A High‐Performance Sodium‐Ion Hybrid Capacitor Constructed by Metal–Organic Framework–Derived Anode and Cathode Materials

Sodium‐ion hybrid capacitors (SIHCs) can potentially combine the virtues of high‐energy density of batteries and high‐power output as well as long cycle life of capacitors in one device. The key point of constructing a high‐performance SIHC is to couple appropriate anode and cathode materials, which can well match in capacity and kinetics behavior simultaneously. In this work, a novel SIHC, coupling a titanium dioxide/carbon nanocomposite (TiO₂/C) anode with a 3D nanoporous carbon cathode, which are both prepared from metal–organic frameworks (MOFs, MIL‐125 (Ti) and ZIF‐8, respectively), is designed and fabricated. The robust architecture and extrinsic pseudocapacitance of TiO₂/C nanocomposite contribute to the excellent cyclic stability and rate capability in half‐cell. Hierarchical 3D nanoporous carbon displays superior capacity and rate performance. Benefiting from the merits of structures and performances of anode and cathode materials, the as‐built SIHC achieves a high energy density of 142.7 W h kg^?1 and a high power output of 25 kW kg^?1 within 1–4 V, as well as an outstanding life span of 10 000 cycles with over 90% of the capacity retention. The results make it competitive in high energy and power–required electricity storage applications.     

React‐on‐Demand (RoD) Fabrication of Highly Conductive Metal–Polymer Hybrid Structure for Flexible Electronics via One‐Step Direct Writing or Printing

As a fast prototyping technique, direct writing of flexible electronics is gaining popularity for its low‐cost, simplicity, ultrahigh portability, and ease of use. However, the latest handwritten circuits reported either have relative low conductivity or require additional post‐treatment, keeping this emerging technology away from end‐users. Here, a one‐step react‐on‐demand (RoD) method for fabricating flexible circuits with ultralow sheet resistance, enhanced safety, and durability is proposed. With the special functionalized substrate, a real‐time 3D synthesis of silver plates in microscale is triggered on‐demand right beneath the tip in the water‐swelled polyvinyl alcohol (PVA) coating, forming a 3D metal–polymer hybrid structure of ≈7 µm with one single stroke. The as‐fabricated silver traces show an enhanced durability and ultralow sheet resistance down to 4 mΩ sq^?1 which is by far the lowest sheet resistance reported in literatures achieved by direct writing. Meanwhile, PVA seal small particles inside the film, adding additional safety to this technology. Since neither nanomaterials nor a harsh fabrication environment are required, the proposed method remains low cost, user friendly, and accessible to end users. With little effort, the RoD approach can be extended to various printing systems, offering a particle‐free, sintering‐free solution for high‐resolution, high‐speed production of flexible electronics.     

Transparent Zeolite–Polymer Hybrid Materials with Adaptable Properties

We report here on a simple preparation procedure for highly transparent zeolite‐polymer hybrid materials and polymer covered zeolite L monolayers. Wrapping up zeolites containing, e.g., dye molecules as guest species with alkoxysilane derivatives results in an efficient dispersion of the nano particles into the organic liquid monomer. The following copolymerisation process leads to a hard, insoluble and transparent material containing zeolites. Optical properties such as colour, luminescence, refractive index or photochromism can be adapted by simply changing the type and amount of the guest in the zeolite crystals, while transparency is maintained.     

Hybrid 2D Dual‐Metal–Organic Frameworks for Enhanced Water Oxidation Catalysis

Metal–organic frameworks (MOFs) and MOF‐derived nanostructures are recently emerging as promising catalysts for electrocatalysis applications. Herein, 2D MOFs nanosheets decorated with Fe‐MOF nanoparticles are synthesized and evaluated as the catalysts for water oxidation catalysis in alkaline medium. A dramatic enhancement of the catalytic activity is demonstrated by introduction of electrochemically inert Fe‐MOF nanoparticles onto active 2D MOFs nanosheets. In the case of active Ni‐MOF nanosheets (Ni‐MOF@Fe‐MOF), the overpotential is 265 mV to reach a current density of 10 mA cm^?2 in 1 m KOH, which is lowered by ≈100 mV after hybridization due to the 2D nanosheet morphology and the synergistic effect between Ni active centers and Fe species. Similar performance improvement is also successfully demonstrated in the active NiCo‐MOF nanosheets. More importantly, the real catalytic active species in the hybrid Ni‐MOF@Fe‐MOF catalyst are unraveled. It is found that, NiO nanograins (≈5 nm) are formed in situ during oxygen evolution reaction (OER) process and act as OER active centers as well as building blocks of the porous nanosheet catalysts. These findings provide new insights into understanding MOF‐based catalysts for water oxidation catalysis, and also shed light on designing highly efficient MOF‐derived nanostructures for electrocatalysis.     

