinetics of alkaline hydrogen evolution reactions (HER) is a trade-off between adsorption and desorption for intermediate species (H₂O, OH, and H_ads). However, due to the complicated correlation between the intermediates adsorption energy and electronic states, targeted regulating the adsorption energy at the atomic level is not comprehensive. Herein, nonmetals (B, N, O, and F) are used to modulate the adsorption energy and electronic structure of Ni₃S₄, and propose that H₂O and OH adsorption energy are correlate directly with d-band center (ε_d) of transition metal Ni, and H_ads adsorption energy has a linear dependence on p-band center (ε_p) of nonmetal S. Direct experimental evidence is offered that in all nonmetals doping samples, Tafel slope and exchange current density can be improved regularly with the ε_d and ε_p, and F-Ni₃S₄ shows the optimum activity with tiny overpotential 29 and 92 mV for harvesting current density 10 and 100 mA cm⁻², respectively. Furthermore, the micro-kinetics analysis and density functional theory calculations verify that F-doping can efficiently reduce the energy barrier of the Volmer step, eventually accelerating the HER kinetics. This work provides atomic-level insight into the structure-properties relationship, and opens an avenue for kinetic-oriented design of alkaline HER and beyond.     

Sodium‐Ion Batteries: Building Effective Layered Cathode Materials with Long‐Term Cycling by Modifying the Surface via Sodium Phosphate

Surface stabilization of cathode materials is urgent for guaranteeing long‐term cyclability, and is important in Na cells where a corrosive Na‐based electrolyte is used. The surface of P2‐type layered Na_2/3[Ni_1/3Mn_2/3]O₂ is modified with ionic, conducting sodium phosphate (NaPO₃) nanolayers, ≈10 nm in thickness, via melt‐impregnation at 300 °C; the nanolayers are autogenously formed from the reaction of NH₄H₂PO₄ with surface sodium residues. Although the material suffers from a large anisotropic change in the c‐axis due to transformation from the P2 to O2 phase above 4 V versus Na⁺/Na, the NaPO₃‐coated Na_2/3[Ni_1/3Mn_2/3]O₂/hard carbon full cell exhibits excellent capacity retention for 300 cycles, with 73% retention. The surface NaPO₃ nanolayers positively impact the cell performance by scavenging HF and H₂O in the electrolyte, leading to less formation of byproducts on the surface of the cathodes, which lowers the cell resistance, as evidenced by X‐ray photoelectron spectroscopy and time‐of‐flight secondary‐ion mass spectroscopy. Time‐resolved in situ high‐temperature X‐ray diffraction study reveals that the NaPO₃ coating layer is delayed for decomposition to Mn₃O₄, thereby suppressing oxygen release in the highly desodiated state, enabling delay of exothermic decomposition. The findings presented herein are applicable to the development of high‐voltage cathode materials for sodium batteries.     

Lanthanide Ion Codoped Emitters for Tailoring Emission Trajectory and Temperature Sensing

A series of lanthanide metal‐organic frameworks (Ln‐MOFs) are synthesized through solvothermal conditions with 1,3‐bis(4‐carboxyphenyl)imidazolium (H₂L). Owing to the lanthanide contraction effect, two different types of Ln‐MOFs, namely, {[Ln(L)₂(OH)]·3H₂O}_n (Ln:Pr, Nd, Sm) and {[Ln(L)₂(COO)(H₂O)₂]·H₂O}_n (Ln: Eu, Gd, Tb, Dy, Tm, Yb, Y), and their corresponding codoped Ln‐MOFs Eu_xTb_1‐xL are obtained. With careful adjustment of the relative concentration of the lanthanide ions and the excitation wavelength, the color of the luminescence can be systematically modulated and white light emission can be further successfully achieved. Furthermore, by virtue of the temperature‐dependent luminescent behavior, Eu_0.2Tb_0.8L allows for the design of a thermometer with an excellent linear response to temperature over a wide range, from 40 to 300 K. This work highlights the practical applications of Ln‐MOFs for tailoring fluorescent color and even obtaining practical white light emission, and especially for sensing temperature as luminescent thermometers in a single framework by controlling in different ways.     

