FE Nodes Research Articles

Dual-Metal-Site Metal-Organic Frameworks for Oxygen Reduction: The Crucial Role of Environmental Species Covering on the Secondary Site.

Macrocycle-based dual-metal-site metal-organic frameworks emerge as promising catalysts whose activity can be conveniently manipulated via metal node modification. However, how the metal node affects catalysis remains unclear. Herein, using first-principles calculations, we provide new mechanistic insight into dual-metal-site catalysis, where the recently synthesized M1-CoOAPc materials (M1 = Co, Ni, Cu; OAPc = octaaminophthalocyanine) are adopted for demonstration. The modeling results explain experimental measurements of Ni- and Cu-CoOAPc for facilitating oxygen reduction while highlighting a contradiction between the theoretical and experimental activity of Co-CoOAPc. Remarkably, this contradiction is attributed to the inherent H2O adsorption on Co nodes, which is usually neglected in dual-metal-site studies. We expand M1-CoOAPc with other metal nodes and find that Fe-CoOAPc (involving *H2O on the Fe nodes) exhibits a desirable theoretical half-wave potential of 0.82 V, as revealed from constant-potential and microkinetic modeling. This work improves the understanding of dual-metal-site catalysis by uncovering the impact of environmental species covering on the secondary site.

Trimetallic FeCoNi Metal-Organic Framework with Enhanced Peroxidase-like Activity for the Construction of a Colorimetric Sensor for Rapid Detection of Thiophenol in Water Samples.

In recent years, nanozymes have attracted particular interest and attention as catalysts because of their high catalytic efficiency and stability compared with natural enzymes, whereas how to use simple methods to further improve the catalytic activity of nanozymes is still challenging. In this work, we report a trimetallic metal-organic framework (MOF) based on Fe, Co and Ni, which was prepared by replacing partial original Fe nodes of the Fe-MOF with Co and Ni nodes. The obtained FeCoNi-MOF shows both oxidase-like activity and peroxidase-like activity. FeCoNi-MOF can not only oxidize the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) to its blue oxidation product oxTMB directly, but also catalyze the activation of H2O2 to oxidize the TMB. Compared with corresponding monometallic/bimetallic MOFs, the FeCoNi-MOF with equimolar metals hereby prepared exhibited higher peroxidase-like activity, faster colorimetric reaction speed (1.26-2.57 folds), shorter reaction time (20 min) and stronger affinity with TMB (2.50-5.89 folds) and H2O2 (1.73-3.94 folds), owing to the splendid synergistic electron transfer effect between Fe, Co and Ni. Considering its outstanding advantages, a promising FeCoNi-MOF-based sensing platform has been designated for the colorimetric detection of the biomarker H2O2 and environmental pollutant TP, and lower limits of detection (LODs) (1.75 μM for H2O2 and 0.045 μM for TP) and wider linear ranges (6-800 μM for H2O2 and 0.5-80 μM for TP) were obtained. In addition, the newly constructed colorimetric platform for TP has been applied successfully for the determination of TP in real water samples with average recoveries ranging from 94.6% to 112.1%. Finally, the colorimetric sensing platform based on FeCoNi-MOF is converted to a cost-effective paper strip sensor, which renders the detection of TP more rapid and convenient.

Enhanced Co-Adsorption of Alcohols and Amines for Visible Light Driven Oxidative Condensation Using Iron-Based MOF.

Imines are essential intermediates in organic transformations, and is generally produced by dehydrogenative condensation of alcohols and amines with the assist of specialized catalysts and additives. Heterogeneous photocatalysis provides a sustainable platform for such process without the using of toxic oxidants, yet a functionalized photocatalyst with optimized co-adsorption of reactants needs to be developed to promote the stoichiometric oxidative condensation under ambient conditions. Here, we show that benzyl alcohol and aniline adsorb non-interferingly on the Fe node and the linker sites of the MIL-53(Fe) metal organic frameworks (MOFs), respectively. The co-adsorption of both reactants barely influences the reduction of molecular oxygen to generate oxygen radicals, resulting in efficient formation of benzaldehyde under visible light. Additionally, the weak adsorption of water together with surface acidity of the MIL-53(Fe) promote a rapid condensation of benzaldehyde with aniline and the depletion of generated water, achieving an efficient C-N bond creation for a wide range of substrates.