Organic–Inorganic Hybrid Nanocomposites Prepared by Means of Sol–Gel Condensation of Bismethacrylatesilanes in Reactive Diluents

A bismethacrylatesilane monomer (BMS) was prepared via selective Michael addition of aminopropyltrimethoxysilane (APTMS) to the acrylate groups of 2‐methacryloyloxyethyl acrylate (ethyleneglycol acrylatemethacrylate, EGAMA). Sol–gel condensation of BMS in triethyleneglycoldimethacrylate (TGDMA) afforded in situ stable methacrylate‐functional nanoparticle dispersions, with average nanoparticle diameter of 3–4 nm, as determined by means of element‐specific transmission electron microscopy (TEM). Condensation in the absence of TGDMA could be achieved without gelation. Viscosities of the resulting nanoparticle dispersions were low, ranging from 12 to 1969 mPa s, shear‐rate‐independent and increased with the nanoparticle fraction, exhibiting hard‐sphere behavior. The nanoparticle dispersions in TGDMA were employed as matrix for the preparation of photocurable acrylic nanocomposites. Mechanical properties such as compressive and flexural strength as well as Young’s moduli (6000 to 8700 MPa) have been determined. Low volume shrinkage was observed upon polymerization. The volume shrinkage depended on the nanofiller fraction.     

Modeling the Metal–Insulator Phase Transition in LixCoO2 for Energy and Information Storage

An electro‐chemomechanical phase‐field model is developed to capture the metal–insulator phase transformation along with the structural and chemical changes that occur in Li_xCoO₂ in the regular operating range of 0.5 < x < 1. Under equilibrium, in the regime of phase coexistence, it is found that transport limitations lead to kinetically arrested states that are not determined by strain‐energy minimization. Further, lithiation profiles are obtained for different discharging rates and the experimentally observed voltage plateau is observed. Finally, a simple model is developed to account for the conductivity changes for a polycrystalline Li_xCoO₂ thin film as it transforms from the metallic phase to the insulating phase and a strategy is outlined for memristor design. The theory can therefore be used for modeling Li_xCoO₂‐electrode batteries as well as low voltage nonvolatile redox transistors for neuromorphic computing architectures.     

Atomic‐Scale CoOx Species in Metal–Organic Frameworks for Oxygen Evolution Reaction

The activity of electrocatalysts strongly depends on the number of active sites, which can be increased by downsizing electrocatalysts. Single‐atom catalysts have attracted special attention due to atomic‐scale active sites. However, it is a huge challenge to obtain atomic‐scale CoO_x catalysts. The Co‐based metal–organic frameworks (MOFs) own atomically dispersed Co ions, which motivates to design a possible pathway to partially on‐site transform these Co ions to active atomic‐scale CoO_x species, while reserving the highly porous features of MOFs. In this work, for the first time, the targeted on‐site formation of atomic‐scale CoO_x species is realized in ZIF‐67 by O₂ plasma. The abundant pores in ZIF‐67 provide channels for O₂ plasma to activate the Co ions in MOFs to on‐site produce atomic‐scale CoO_x species, which act as the active sites to catalyze the oxygen evolution reaction with an even better activity than RuO₂.     