The Synergistic Activation of Ce-Doping and CoP/Ni3P Hybrid Interaction for Efficient Water Splitting at Large-Current-Density

The high intermediate (H*, OH*) energy barriers and slow mass/charge transfer increase the overpotential of alkaline water electrolysis at large-current-density. Engineering the electronic structure with the morphology of the catalyst to reduce energy barriers and improve mass/charge transportation is effective but remains challenging. Herein, a Ce-doped CoP nanosheet is hybrid with Ni₃P@NF (Ni foam) support to enhance mass/charge transfer, tune energy barriers, and improve water-splitting kinetics through a synergistic activation. The engineered Ce_0.2-CoP/Ni₃P@NF cathode exhibits an ultralow overpotential (η₅₀₀, η₁₀₀₀) of −185, and −225 mV at −500 and −1000 mA cm⁻² in 1.0 m  KOH, along with an excellent pH-universality. Impressively, an electrolyzer using the Ce_0.2-CoP/Ni₃P@NF cathode can afford 500 mA cm⁻² at a cell voltage of only 1.775 V and maintain stable electrolysis for 200 h in 25 wt% KOH (50 °C). Characterization and density functional theory calculation further reveal the Ce-doping and CoP/Ni₃P hybrid interaction synergistically downshift d-band centers (ε_d = −2.0 eV) of Ce_0.2-CoP/Ni₃P to the Fermi level, thereby activate local electronic structure for accelerating H₂O dissociation and optimizing Gibbs free energy of hydrogen adsorption (∆G_H*).     

Mesoporous Co3O4 and CoO@C Topotactically Transformed from Chrysanthemum‐like Co(CO3)0.5(OH)·0.11H2O and Their Lithium‐Storage Properties

In this work, a novel hydrothermal route is developed to synthesize cobalt carbonate hydroxide, Co(CO₃)_0.5(OH)·0.11H₂O. In this method, sodium chloride salt is utilized to organize single‐crystalline nanowires into a chrysanthemum‐like hierarchical assembly. The morphological evolution process of this organized product is investigated by examining different reaction intermediates during the synthesis. The growth and thus the final assembly of the Co(CO₃)_0.5(OH)·0.11H₂O can be finely tuned by selecting preparative parameters, such as the molar ratio of the starting chemicals, the additives, the reaction time and the temperature. Using the flower‐like Co(CO₃)_0.5(OH)·0.11H₂O as a solid precursor, quasi‐single‐crystalline mesoporous Co₃O₄ nanowire arrays are prepared via thermal decomposition in air. Furthermore, carbon can be added onto the spinel oxide by a chemical‐vapor‐deposition method using acetylene, which leads to the generation of carbon‐sheathed CoO nanowire arrays (CoO@C). Through comparing and analyzing the crystal structures, the resultant products and their high crystallinity can be explained by a sequential topotactic transformation of the respective precursors. The electrochemical performances of the typical cobalt oxide products are also evaluated. It is demonstrated that tuning of the surface texture and the pore size of the Co₃O₄ products is very important in lithium‐ion‐battery applications. The carbon‐decorated CoO nanowire arrays exhibit an excellent cyclic performance with nearly 100% capacity retention in a testing range of 70 cycles. Therefore, this CoO@C nanocomposite can be considered to be an attractive candidate as an anode material for further investigation.     

Photoinduced Magnetization with a High Curie Temperature and a Large Coercive Field in a Co‐W Bimetallic Assembly

The crystal structure, magnetic properties, and temperature‐ and photoinduced phase transition of [{Co^II(4‐methylpyridine)(pyrimidine)}₂{Co^II(H₂O)₂}{W^V(CN)₈}₂]·4H₂O are described. In this compound, a temperature‐induced phase transition from the Co^II (S = 3/2)‐NC‐W^V(S = 1/2) [high‐temperature (HT)] phase to the Co^III(S = 0)‐NC‐W^IV(S = 0) [low temperature (LT)] phase is observed due to a charge‐transfer‐induced spin transition. When the LT phase is irradiated with 785 nm light, ferromagnetism with a high Curie temperature (T_C) of 48 K and a gigantic magnetic coercive field (H_c) of 27 000 Oe are observed. These T_C and H_c values are the highest in photoinduced magnetization systems. The LT phase is optically converted to the photoinduced phase, which has a similar valence state as the HT phase due to the optically induced charge‐transfer‐induced spin transition.     

Multifunctional Microporous MOFs Exhibiting Gas/Hydrocarbon Adsorption Selectivity,Separation Capability and Three‐Dimensional Magnetic Ordering

Microporous materials [M₃(HCOO)₆] · DMF (M = Mn, Co, Ni) were synthesized solvothermally and structurally characterized by single crystal and powder X‐ray diffraction methods. The metal network exhibits diamondoid connectivity and the overall framework gives rise to zigzag channels along the b axis where guest dimethylformamide molecules reside. The effective pore size of these channels is ～5–6 Å. The materials feature high thermal stability and permanent porosity with relatively small pore diameters which are attributed to the extensive strong dative bonding between the metal centers and formate molecules. The title compounds exhibit interesting multi‐fold gas adsorption and magnetic properties. The adsorption study of a series of alcohols, aromatics, and linear hydrocarbons revealed strong control of the adsorbent channel structures on their adsorption capacity and selectivity. The study also indicated possibility of using these materials for separation of close boiling chemicals (e.g., ethylbenzene and p‐xylene) via pressure swing adsorption (PSA) process and molecules with different diffusion parameters via kinetic‐based process. Three‐dimensional spontaneous magnetic ordering was found in all three network structures investigated and at ground states they behave somewhat like soft magnets.     