Tailored Metal-Organic Frameworks for Water Purification: Perfluorinated Fe-MOFs for Enhanced Heterogeneous Catalytic Ozonation.

An industrially viable catalyst for heterogeneous catalytic ozonation (HCO) in water purification requires the characteristics of good dispersion of active species on its surface, efficient electron transfer for ozone decay, and maximum active species utilization. While metal-organic frameworks (MOFs) represent an attractive platform for HCO, the metal nodes in the unmodified MOFs exhibit low catalytic activity. Herein, we present a perfluorinated Fe-MOF catalyst by substituting H atoms on the metalated ligands with F atoms (termed 4F-MIL-88B) to induce structure evolution. The Lewis acidity of 4F-MIL-88B was enhanced via the formation of Fe nodes, tailoring the electron distribution on the catalyst surface. As a result of catalyst modification, the rate constant for degradation of the target compounds examined increased by ∼700% compared with that observed for the unmodified catalyst. Experimental evidence and theoretical calculations showed that the modulated polarity and the enhanced electron transfer between the catalyst and ozone molecules contributed to the adsorption and transformation of O3 to •OH on the catalyst surface. Overall, the results of this study highlight the significance of tailoring the metalated ligands to develop highly efficient and stable MOF catalysts for HCO and provide an in-depth mechanistic understanding of their structure-function evolution, which is expected to facilitate the applications of nanomaterial-based processes in water purification.

Development and testing of alginate/C3N4porphyrin bead as a self-initiated Fenton photocatalyst for highly efficient atrazine removal

Fenton reaction has been widely used for efficient treatment of organic wastewater. However, its applications are limited by such key factors as pH < 3. In this study, we developed, tested, and optimized an alginate/C3N4porphyrin bead (C3N4por-SA) as a recyclable photocatalyst in a photocatalysis-self-Fenton process to overcome these limitations. Porphyrin-modified C3N4 (C3N4por) was used as the H2O2 donator, while Fe(III) nodes served as the Fenton reagent. The as-prepared floating alginate/C3N4por bead utilized the light source as a driving force for the catalysis. Under visible light irradiation for 6 h, the model pollutant atrazine was degraded by 70.96 % by the optimized photocatalyst (named as C3N4por-SA-Fe1Ca5), demonstrating better photocatalytic performance than alginate/C3N4 beads. This improvement was attributed to the higher H2O2 yield from C3N4por. The alginate/C3N4por bead showed better photocatalytic activity even after several consecutive cycles and could easily be recovered for reuse. Furthermore, Fe(III)/Ca(II) bimetallic alginate bead exhibited better photocatalytic activity and a higher content of •OH radicals than the Ca(II) monometallic alginate beads, due to the ability of Fe(III) nodes to serve as a Fenton reagent. The influences of light sources, and commonly existing matters (namely SO42−, Cl−, CO32−, NO3−, and humic acid) were investigated. Moreover, the alginate/C3N4por bead demonstrated good photocatalytic performance in a simulated natural environment without the addition of extra H2O2, with an atrazine removal percentage of up to 96.3 % after 3-h irradiation. These findings indicated the great potential of alginate/C3N4por bead in practical applications.

Heterometallic-organic frameworks containing Fe(II) nodes as high-performance anode materials for Li-ion batteries

Heterometallic-organic frameworks containing Fe(II) nodes as high-performance anode materials for Li-ion batteries

A label-free ratiometric fluorescent aptasensor based on a peroxidase-mimetic multifunctional ZrFe-MOF for the determination of tetrodotoxin.

A Fe/Zr bimetal-organic framework (ZrFe-MOF) is utilized to establish a ratiometric fluorescent aptasensor for the determination of tetrodotoxin (TTX). The multifunctional ZrFe-MOF possesses inherent fluorescence at 445nm wavelength, peroxidase-mimetic activity, and specific recognition and adsorption capabilities for aptamers, owing to its organic ligand, and Fe and Zr nodes. The peroxidation of o-phenylenediamine (OPD) substrate generates fluorescent 2,3-diaminophenazine (OPDox) at 555nm wavelength, thus quenching the inherent fluorescence of ZrFe-MOF because of the fluorescence resonance energy transfer (FRET) effect. TTX aptamers, which are absorbed on the material surface without immobilization or fluorescent labeling, inhibit the peroxidase-mimetic activity of ZrFe-MOF. It causes the decreased OPDox fluorescence at 555nm wavelength and the inverse restoration of ZrFe-MOF fluorescence at 445nm wavelength. With TTX, the aptamers specifically bind to TTX, triggering rigid complex release from ZrFe-MOF surface and reactivating its peroxidase-mimetic activity. Consequently, the two fluorescence signals exhibit opposite changes. Employing this ratiometric strategy, the determination of TTX is achieved with a detection limit of 0.027ng/mL and a linear range of 0.05-500ng/mL. This aptasensor also successfully determines TTX concentrations in puffer fish and clam samples, demonstrating its promising application for monitoring trace TTX in food safety.