Atomic and Molecular Layer Deposition of Hybrid Mo–Thiolate Thin Films with Enhanced Catalytic Activity

A synthetic route toward hybrid MoS₂‐based materials that combines the 2D bonding of MoS₂ with 3D networking of aliphatic carbon chains is devised, leading to a film with enhanced electrocatalytic activity. The hybrid inorganic–organic thin films are synthesized by combining atomic layer deposition (ALD) with molecular layer deposition (MLD) using the precursors molybdenum hexacarbonyl and 1,2‐ethanedithiol and characterized by in situ Fourier transform infrared spectroscopy, and the resultant material properties are probed by X‐ray photoelectron spectroscopy, Raman spectroscopy, and grazing incidence X‐ray diffraction. The process exhibits a growth rate of 1.3 Å per cycle, with an ALD/MLD temperature window of 155–175 °C. The hybrid films are moderately stable for about a week in ambient conditions, smooth (σ_RMS ≈ 5 Å for films 60 Å thick) and uniform, with densities ranging from 2.2–2.5 g cm^?3. The material is both optically transparent and catalytically active for the hydrogen evolution reaction (HER), with an overpotential (294 mV at ?10 mA cm^?2) superior to that of planar MoS₂. The enhancement in catalytic activity is attributed to the incorporation of organic chains into MoS₂, which induces a morphological change during electrochemical testing that increases surface area and yields high activity HER catalysts without the need for deliberate nanostructuring.     

Massive Anisotropic Thermal Expansion and Thermo‐Responsive Breathing in Metal–Organic Frameworks Modulated by Linker Functionalization

Functionalized metal–organic frameworks (fu‐MOFs) of general formula [Zn₂(fu‐L)₂dabco]_n show unprecedentedly large uniaxial positive and negative thermal expansion (fu‐L = alkoxy functionalized 1,4‐benzenedicarboxylate, dabco = 1,4‐diazabicyclo[2.2.2]octane). The magnitude of the volumetric thermal expansion is more comparable to property of liquid water rather than any crystalline solid‐state material. The alkoxy side chains of fu‐L are connected to the framework skeleton but nevertheless exhibit large conformational flexibility. Thermally induced motion of these side chains induces extremely large anisotropic framework expansion and eventually triggers reversible solid state phase transitions to drastically expanded structures. The thermo‐responsive properties of these hybrid solid–liquid materials are precisely controlled by the choice and combination of fu‐Ls and depend on functional moieties and chain lengths. In principle, this combinatorial approach allows for a targeted design of extreme thermo‐mechanical properties of MOFs addressing the regime between crystalline solid matter and the liquid state.     

Fluorous Metal–Organic Frameworks and Nonporous Coordination Polymers as Low‐κ Dielectrics

A fluorous metal–organic framework [Cu(FBTB)(DMF)] (FMOF‐3) [H₂FBTB = 1,4‐bis(1‐H‐tetrazol‐5‐yl)tetrafluorobenzene] and fluorous nonporous coordination polymer [Ag₂(FBTB)] (FN‐PCP‐1) are synthesized and characterized as for their structural, thermal, and textural properties. Together with the corresponding nonfluorinated analogues lc‐[Cu(BTB)(DMF)] and [Ag₂(BTB)], and two known (super)hydrophobic MOFs, FMOF‐1 and ZIF‐8, they have been investigated as low‐dielectric constant (low‐κ) materials under dry and humid conditions. The results show that substitution of hydrogen with fluorine or fluoroalkyl groups on the organic linker imparts higher hydrophobicity and lower polarizability to the overall material. Pellets of FMOF‐1, FMOF‐3, and FN‐PCP‐1 exhibit κ values of 1.63(1), 2.44(3), and 2.57(3) at 2 × 10⁶ Hz, respectively, under ambient conditions, versus 2.94(8) and 3.79(1) for lc‐[Cu(BTB)(DMF)] and [Ag₂(BTB)], respectively. Such low‐κ values persist even upon exposure to almost saturated humidity levels. Correcting for the experimental pellet density, the intrinsic κ for FMOF‐1 reaches the remarkably low value of 1.28, the lowest value known to date for a hydrophobic material.     