Coupling Piezocatalysis and Photocatalysis in Bi4NbO8X (X = Cl,Br) Polar Single Crystals

Reactive oxygen species (ROS) as green oxidants are of great importance for environmental and biological applications. Photocatalysis is one of the major routes for ROS evolution, which is seriously restricted by rapid charge recombination. Herein, piezocatalysis and photocatalysis (i.e., piezo–photocatalysis) are coupled to efficiently produce superoxide radicals (?O₂^?), hydrogen peroxide (H₂O₂), and hydroxyl radicals (?OH) via oxygen reduction reaction (ORR), by using Bi₄NbO₈X (X = Cl, Br) single crystalline nanoplates. Significantly, the piezo‐photocatalytic process leads to the highest ORR performance of the Bi₄NbO₈Br nanoplates, exhibiting ?O₂^?, H₂O₂, and ?OH evolution rates of 98.7, 792, and 33.2 µmol g^?1 h^?1, respectively. The formation of a polarized electric field and band bending allows directional separation of charge carriers, promoting the catalytic activity. Furthermore, the reductive active sites are found enriched on all the facets in the piezo–photocatalytic process, also contributing to the ORR. By piezo–photodeposition of Pt to artificially plant reductive reactive sites, the Bi₄NbO₈Br plates demonstrate largely enhanced photocatalytic H₂ production activity with a rate of 203.7 µmol g^?1 h^?1. The present work advances piezo–photocatalysis as a new route for ROS generation, but also discloses the potential of piezo–photocatalytic active sites enriching for H₂ evolution.     

Hydroxide‐Membrane‐Coated Pt3Ni Nanowires as Highly Efficient Catalysts for Selective Hydrogenation Reaction

Rational design of effective catalysts with both high activity and selectivity is highly significant and desirable for hydrogenation reaction. In this paper, for the first time an efficient approach to controllably construct 1D metal nanowires (NWs) coated with hydroxide (Ni_xM(OH)₂ (M = Mn, Fe, Co, Cu, and Al)) membranes as highly active and selective hydrogenation catalysts is reported. The optimized Ni₃₂Cu(OH)₂ membrane coated Pt₃Ni nanowires show much enhanced selectivity of 87.9% for the hydrogenation of cinnamaldehyde to hydrocinnamaldehyde instead of hydrocinnamyl alcohol, in contrast with the pristine Pt₃Ni nanowires and Pt₃Ni nanowires on Ni(OH)₂ membranes. The enhanced selectivity of Pt₃Ni@Ni₃₂Cu(OH)₂‐2 NWs is ascribed to confinement/poisoning effects of the coated Ni₃₂Cu(OH)₂ membranes as well as the intimate interaction between the Pt₃Ni NWs and Ni₃₂Cu(OH)₂ membranes, as confirmed by X‐ray photoelectron spectroscopy. The coated structures also show good stability after five recycle runs. The present work highlights the importance of surface engineering for the design of multicomponent composites with desirable activity and selectivity toward hydrogenation reaction and beyond.     

The Effect of Methyl Functionalization on Microporous Metal‐Organic Frameworks' Capacity and Binding Energy for Carbon Dioxide Adsorption