Pushing the heterometal doping limit while preserving long-lived charge separation in a Ti-based MOF photocatalyst

This study explores the nature, dynamics, and reactivity of the photo-induced charge separated excited state in a Fe3+-doped titanium-based metal organic framework (MOF), xFeMIL125-NH2, as a function of iron concentration. The MOF is synthesized with doping levels x = 0.5, 1 and 2 Fe node sites per octameric Ti-oxo cluster and characterized by powder x-ray diffraction, UV-vis diffuse reflectance, atomic absorption, and steady state Fe K-edge X-ray absorption spectroscopy. For each doping level, time-resolved X-ray transient absorption spectroscopy studies confirm the electron trap site role of the Fe sites in the excited state. Time scan data reveal multiexponential decay kinetics for the charge recombination processes which extend into the microsecond range for all three concentrations. A series of dye photodegradation studies, based on the oxidative decomposition of Rhodamine B, demonstrates the reactivity of the charge separated excited state and the photocatalytic capacity of these MOF materials compared to traditional heterometal-doped semiconductor photocatalysts.

Introducing Metal–Organic Frameworks to Melt Electrowriting: Multifunctional Scaffolds with Controlled Microarchitecture for Tissue Engineering Applications

AbstractScaffolds with multiple advantageous biological and structural properties are still a challenge in the field of tissue engineering. The convergence of advanced fabrication techniques and functional materials is key to fulfill this need. Melt electrowriting (MEW) is an additive manufacturing technique that enables the fabrication of microfibrous scaffolds with precisely defined microarchitectures. Here, it is proposed to exploit metal–organic frameworks (MOFs) to efficiently introduce multifunctionalities by combining polycaprolactone (PCL), the gold standard material in MEW, with a silver‐/silver‐chloride‐decorated iron‐based MOF (NH2‐MIL‐88B(Fe)). This results in highly ordered constructs with antibacterial properties and magnetic resonance imaging (MRI) visibility. Scaffolds with up to 20 wt% MOF are successfully melt‐electrowritten with a fiber diameter of 50 µm. Among these, 5 wt% MOF proves to be the optimal concentration as it exhibits silver‐induced sustained antibacterial efficacy while maintaining PCL cytocompatibility and in vitro immune response. The iron component of the MOF (Fe(III) nodes) renders the composite visible with MRI, thereby enabling scaffold monitoring upon implantation with a clinically accepted method. The combination of MEW and MOFs as tunable additives and cargo carriers opens the way for designing advanced multifunctional scaffolds with a wide range of applications in, e.g., tissue engineering, biosensing and drug delivery.

Graphitic carbon nitride membranes intercalated with nano-sized Fe-MOF for enhanced water purification via synergistic separation and Fenton-like processes

Versatile two-dimensional nanomaterials have offered a promising prospect to enhance the water purification efficiency and overcome the fouling obstacle in membrane technology. In this work, a graphitic carbon nitride (g-C3N4) nanosheet membrane intercalated with the nano-sized Fe-based metal-organic framework (MIL-100(Fe)) is developed for the enhanced removal of aqueous organic contaminants by synergically promoting separation and Fenton-like processes. The g-C3N4/MIL-100(Fe) membrane is constructed through a self-assembly route in which the nano-MIL-100(Fe) is anchored into g-C3N4 layers by the coordination bonds between Fe nodes and pyridinic N. The MIL-100(Fe) intercalation not only enlarges the interlayer spacing to raise the membrane permeability, but also expedites the electron transfer between Fe2+ and Fe3+ to improve the Fenton-like activity. With a stable water flux of 98.2 L m2·h−1·bar−1 under wide-range pH and pressures, the g-C3N4/MIL-100(Fe) membrane shows high dye removal efficiency (≥99%) and prominent self-cleaning ability. Mechanism insight proposes a combination of size exclusion, electrostatic interaction and steady radical generation. The intercalation of nano-MIL-100(Fe) into g-C3N4 membranes can realize the mutual promotion between separation and Fenton-like processes, the synergistic effect of which provides an effective and feasible strategy for aqueous pollution abatement.