High‐Performance Oxygen Reduction Electrocatalyst Derived from Polydopamine and Cobalt Supported on Carbon Nanotubes for Metal–Air Batteries

The development of nonprecious metal‐based electrocatalysts for the oxygen reduction reaction holds the decisive key to many energy conversion devices. Among several potential candidates, transition metal and nitrogen co‐doped carbonaceous materials are the most promising, yet their activity and stability are still insufficient to meet the needs of practical applications. In this study, a core–shell hybrid electrocatalyst is developed via the self‐polymerization of dopamine and cobalt on carbon nanotubes (CNTs), followed by high‐temperature pyrolysis. The polymer‐derived carbonaceous shell contains abundant structural defects and facilitates the formation of Co? N/C active sites, whereas the graphitic carbon nanotube core provides high electrical conductivity and corrosion resistance. These two components separately fulfill different functionalities, and jointly afford the catalyst with excellent electrochemical performance. In 1 m KOH, Co? N/CNT exhibits a positive half‐wave potential of ≈0.91 V, low peroxide yield of <7%, as well as great stability. When used as the air catalyst of primary Zn–air and Al–air batteries, this hybrid electrocatalyst enables large discharge current density, high peak power density, and prolonged operation stability.     

Lanthanide–Organic Framework Nanothermometers Prepared by Spray‐Drying

Accurate, noninvasive, and self‐referenced temperature measurements at the submicrometer scale are of great interest, prompted by the ever‐growing demands in the fields of nanotechnology and nanomedicine. The thermal dependence of the phosphor's luminescence provides high detection sensitivity and spatial resolution with short acquisition times in, e.g., biological fluids, strong electromagnetic fields, and fast‐moving objects. Here, it is shown that nanoparticles of [(Tb_0.914Eu_0.086)₂(PDA)₃(H₂O)]·2H₂O (PDA = 1,4‐phenylenediacetic acid), the first lanthanide–organic framework prepared by the spray‐drying method, are excellent nanothermometers operating in the solid state in the 10–325 K range (quantum yield of 0.25 at 370 nm, at room temperature). Intriguingly, this system is the most sensitive cryogenic nanothermometer reported so far, combining high sensitivity (up to 5.96 ± 0.04% K^?1 at 25 K), reproducibility (in excess of 99%), and low‐temperature uncertainty (0.02 K at 25 K).     

Stimuli‐Responsive Nucleic Acid‐Based Polyacrylamide Hydrogel‐Coated Metal–Organic Framework Nanoparticles for Controlled Drug Release

The synthesis of doxorubicin‐loaded metal–organic framework nanoparticles (NMOFs) coated with a stimuli‐responsive nucleic acid‐based polyacrylamide hydrogel is described. The formation of the hydrogel is stimulated by the crosslinking of two polyacrylamide chains, P_A and P_B, that are functionalized with two nucleic acid hairpins ( 4 ) and ( 5 ) using the strand‐induced hybridization chain reaction. The resulting duplex‐bridged polyacrylamide hydrogel includes the anti‐ATP (adenosine triphosphate) aptamer sequence in a caged configuration. The drug encapsulated in the NMOFs is locked by the hydrogel coating. In the presence of ATP that is overexpressed in cancer cells, the hydrogel coating is degraded via the formation of the ATP–aptamer complex, resulting in the release of doxorubicin drug. In addition to the introduction of a general means to synthesize drug‐loaded stimuli‐responsive nucleic acid‐based polyacrylamide hydrogel‐coated NMOFs hybrids, the functionalized NMOFs resolve significant limitations associated with the recently reported nucleic acid‐gated drug‐loaded NMOFs. The study reveals substantially higher loading of the drug in the hydrogel‐coated NMOFs as compared to the nucleic acid‐gated NMOFs and overcomes the nonspecific leakage of the drug observed with the nucleic‐acid‐protected NMOFs. The doxorubicin‐loaded, ATP‐responsive, hydrogel‐coated NMOFs reveal selective and effective cytotoxicity toward MDA‐MB‐231 breast cancer cells, as compared to normal MCF‐10A epithelial breast cells.     

Synthesis of Semiconducting Functional Materials in Solution: From II‐VI Semiconductor to Inorganic–Organic Hybrid Semiconductor Nanomaterials

This Feature Article provides a brief overview of the latest development and emerging new synthesis solution strategies for II–VI semiconducting nanomaterials and inorganic‐organic semiconductor hybrid materials. Research on the synthesis of II–VI semiconductor nanomaterials and inorganic–organic hybrid semiconducting materials via solution strategies has made great progress in the past few years. A variety of II–VI semiconductor and a new family of [MQ(L)_0.5] (M = Mn, Zn, Cd; Q = S, Se, Te; L = diamine, deta) hybrid nanostructures can be generated using solution synthetic routes. Recent advances have demonstrated that the solution strategies in pure solvent and a mixed solvent can not only determine the crystal size, shape, composition, structure and assembly properties, but also the crystallization pathway, and act as a matrix for the formation of a variety of different II–VI semiconductor and hybrid nanocomposites with diverse morphologies. These II–VI semiconductor nanostructures and their hybrid nanocomposites display obvious quantum size effects, unique and tunable optical properties.     