The design, synthesis, and structural characterization of two new microporous metal‐organic framework (MMOF) structures is reported; Zn(BDC)(DMBPY)_0.5·(DMF)_0.5(H₂O)_0.5 (1; H₂ BDC = 1,4‐benzenedicarboxylic acid; DMBPY=2,2′‐dimethyl‐4,4′‐bipyridine) and Zn(NDC)(DMBPY)_0.5·(DMF)₂ (2; H₂NDC = 2,6‐naphthalenedicarboxylic acid, DMF=N,N,‐dimethylformamide), which are obtained by functionalizing a pillar ligand with methyl groups. Both compounds are 3D porous structures of the Zn₂(L)₂(P) type and are made of a paddle‐wheel Zn₂(COO)₄ secondary building unit (SBU), with the dicarboxylate and DMBPY as linker (L) and pillar (P) ligands, respectively. Comparisons are made to the parent structures Zn(BDC)(BPY)_0.5·(DMF)_0.5(H₂O)_0.5 (3; BPY = 4,4′‐bipyridine) and Zn(NDC)(BPY)_0.5·(DMF)_1.575 (4) to analyze and understand the effect of methyl functionalization. CO₂‐adsorption studies indicate substantially enhanced isosteric heats of CO₂ adsorption (Q_st) for both compounds, as a result of adding methyl groups to the BPY ligand. The CO₂ uptake capacity, however, is affected by two opposing and competing factors: the enhancement due to increased MMOF–CO₂ interactions (higher Q_st values) and detraction due to the surface area and pore‐volume reduction. For 1′ (the guest‐free form of 1), the positive effect dominates, which leads to a significantly higher uptake of CO₂ than that of its parent structure 3′ (the guest‐free form of 3). In 2′ (the guest‐free form of 2), however, the negative effect rules, which results in a slightly lower CO₂ uptake with respect to 4′ (the guest‐free form of 4). All four compounds exhibit a relatively high separation capability for carbon dioxide over other small gases, including CH₄, N₂, and O₂. The separation ratios of CO₂ to O₂ and N₂ (at 298 K and 1 atm) are 39.8 and 23.5 for compound 1′, 57.7 and 40.2 for 2′, 25.7 and 29.5 for 3′, 89.7, and 20.3 for 4′, respectively. IR and Raman spectroscopic characterization of CO₂ interactions with 1′ and 2′ provides indirect support of the importance of the methyl groups in the interaction of CO₂ within these systems.     

Electrochemical Activation of Manganese‐Based Cathode in Aqueous Zinc‐Ion Electrolyte

Low‐cost and highly safe zinc‐manganese batteries are expected for practical energy storage and grid‐scale application. The electrolyte adjustment is further combined to boost their performance output; however, the mechanism behind the electrochemical contrast caused by electrolyte composition remains unclear, which has held back the development of these systems. Hence, new insight into the electrochemical activation of manganese‐based cathodes, which is induced by the aqueous zinc‐ion electrolyte, is provided. The relationship between the desolvation of Zn²⁺ from [Zn(OH₂)₆]²⁺‐solvation shell and the electrolyte/electrode interfacial reaction to form Zn₄SO₄(OH)₆·4H₂O phase or its analogues is established, which is the key for the electrochemical activation. Further electrolyte optimization promotes the cycling stability of Zn/LiMn₂O₄ battery with a long life span over 2000 cycles. This work illuminates the confused direction in exploring electrolyte for zinc‐manganese batteries.     

Microporous Metal–Organic Frameworks with High Gas Sorption and Separation Capacity

The design, synthesis, and structural characterization of two microporous metal–organic framework structures, [M(bdc)(ted)_0.5]·2 DMF·0.2 H₂O (M = Zn ( 1 ), Cu ( 2 ); H₂bdc = 1,4‐benzenedicarboxylic acid; ted = triethylenediamine; DMF: N,N‐dimethylformamide) is reported. The pore characteristics and gas sorption properties of these compounds are investigated at cryogenic temperatures, room temperature, and higher temperatures by experimentally measuring argon, hydrogen, and selected hydrocarbon adsorption/desorption isotherms. These studies show that both compounds are highly porous with a pore volume of 0.65 ( 1 ) and 0.52 cm³ g^{– 1} ( 2 ). The amount of the hydrogen uptake, 2.1 wt % ( 1 ) and 1.8 wt % ( 2 ) at 77 K (1 atm; 1 atm = 101 325 Pa), places them among the group of metal–organic frameworks (MOFs) having the highest H₂ sorption capacity. [Zn(bdc)(ted)_0.5]·2 DMF·0.2 H₂O adsorbs a very large amount of hydrocarbons, including methanol, ethanol, dimethylether (DME), n‐hexane, cyclohexane, and benzene, giving the highest sorption values among all metal–organic based porous materials reported to date. In addition, these materials hold great promise for gas separation.     

Visible‐Light Excited Luminescent Thermometer Based on Single Lanthanide Organic Frameworks

Isostructural lanthanide organic frameworks (Me₂NH₂)₃[Ln₃(FDC)₄(NO₃)₄]·4H₂O (Ln = Eu ( 1 ), Gd ( 2 ), Tb ( 3 ), H₂FDC = 9‐fluorenone‐2,7‐dicarboxylic acid), synthesized under solvothermal conditions, feature a Ln‐O‐C rod‐packing 3D framework. Time‐resolved luminescence studies show that in 1 the energy difference between the H₂FDC triplet excited state (17794 cm^?1) and the ⁵D₀ Eu³⁺ level (17241 cm^?1) is small enough to allow a strong thermally activated ion‐to‐ligand back energy transfer. Whereas the emission of the ligand is essentially constant the ⁵D₀→⁷F₂ intensity is quenched when the temperature increases from 12 to 320 K, rendering 1 the first single‐lanthanide organic framework ratiometric luminescent thermometer based on ion‐to‐ligand back energy transfer. More importantly, this material is also the first example of a metal organic framework thermometer operative over a wide temperature range including the physiological (12‐320 K), upon excitation with visible light (450 nm).     

