Stefan Kaskel

• PhD
• Professor (Full) at TU Dresden

For the first time, a printable, miniaturized, and gate‐controlled electrochemical capacitor‐diode (G‐CAPode) is presented. The heart of the device consists of a recently developed asymmetric electrical double‐layer capacitor system based on selective, size‐dependent ion adsorption. Due to the introduction of a sieving carbon with ultramicroporous...

The lithium sulfur (Li−S) cell chemistry is promising due to the high specific capacity of its active materials resulting in high specific energy cells. In the past years, the number of publications on practical prototype cells have increased, already reporting high specific energies over 400 Wh kg⁻¹ with low electrolyte‐to‐sulfur (E : S) ratios. T...

A unique feature of flexible metal–organic frameworks (MOFs) is their ability to respond dynamically towards molecular stimuli by structural transitions, resulting in pore-opening and closing processes. One of the most intriguing modes is the “gating”, where the material transforms from the dense to the porous state. The conditions required for the...

Metal–organic polyhedra (MOPs) are versatile supramolecular building blocks for the design of highly porous frameworks by reticular assembly because of their diverse geometries, multiple degrees of freedom regarding functionalization, and accessible metal sites. Lipophilic functionalization is demonstrated to enable the rational assembly and crysta...

Carbon dioxide (CO2) is a major greenhouse gas contributing to global warming. Adsorption in porous sorbents offers a promising method for CO2 capture and storage. The zinc‐triazole‐oxalate‐based Calgary framework 20 (CALF‐20) demonstrates high CO2 capacity, low H2O affinity, and low adsorption heat, enabling energy‐efficient and stable performance...

Carbon dioxide (CO2) is a major greenhouse gas contributing to global warming. Adsorption in porous sorbents offers a promising method for CO2 capture and storage. The zinc-triazole-oxalate-based Calgary framework 20 (CALF-20) demonstrates high CO2 capacity, low H2O affinity, and low adsorption heat, enabling energy-efficient and stable performance...

A new approach for the fabrication copper nanoparticles by a wet chemical reduction method is reported. The natural resources arginine as amino compound and several monosaccharides (xylose, ribose, galactose and glucose) react characteristically performing an Amadori rearrangement followed by a Maillard type reaction. This reaction carried out in a...

Iontronic devices link ion-based transport with established electronic systems. Emerging capacitive devices, like CAPode and G-Cap, feature diode-like rectification and transistor-like switching, respectively, through electrochemical capacitor functionality for enhanced energy storage and signal processing in next-generation low-power electronics....

Achieving commercial viability for more sustainable sodium‐ion batteries (SIB) necessitates reducing the environmental impact of production, particularly originating from electrode drying and the use of toxic solvents like N‐methyl‐2‐pyrrolidone (NMP). This study presents the dry‐processing of commercial P2‐type Na0.75Ni0.25Fe0.25Mn0.50O2 (NFM) via...

Crystalline and porous 2D poly(arylene vinylene)s (2D PAVs), i.e. vinylene-linked 2D conjugated covalent organic frameworks, represent promising materials for electronic and electrochemical applications. Chemically robust 2D PAVs with strong electron affinity are highly desirable for effective host–guest charge transfer to achieve enhanced device p...

The development of smart materials capable of separating dihydrogen isotopologues has risen recently. Among potential candidates, the flexible MIL‐53 (Al) has been gaining attention due to its structural flexibility providing the so‐called ‘’breathing mechanism’’ that can be useful to separate hydrogen isotopologues selectively. In the present work...

Flexible metal–organic frameworks (MOFs) offer unique opportunities due to their dynamic structural adaptability. This review explores the impact of flexibility on gas adsorption, highlighting key concepts for gas storage and separation. Specific examples demonstrate the principal effectiveness of flexible frameworks in enhancing gas uptake and wor...

The discovery of Negative Gas Adsorption (NGA), its experimental characterization, and the toolbox for systematic understanding are reviewed, along with an outlook on future applications and materials discovery pathways.

Renewable electricity-driven valorisation of glycerol is recognised as an effective and alluring approach to generate high value-added compounds from biomass by-products. Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are promising for electrocatalysis due to their diverse and predictable structures, high electronic conductivity, a...