Selective SERS identification and quantification of glucose enantiomers on homochiral MOFs based enzyme-free nanoreactors

Enantiomeric identification plays a critical role in diverse fields ranging from pharmaceutics, biologics, and stereoselective synthesis to daily life. In this study, an enantioselective surface-enhanced Raman scattering (SERS) substrate was developed by integrating homochiral MIL-101(Fe) with oxidase (GOx)-mimicking Au nanoparticles (Au/Chiral-MIL-101(Fe)) for identification and quantification of chiral molecules. Using L/d-glucose (Glu) as the model enantiomers, the homochiral environment of Au/Chiral-MIL-101(Fe) exhibited selective recognition abilities for Glu enantiomers. The captured Glu was further oxidized to hydrogen peroxide (H2O2) by GOx-like activity of Au nanoparticles. The generated H2O2 molecules reduced Fe(III) nodes in MIL-101(Fe) to Fe(II) for the growth of Prussian blue (PB) on site. Benefitting from the pre-concentrated feature and confinement effect of the porous metal–organic frameworks (MOFs) structure, the Au/Chiral-MIL-101(Fe) hybrid based nanoreactors exhibited high catalytic performance for H2O2 generation and further PB growth, resulting in an excellent sensitivity for Glu quantification. The enantioselective discrimination between l-Glu and d-Glu was directly determined from the intensity of PB signals at 2150 cm−1. Using this sensing strategy, Glu enantiomers could be quantified with a limit of detection (LOD) of 0.09 µM for l-Glu and 0.08 μM for d-Glu. Owing to its enzyme-free nature and universal characteristic for the discrimination of other monosaccharide enantiomers, this design provides an attractive substrate for sensing chiral molecules by Raman technology.

Grafting amino groups to enhance the adsorption of antimonate by MIL-100(Fe) for from natural water: Performance and mechanism

MIL-100(Fe) was modified by amino groups (MIL-100(Fe)-NH2) to enhance the removal of antimonate (Sb(V)) with low concentration (50−200 μg/L) from natural water through batch adsorption experiments. With the initial Sb(V) concentration up to 200 μg/L, the residual Sb(V) concentration after treated by MIL-100(Fe)-NH2 was only 3.52 ± 0.131 μg/L, lower than the drinking water standards (5 μg/L) in China, while that was much higher (94.2 ± 3.52 μg/L) after pristine MIL-100(Fe) treatment. Based on results of XPS analysis, and adsorption kinetics and isotherms, we concluded that Sb(V) substituted the terminal −OH groups of MIL-100(Fe) to form inner-sphere complexes by coordination reactions with Fe nodes and be adsorbed by hydrogen bonding as well. The grafted amino groups (−NH2) adsorbed Sb(V) by hydrogen bonding and facilitated the coordination reactions between Sb(V) and Fe nodes. The higher KL value (0.0116 ± 0.00,118 L/μg) obtained by fitting with the Langmuir isotherm model, while that of unmodified MIL-100(Fe) was 4.74 × 10−4 ± 5.85 × 10−5 L/μg, also confirmed that the −NH2 groups greatly enhanced the affinity between MIL-100(Fe) and Sb(V). Furthermore, MIL-100(Fe)-NH2 still worked nicely in a wide pH range (2 − 12), with varied ionic strength (0.05 µmol/L−1.5 mol/L), coexisting ions (CO32−, NO3−, SO42−, Cl−, H2PO4−), and even in the real water bodies. Additionally, MIL-100(Fe)-NH2 exhibited good reusability and low Fe leaching (99.92 μg/L). We hope MIL-100(Fe)-NH2 become a candidate for effective removal of Sb(V), even other heavy metals from natural waterbodies.

Spectroscopic and reactive characterization of mixed-metal Fe-Cr trimer nodes in metal-organic framework MIL-100.