Microstructure Evolution of Concentration Gradient Li[Ni0.75Co0.10Mn0.15]O2 Cathode for Lithium‐Ion Batteries

Detailed analysis of the microstructural changes during lithiation of a full‐concentration‐gradient (FCG) cathode with an average composition of Li[Ni_0.75Co_0.10Mn_0.15]O₂ is performed starting from its hydroxide precursor, FCG [Ni_0.75Co_0.10Mn_0.15](OH)₂ prior to lithiation. Transmission electron microscopy (TEM) reveals that a unique rod‐shaped primary particle morphology and radial crystallographic texture are present in the prelithiation stage. In addition, TEM detected a two‐phase structure consisting of MnOOH and Ni(OH)₂, and crystallographic twins of MnOOH on the Mn‐rich precursor surface. The formation of numerous twins is driven by the lattice mismatch between MnOOH and Ni(OH)₂. Furthermore, the twins persist in the lithiated cathode; however, their density decrease with increasing lithiation temperature. Cation disordering, which influences cathode performance, is observed to continuously decrease with increasing lithiation temperature with a minimum observed at 790 °C. Consequently, lithiation at 790 °C (for 10 h) produced optimal discharge capacity and cycling stability. Above 790 °C, an increase in cation disordering and excessive coarsening of the primary particles lead to the deterioration of electrochemical properties. The twins in the FCG cathode precursor may promote the optimal primary particle morphology by retarding the random coalescence of primary particles during lithiation, effectively preserving both the morphology and crystallographic texture of the precursor.     

Magnetic Cores with Porous Coatings: Growth of Metal‐Organic Frameworks on Particles Using Liquid Phase Epitaxy

A novel method for the homogeneous coating of magnetic nanoparticles with metal organic frameworks (MOFs) is reported. Using a liquid phase epitaxy process, a well‐defined number of [Cu₃(btc)₂]nH₂O, HKUST‐1, layers are grown on COOH terminated silica magnetic beads. The structure and porosity of the deposited MOF coatings are studied using X‐ray diffraction and BET analysis. In addition, size and shape of the fabricated composites are analyzed by transmission electron microscopy. Potential applications of particle based MOF films include catalytic coatings and chromatographic media.     

Spin‐Coated Periodic Mesoporous Organosilica Thin Films—Towards a New Generation of Low‐Dielectric‐Constant Materials

Periodic mesoporous organosilica (PMO) thin films have been produced using an evaporation‐induced self‐assembly (EISA) spin‐coating procedure and a cationic surfactant template. The precursors are silsesquioxanes of the type (C₂H₅O)₃Si–R–Si(OC₂H₅)₃ or R′–[Si(OC₂H₅)₃]₃ with R = methene (–CH₂–), ethylene (–C₂H₂–), ethene (–C₂H₄–), 1,4‐phenylene (C₆H₄), and R′ = 1,3,5‐phenylene (C₆H₃). The surfactant is successfully removed by solvent extraction or calcination without any significant Si–C bond cleavage of the organic bridging groups R and R′ within the channel walls. The materials have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X‐ray diffraction (PXRD), and ²⁹Si and ¹³C magic‐angle spinning (MAS) NMR spectroscopy. The d‐spacing of the PMOs is found to be a function of R. Nanoindentation measurements reveal increased mechanical strength and stiffness for the PMOs with R = CH₂ and C₂H₄ compared to silica. Films with different organic‐group content have been prepared using mixtures of silsesquioxane and tetramethylorthosilicate (TMOS) precursors. The dielectric constant (k) is found to decrease with organic content, and values as low as 1.8 have been measured for films thermally treated to cause a “self‐hydrophobizing” bridging‐to‐terminal transformation of the methene to methyl groups with concomitant loss of silanols. Increasing the organic content and thermal treatment also increases the resistance to moisture adsorption in 60 and 80 %‐relative‐humidity (RH) environments. Methene PMO films treated at 500 °C are found to be practically unchanged after five days exposure to 80 % RH. These low dielectric constants, plus the good thermal and mechanical stability and the hydrophobicity suggest the potential utility of these films as low‐k layers in microelectronics.