The catalytic potential of flexible metal–organic frameworks (MOFs) remains underexplored, particularly in liquid‐phase reactions. This study employs MIL‐53(Cr), a prototypical “breathing” MOF capable of structural adaptation via pore size modulation, as a photocatalyst for the dehalogenation of aryl halides. Powder X‐ray diffraction and Pair Distr...

All‐solid‐state batteries (SSB) show great promise for the advancement of high‐energy batteries. To maximize the energy density, a key research interest lies in the development of ultrathin and highly conductive solid electrolyte (SE) layers. In this work, thin and flexible sulfide solid electrolyte membranes are fabricated and laminated onto a non...

Carbon dioxide (CO2) is a major greenhouse gas contributing to global warming. Adsorption in porous sorbents offers a promising method to mitigate CO2 emissions by capturing and storage. The zinc-triazole-oxalate-based metal-organic framework CALF-20 demonstrates high CO2 capacity, low H2O affinity, and low CO2 adsorption heat, enhancing energy eff...

This study presents an innovative operando analysis of lithium‐sulfur (Li/S) multilayer pouch cells, employing a combination of lab‐source and synchrotron x‐ray imaging to investigate sulfur crystallite dissolution and lithium dendrite formation. By integrating advanced X‐ray imaging, impedance spectroscopy, and simultaneous monitoring of temperatu...

Herein we investigate the interaction of the highly porous metal-organic framework DUT-76(Cu) with different C1-C4 hydrocarbons at their boiling points. During adsorption the structure appeared to simply decompose however the true process is a transition into an amorphous phase with a smaller total pore volume. We used a combination of multi cycle...

The catalytic potential of flexible metal‐organic frameworks (MOFs) remains underexplored, particularly in solution‐phase reactions. This study employs MIL‐53(Cr), a prototypical "breathing" MOF capable of structural adaptation via pore size modulation, as a photocatalyst for the dehalogenation of aryl halides. Powder X‐ray diffraction and pair dis...

For the first time a printable, miniaturized and gate-controlled electrochemical capacitor-diode (G-CAPode) is presented. The heart of the device consists of a recently developed asymmetric electrical double-layer capacitor system based on selective, size-depended ion adsorption. Due to the introduction of a sieving carbon with ultramicroporous por...

The G-Cap is an iontronic device that combines features of an electrical double-layer capacitor and a transistor, exhibiting switchable capacitance behavior. This functionality is achieved by introducing a third electrode with larger surface area compared to the electrodes of the working capacitor (W-Cap), allowing reversible ion depletion or injec...

We introduce a new approach to defect engineering in Zr-based metal-organic frameworks (Zr-MOFs), aiming to reduce Zr site valency while preserving high node connectivity. Using a rapid heat treatment (RHT) in humid air, O-vacancies were created in DUT-67 through cluster dehydration. Unlike conventional defect engineering, aimed at creating missing...

Metal-organic polyhedra (MOPs) are versatile supramolecular building blocks for the design of highly porous frame-works by reticular assembly because of their diverse geometries, multiple degrees of freedom regarding functionaliza-tion, and accessible metal sites. Lipophilic functionalization is demonstrated to enable the rational assembly and crys...

The field of bioinspired iontronics, bridging electronic devices and ionic systems, has multiple biological applications. Carbon‐based ultracapacitive devices hold promise for controlling bioactive ions via electric double layers due to their high‐surface‐area and biocompatible porous carbon electrodes. However, the interplay between complex bioact...

Iontronic architectures operate via multiple ions or redox processes mimicking neural systems capable to operate with complex ions and biological transmitters with high energy efficiency. Recently, ultracapacitors have emerged as novel iontronic switchable devices with a high on/off ratio. We propose a novel iontronic device offering flexible contr...

The synthesis of various metal acetylene dicarboxylates (MxADC, M=Cu, Ag, Fe, Co, Ni) via new methods are reported. The previously unknown crystal structures for Ag2ADC and FeADC are presented. The behaviour of the different metal dicarboxylates and their role as graphitization catalysts in a printable highly energetic carbon precursor is investiga...