EXAFS as Powerful Analytical Tool for the Investigation of Organic–Inorganic Hybrid Materials

The potential and application of X‐ray absorption spectroscopy (XAS) for structural investigations of organic–inorganic hybrid materials, with a special emphasis on systems consisting of inorganic building blocks (clusters) embedded into polymer backbones, is extensively reviewed. In the first part of the paper, the main features of organic–inorganic hybrid materials, their classification, the synthetic approaches for their preparation, and their applications are concisely presented, whereas the particular issues related to their characterization are discussed in more detail. In the second section of the paper, the principles and the theoretical background of the XAS method, including experimental design, data reduction, evaluation, analysis, and interpretation are described and discussed. Examples of potentialities of the method for the short‐range structural investigation of inorganic nanostructures in hybrids are provided, and the state‐of‐the‐art in the field of hybrid materials is reviewed. In the third part, six different case studies belonging to our past and present experience in this field are presented and discussed, with a particular focus on their XAS investigation.     

Preconcentration of Nitroalkanes with Archetype Metal–Organic Frameworks (MOFs) as Concept for a Sensitive Sensing of Explosives in the Gas Phase

Thermal desorption based enrichment is a general concept that can enhance any detection system's sensitivity and selectivity. Given their large interior surface area and chemical versatility, archetype metal–organic frameworks (MOFs) are selected for preconcentration of explosives and their precursors occurring in low concentrations, and are compared to the state‐of‐the‐art sorbent Tenax TA . Applying inverse gas chromatography (iGC), this study shows that several archetype MOFs, namely HKUST‐1 and MIL‐53 , surpass Tenax regarding their specific retention volume for nitromethane, a typical ingredient in improvised explosives. Using linear hydrocarbons as reference probe molecules, the dispersive surface energy is determined for all MOFs along with the specific contribution of the nitro group for HKUST‐1 and ZIF‐8 . Trends from pulse‐chromatographic iGC‐investigations are mostly followed in breakthrough and thermal desorption experiments using a 1000 ppm nitromethane source. In these experiments, HKUST‐1 proves the peak substance, with enrichment factors being 109‐fold higher than for Tenax , followed by MIL‐53 . In case of HKUST‐1 , this factor is successfully reproduced for a 1 ppm concentration scenario. This shows that archetype MOFs can be suitable or even superior candidates for a sensitive sensing of nitroalkane explosives from the gas phase by a concept of preconcentration.     

2D Metal–Organic Framework Nanosheets with Time‐Dependent and Multilevel Memristive Switching

Metal–organic framework (MOF) nanosheets have attracted significant interests for sensing, electrochemical, and catalytic applications. Most significantly, 2D MOF with highly accessible sites on the surface is expected to be applicable in data storage. Here, the memory device is first demonstrated by employing M‐TCPP (TCPP: tetrakis(4‐carboxyphenyl)porphyrin, M: metal) as resistive switching (RS) layer. The as‐fabricated resistive random access memory (RRAM) devices exhibit a typical electroforming free bipolar switching characteristic with on/off ratio of 10³, superior retention, and reliability performance. Furthermore, the time‐dependent RS behaviors under constant voltage stress of 2D M‐TCPP–based RRAMs are systematically investigated. The properties of the percolated conducting paths are revealed by the Weibull distribution by collecting the measured turn‐on time. The multilevel information storage state can be gotten by setting a series of compliance current. The charge trapping assisted hopping is proposed as operation principle of the MOF‐based RRAMs which is further confirmed by atomic force microscopy at electrical modes. The research is highly relevant for practical operation of 2D MOF nanosheet–based RRAM, since the time widths, magnitudes of pulses, and multilevel‐data storage can be potentially set.