Metal-organic framework MIL-100 is synthesized featuring heterometallic Fe and Cr M3O nodes where mixing of the metals within the nodes is evidenced using a combination of in situ IR spectroscopy, NO titrations, and CO oxidation kinetics. Reactivity data indicate distinctive properties of the bimetallic nodes.

A sustainable protocol for selective alcohols oxidation using a novel iron-based metal organic framework (MOF-BASU1).

The selective oxidation of active and inactive alcohol substrates is a highly versatile conversion that poses a challenge in controlling the functionality and adjustments on MOFs. On the other hand, it offers an attractive opportunity to expand their applications in designing the next generation of catalysts with improved performance. Herein, a novel iron-based MOF containing sulfonamide (MOF-BASU1) has been fabricated by the reaction of 1,3-benzene disulfonylchloride linker and FeCl3·6H2O. Based on the results, the active surface area of the synthesized MOF is large, which highlights its unique catalytic activity. Optimum conditions were reached after 0.5-2 h, with 15 mg loading of the synthesized MOF under optimal conditions. Furthermore, the turnover frequency was 18-77.6 h-1, which is comparable to values previously reported for this process. Overall, the high catalytic activity observed for MOF-BASU1 might be because of the obtained high surface area and the Lewis acidic Fe nodes. Furthermore, the MOF-BASU1 revealed a remarkable chemoselectivity for aldehydes in the presence of aliphatic alcohols. Overall, the high product yields, facile recovery of nanocatalysts, short reaction times, and broad substrate range make this process environmentally friendly, practical, and economically justified.

Accelerating glucose electrolysis on Cu-doped MIL-88B for an energy efficient anodic reaction in water splitting.

This work reports a promising and sustainable method for valorization of abundantly available biomass feedstocks to overcome the thermodynamic high energy barrier of the OER via glucose electrolysis as a proxy anodic reaction, thereby driving the energy-efficient water splitting for green hydrogen generation. For this, a robust and efficient MIL-88B(Fe) based electrocatalyst is engineered via Cu doping. The ultrasonically prepared Cu-doped@ MIL-88B ink when drop-cast on nickel foam (NF) produces thin nano-porous 2D-sheet like films having a thickness of ca. 300 nm and demonstrates an excellent glucose oxidation reaction (GOR) with a lower potential of 1.35 V versus RHE at 10 mA cm-2. In addition, this electrode shows outstanding long-term electrochemical durability for 50 h and exhibits the maximum GOR current load of 350 mA cm-2 at 1.48 V vs. RHE, while the pristine MIL-88B based electrode exhibits a current load of only 180 mA cm-2 at the same potential bias. The remarkably higher current density after doping indicates an accelerated GOR, which is ascribed to the electronic structure modulation of the Fe nodes by Cu, thereby enhancing the active sites and charge transport characteristics of the frameworks. Most importantly, the MOF-based electrodes demonstrate the occurrence of the GOR prior to the OER at a large potential difference, hence assisting the energy-efficient water splitting for green hydrogen production.

Transformation of Organonitrogen‐Encapsulated MOFs into N‐Doped Fe3O4@C Nanopolyhedron via CVD Super‐Assembly for Photochemical Oxidation

AbstractDevelopment of nano‐structured metal oxides/heteroatom composites with controlled components and structure for photochemical oxidation still remains a great challenge. Here, a new and versatile strategy is reported for transformation of organonitrogen‐encapsulated metal‐organic frameworks (MOFs) into N‐doped Fe3O4@C nanopolyhedron by chemical vapor deposition‐induced super‐assembly method. Strong confined interaction between organonitrogen guests (urea, thiourea, melamine, and dimethylimidazole) and Fe nodes of MOFs realizes reconstruction of crystal structure and introduction of N species. With the novel approach, the uniform dispersion of guests and perfect metallic/heteroatom interfacial is obtained. Compared with MOFs‐derived Fe2O3/C, the heteroatom/defect‐to‐metal cluster charge transfer excitations lead N‐doped Fe3O4@C to exhibit more superior activity for photocatalytic oxidation (turn‐over frequencies as high as 3.72 h−1). It demonstrates that the introduction of abundant pyrrole‐N and oxygen vacancies on carbon interface boosts the advance of photo‐generated carrier transfer. The study offers a simple and promising strategy for the design of novel metal oxides/heteroatom composite with adjustable structure and functions.