A high demand for oxide dispersion strengthened (ODS) materials arose in wide fields of application. The electroless plating method has been presented as an elegant way to overcome different surface energies and obtain metal‐plated ceramics. However, copper electroless plating is still performed under harsh conditions with toxic and expensive reage...

Metal‐organic frameworks of the CPO‐27 (MOF‐74) series are known for their high adsorption capacities for nitrogen oxides. On the other hand, significantly varying and partly contradictory results were reported regarding their stability to moisture. This aspect has hampered the use of these MOFs in air filtration applications. Here, we show that th...

We present a newly developed instrument for ²²Na-based positron-annihilation lifetime spectroscopy, designed to facilitate the simultaneous control of temperature, gas atmosphere, and humidity in a single experimental system. The spectrometer operates within a temperature range of 50–480 K and pressures from 10⁻⁶ mbar to 1.5 bars. It features a nov...

The field of bioinspired iontronics, bridging electronic devices and ionic systems, has multiple biological applications. Carbon‐based ultracapacitive devices hold promise for controlling bioactive ions via electric double layers due to their high‐surface‐area and biocompatible porous carbon electrodes. However, the interplay between complex bioact...

Non-planar aromatic molecules are interesting systems for organic electronics and optoelectronics applications due to their high stability and electronic properties. By using scanning tunneling microscopy and spectroscopy, we investigated thianthrene-based molecules adsorbed on Au(111), which are non-planar in the gas phase and the bulk solid state...

Interdigital electrodes were prepared using nanoimprint lithography and piezoelectric inkjet printing. These processes are simpler and more cost‐effective than the industrially used electron beam lithography because of their purely mechanical process step. For the investigation of material dependence, platinum as well as carbon electrodes were fabr...

Capacitive analogues of semiconductor diodes (CAPodes) present a new avenue for energy-efficient and nature-inspired next-generation computing devices. Here, we disclose the generalized concept for bias-direction-adjustable n- and p-CAPodes based on selective ion sieving. Controllable-unidirectional ion flux is realized by blocking electrolyte ions...

The development of environmentally friendly processing techniques is a key requisite for future sustainable battery development. The so-called DRYtraec® process is a solvent-free process developed as a viable approach to replace slurry-based binders by fibrous polymers and produce laminated electrodes with a low carbon footprint. It has been demons...

Lithium-Sulfur-Batteries (LSBs) have been discussed as one of the most promising post-lithium-ion-battery technologies in literature for the last decade due to their high theoretical specific energy of 2600 Wh/kg. However, several drawbacks still exist in case of liquid LSB-concepts, especially cycling stability with low electrolyte excess in combi...

In this work, we developed a direct strategy to fabricate Palladene (i. e. Palladium metallene) aerogels and propose a temperature‐dependent growth mechanism. Besides the typical three‐dimensional networks and wrinkled surface morphologies, the as‐prepared Palladene50 ${{Palladene}_{50}}$ aerogel is endowed with abundant Pd²⁺. The as‐prepared Palla...

Lithium–sulfur batteries with liquid electrolytes are discussed as the most promising post‐lithium‐ion‐battery technology in literature due to their high theoretical specific energy and first prototype cells delivering >470 Wh kg⁻¹. Although several electrolyte and material concepts are developed that partially solve the issue of the so‐called shut...

Lithium‐sulfur batteries (LSBs) are discussed as the most promising post‐lithium‐ion battery technology due to the high theoretical energy density and the cost‐efficient, environmental‐friendly active material sulfur. Unfortunately, LSBs still suffer from several limitations such as cycle life and rate capability. To overcome these issues, the deve...

Stimuli‐responsive physisorbents that undergo reversible structural transformations induced by external stimuli (e.g. light, guests, or heat) offer the promise of utility in gas storage and separation. Whereas reports on guest or light‐responsive sorbents have increased in recent years, we are unaware of reports on sorbents that exhibit both light...

Metal-organic frameworks (MOFs) are highly porous materials composed of organic linkers and inorganic nodes. A subset of MOFs can switch between at least two structures differing significantly in porosity, offering new opportunities for application technologies. However, network topology, micromechanics of building blocks and their hinges, particle...

Neurotransmitters carrying specific chemical information play a key role in the nervous system, which inspires ion‐based devices to mimic biological functions of nervous system, including sensing, transduction, and computing. In this work, the interaction mechanism of zwitterionic amino acids, glycine (Gly), and gamma‐aminobutyric acid (GABA) (two...

Crystal size engineering allows to tailor flexible metal-organic frameworks (MOFs) and achieve new properties. The gating type flexibility of DUT-8(Zn) ([Zn 2 (2,6-ndc) 2 (dabco)], 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]-octane) compound is known...

Structural batteries are multifunctional composites that try to achieve a better overall compromise between mechanical and electrochemical properties. These consist of several components, each with a wide range of materials available for selection. Finding the optimal combination is a complex task due to the large number of possible combinations an...

The approach of multivariate MOFs was used to fine-tune the mechanical properties of the flexible framework DUT-49. In situ XRD, NMR and physisorption studies showed that the partial incorporation of a more rigid linker into DUT-49 framework enables a stabilization of the metastable open pore phase which led to a twofold amplification of the expell...

Flexible metal–organic materials (FMOMs) with stepped isotherms can offer enhanced working capacity in storage applications such as adsorbed natural gas (ANG) storage. Unfortunately, whereas >1000 FMOMs are known, only a handful exhibit methane uptake of >150 cm³/cm³ at 65 atm and 298 K, conditions relevant to ANG. Here, we report a double-walled 2...

The approach of multivariate MOFs was used to fine-tune the mechanical properties of the flexible framework DUT-49. In situ XRD, NMR and physisorption studies showed that the partial incorporation of a more rigid linker into DUT-49 framework enables a stabilization of the metastable open pore phase which led to a twofold amplification of ΔnNGA. Bis...

Stimuli‐responsive physisorbents that undergo reversible structural transformations induced by external stimuli (e.g. light, guests, or heat) offer the promise of utility in gas storage and separation. Whereas reports on guest or light‐responsive sorbents have increased in recent years, we are unaware of reports on sorbents that exhibit both light...

Here we describe the synthesis of a series of 1D anisotropic DUT-5(Al) nanostructures differing by their crystal dimensions and aspect ratio. Very long and monodisperse DUT-5(Al) nanowires (NWs) with length exceeding 6 µm were designed by using graphene oxide (GO) nanoscrolls as structure directing agents while shorter DUT-5(Al) nanorods 50 nm in l...

Recently, electrochemical capacitor diodes (CAPodes) have been introduced as a new type of capacitive diode analogues. This device realizes unidirectional charging of ultracapacitors based on ion sieving mechanisms. Here, a new redox CAPode system is presented in which hydroxide ions react with nickel bismuth sulfide on nickel foam as a battery‐lik...

Synthesis and characterization of DEMOFs (defect-engineered metal–organic frameworks) with coordinatively unsaturated sites (CUSs) for gas adsorption, catalysis, and separation are reported. We use the mixed-linker approach to introduce defects in Cu2-paddle wheel units of MOFs [Cu2(Me-trz-ia)2] by replacing up to 7% of the 3-methyl-triazolyl isoph...

Metal‐Organic Frameworks can be grafted with amines by coordination to metal vacancies to create amine‐appended solid adsorbents, which are being considered as an alternative to using aqueous amine solutions for CO2 capture. In this study, we propose an alternative mechanism that does not rely on the use of neutral metal vacancies as binding sites...

Metal‐Organic Frameworks can be grafted with amines by coordination to metal vacancies to create amine‐appended solid adsorbents, which are being considered as an alternative to using aqueous amine solutions for CO 2 capture. In this study, we propose an alternative mechanism that does not rely on the use of neutral metal vacancies as binding sites...

A liquid precursor for 3D printing ultramicroporous carbons (pore width <0.7 nm) to create a novel in‐plane capacitive‐analog of semiconductor‐based diodes (CAPodes) is presented. This proof‐of‐concept integrates functional EDLCs into microstructured iontronic devices. The working principle is based on selective ion‐sieving, controlling the size of...