Rapid evaluation of notch stress intensity factors using the peak stress method with 3D tetrahedral finite element models: Comparison of commercial codes

AbstractThe peak stress method (PSM) allows a rapid application of the notch stress intensity factor (NSIF) approach to the fatigue life assessment of welded structures, by employing the linear elastic peak stresses evaluated by FE analyses with coarse meshes. Because of the widespread adoption of 3D modeling of large and complex structures in the industry, the PSM has recently been boosted by including four‐node and ten‐node tetrahedral elements of Ansys FE software, which allows to discretize complex geometries. In this paper, a Round Robin among eleven Italian Universities has been performed to calibrate the PSM with seven different commercial FE software packages. Several 3D mode I, II and III problems have been considered to investigate the influence of (i) FE code, (ii) element type, (iii) mesh pattern, and (iv) procedure to extrapolate stresses at FE nodes. The majority of the adopted FE software packages present similar values of the PSM parameters, the main source of discrepancy being the stress extrapolation method at FE nodes.

Iron-Based 2D Conductive Metal–Organic Framework Nanostructure with Enhanced Pseudocapacitance

Electrically conductive metal–organic frameworks have emerged as an attractive class of materials for sensing and energy storage applications with unique electronic properties. However, the field lacks structural diversity often because of the limited choices for metal nodes. In this regard, the incorporation of iron species has been desirable due to its rich redox chemistry. Herein, we report an Fe-based two-dimensional (2D) electrically conductive MOF with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP), namely, Fe–HHTP, that shows redox features and mesoporosity. Fe–HHTP exhibits an electrical conductivity of 3.55 × 10–5 S cm–1 despite a large interlayer spacing of ∼6.5 Å due to N,N-dimethylformamide (DMF) coordination on the Fe nodes. Spectroscopic results confirm that Fe–HHTP exhibits a mixed valency of Fe(II)/Fe(III) with Fe(II) being dominant. Fe–HHTP boasts exceptional capacitance and apparent redox activity compared to the previously reported analogues using the same ligand. We envision that Fe–HHTP can be an excellent candidate for applications in chemical sensing and energy storage where discrete redox features are essential.

Mechanochemically Synthesised Flexible Electrodes Based on Bimetallic Metal-Organic Framework Glasses for the Oxygen Evolution Reaction.

The melting behaviour of metal-organic frameworks (MOFs) has aroused significant research interest in the areas of materials science, condensed matter physics and chemical engineering. This work first introduces a novel method to fabricate a bimetallic MOF glass, through melt-quenching of the cobalt-based zeolitic imidazolate framework (ZIF) [ZIF-62(Co)] with an adsorbed ferric coordination complex. The high-temperature chemically reactive ZIF-62(Co) liquid facilitates the formation of coordinative bonds between Fe and imidazolate ligands, incorporating Fe nodes into the framework after quenching. The resultant Co-Fe bimetallic MOF glass therefore shows a significantly enhanced oxygen evolution reaction performance. The novel bimetallic MOF glass, when combined with the facile and scalable mechanochemical synthesis technique for both discrete powders and surface coatings on flexible substrates, enables significant opportunities for catalytic device assembly.

Mechanochemically Synthesised Flexible Electrodes Based on Bimetallic Metal–Organic Framework Glasses for the Oxygen Evolution Reaction

AbstractThe melting behaviour of metal–organic frameworks (MOFs) has aroused significant research interest in the areas of materials science, condensed matter physics and chemical engineering. This work first introduces a novel method to fabricate a bimetallic MOF glass, through melt‐quenching of the cobalt‐based zeolitic imidazolate framework (ZIF) [ZIF‐62(Co)] with an adsorbed ferric coordination complex. The high‐temperature chemically reactive ZIF‐62(Co) liquid facilitates the formation of coordinative bonds between Fe and imidazolate ligands, incorporating Fe nodes into the framework after quenching. The resultant Co–Fe bimetallic MOF glass therefore shows a significantly enhanced oxygen evolution reaction performance. The novel bimetallic MOF glass, when combined with the facile and scalable mechanochemical synthesis technique for both discrete powders and surface coatings on flexible substrates, enables significant opportunities for catalytic device assembly.