Transition metal phosphides (TMPs) are promising anode materials for sodium ion battery, thanks to their high theoretical specific capacities. Nevertheless, they suffer from large volume change and from poor conductivity during prolonged cycling. Here we systematically investigate the role of different kinds of single/multi‐wall carbon nanotubes (S...

Porous covalent organic frameworks (COFs) enable the realization of functional materials with molecular precision. Past research has typically focused on generating rigid frameworks where structural and optoelectronic properties are static. Here we report dynamic two-dimensional (2D) COFs that can open and close their pores upon uptake or removal o...

The stimulus-responsive behavior of coordination networks (CNs), which switch between closed (nonporous) and open (porous) phases, is of interest because of its potential utility in gas storage and separation. Herein, we report two polymorphs of a new square-lattice (sql) topology CN, X-sql-1-Cu, of formula [Cu(Imibz)2]n (HImibz = {[4-(1H-imidazol-...

Metal-organic frameworks (MOFs) stand as pivotal porous materials with exceptional surface areas, adaptability, and versatility. Positron Annihilation Lifetime Spectroscopy (PALS) is an indispensable tool for characterizing MOF porosity, especially micro- and mesopores in both open and closed states. Notably, PALS offers porosity insights independe...

Flexible metal–organic frameworks (MOFs) are a unique class of porous materials that feature stimuli-responsive flexible structures and dynamic structural transformation behaviours. Exhibiting structural changes in response to physical or chemical stimuli creates related functions that can be developed for practical applications. The specific compo...

Dynamic multicomponent metal-organic frameworks, comprising numerous functional groups attached to a flexible backbone, expedite the complexity of coordination chemistry. Both factors, stimuli-responsiveness, and non-homogeneous environ-ments, are pivotal for creating complex systems that bring scientists closer to understanding biological structur...

Hydrogen storage by cryoadsorption on porous materials has the advantages of low material cost, safety, fast kinetics, and high cyclic stability. The further development of this technology requires reliable data on the H2 uptake of the adsorbents, however, even for activated carbons the values between different laboratories show sometimes large dis...

Switching coordination networks (CNs) that reversibly transform between narrow or closed pore (cp) and large pore (lp) phases, though fewer than their rigid counterparts, offer opportunities for sorption-related applications. However, their structural transformations and switching mechanisms remain underexplored at the molecular level. In this stud...

Gated adsorption is one of the unique physical properties of flexible metal–organic frameworks with high application potential in selective adsorption and sensing of molecules. Despite recent studies that have provided some guidelines in understanding and designing structural flexibility for controlling gate opening by chemical modification of the...

We present a new example of rare metal–organic frameworks (MOFs) containing ruthenium inorganic building units (IBUs). Advanced characterization techniques such as three-dimensional electron diffraction and in situ powder X-ray diffraction, performed in parallel with adsorption of various gases and vapors, were used to determine the structure and f...

Lithium-sulfur batteries (Li-S) are promising energy storage technologies. Its high gravimetric energy density, the abundance of sulfur and low costs at high production volume, this battery type is especially applicable for automotive and aerospace applications. In recent years, the number of reported prototype cells has increased, as well as their...

Switchable supercapacitors enable a reversible electrically driven uptake and release of bioactive ions by polarizing nanoporous carbon electrodes. In this work we demonstrate the first example of a bioactive ion-based switchable supercapacitor. Based on choline chloride and nanoporous carbons with defined porosity we unravel the mechanism of physi...

3D printing has attracted much attention in industry and academia because it offers simple, low‐cost, versatile and environmentally‐friendly manufacturing technologies and has been utilized to fabricate flexible electronics like supercapacitors, batteries and sensors. Finding a suitable printable ink is the most challenging task for 3D printing. Ca...

Two tetracarboxylic linkers containing seven‐membered rings are synthesized and utilized in metal–organic framework (MOF) syntheses, leading to the two new compounds DUT‐184 and DUT‐193. The introduced odd angles between carboxylates in a new dihydro‐azepine‐containing linker lead to exotic Zn‐based MOFs: a 3D structure based on two catenated sets...