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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Effects of Water Vapor on the Reactivity of Aluminosilicates in Vapor-Phase Propanal Aldol Condensation

Aluminosilicate materials have been extensively studied as efficient aldol catalysts for C-C coupling reactions due to their acidic nature, high surface area, thermal stability, and porous structure. This work investigated the impact of water vapor pressure on the catalytic reactivity of aluminosilicates for the aldol condensation of propanal to 2-methyl-2-pentenal (MP). The catalytic performance of amorphous SiO2-Al2O3 (A-Si-Al) and aluminated MCM-41 (Al-MCM-41) for the vapor-phase aldol condensation of propanal was evaluated at 200 degrees C as a function of vapor-phase water content at atmospheric pressure. Our findings demonstrate that co-feeding low water vapor pressures (1-18 kPa) with propanal enhances the rates of MP production at 200 degrees C on A-Si-Al. Conversely, water vapor pressures of 25 kPa result in a decrease in aldol dimer formation rates. The rate of MP production evaluated on Al-MCM-41 also increased in the presence of 5 kPa water compared to anhydrous conditions. Propylamine temperature-programmed desorption analyses revealed an increase in Bronsted acid site density when both catalysts were exposed to water, which likely accounts for the observed enhancement in aldol condensation reactivity under hydrous conditions. Reversibility testing of the water vapor effect under reaction conditions, combined with X-ray diffraction analysis of fresh, spent, and regenerated catalysts, revealed no structural changes in either aluminosilicate upon exposure to water or reaction conditions. The rates of aldol condensation and the impact of water vapor were highly consistent across both materials, suggesting that zeolite crystallinity has minimal influence on the catalytic performance.

acid catalysts↗
DOE OSTI2024

Synergistic Ru Co atomic pair with enhanced activity toward levulinic acid hydrogenation

Development of efficient metal-based catalysts is of great importance for levulinic acid (LA) hydrogenation to γ-valerolactone (GVL). The widely employed Ru-based catalysts are advantageous for H 2 dissociation, however, the steric hindrance for large Ru particles hampers their coordination to C=O moiety in LA, and thereby decreasing the activity. Herein, we report a Ru 1 Co 1 -N-C double single-atom catalyst (DSAC) with synergistic Ru and Co atomic pairs for LA hydrogenation into GVL. The Ru and Co doped zeolitic imidazole frameworks (RuCo-doped ZIF-8) precursor was rationally designed ((Ru+Co)/(Zn+Ru+Co) = 2 at.%), where the Zn node spatially isolates Ru and Co species, expanding the adjacent Ru-Co distance and facilitating the formation of the Ru-Co atomic pair upon pyrolysis, with each atom coordinated with three nitrogen atoms (N 3 -Ru 1 Co 1 -N 3 ). The Ru 1 Co 1 -N-C catalyst exhibits outstanding catalytic activity, with a turnover frequency (TOF) of 1980 h –1 , surpassing previously reported Ru-based catalysts. Experimental investigation and density functional theory (DFT) calculations reveal that the electron-rich Ru induced by less electronegative Co facilitates H 2 dissociation, while atomic Ru in dual-atomic pairs promotes C=O activation, Ru and Co atomic pairs synergistically enhancing LA conversion to GVL. In conclusion, this research will shed light on the precise control of active sites at atomic scale, and also provides a new concept for designing high-performance Ru-based catalysts towards LA hydrogenation to GVL.

Double single-atom catalysts↗
DOE OSTI2025

Quantifying fission gas adsorption onto natural clinoptilolite in the presence of environmental air and water

Adsorption of noble gas fission products onto naturally occurring minerals is of interest for its potential to retain or retard emissions from nuclear fuel reprocessing operations or underground nuclear explosions. However, experimental studies of trace noble gas adsorption in the presence of air and water have largely focused on synthetic materials, such as activated carbon or metal-organic frameworks. Here, in this study, adsorption of Kr and Xe onto the naturally occurring zeolitic mineral clinoptilolite is studied in the presence of nitrogen and water. By varying the composition of the gas phase and monitoring the change in the combined adsorbate mass, the adsorbed concentration of noble gas is calculated gravimetrically. For dry clinoptilolite, the concentration of adsorbed Kr and Xe is linearly correlated with noble gas pressure and Henry's Law appears satisfactory, despite the presence of nitrogen at atmospheric pressures. However, the presence of water significantly reduces the adsorbed concentration of both Kr and Xe, which is typical in nanoporous sorbents. Here, an empirical bivariate model is presented, combining the Henry's Law adsorption model for a dry adsorbent with the exponential reduction in the presence of water, as reported by Lungu and Underhill in 1999. This model provides a means to estimate the adsorbate concentration at the trace partial pressures and higher water contents relevant to field-scale modeling of fission gas transport through the vadose zone.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Efficient SF 6 /N 2 separation at high pressures using a zirconium-based mesoporous metal–organic framework

Adsorptive separation of SF 6 /N 2 mixtures is an important issue since SF 6 is a significant greenhouse gas. Although separation performances should be evaluated under high pressure conditions to find an efficient adsorbent candidate for pressure swing adsorption (PSA) processes, no studies on metal–organic frameworks (MOFs) have focused on SF 6 /N 2 separation at high pressures above 1 bar. In this study, we evaluated the potential of three hydrothermally stable adsorbents, including two MOFs (UiO-66 and UiO-67) and zeolite-13X, for SF 6 /N 2 separation under normal PSA operation pressures (~10 bar). Interestingly, UiO-67 with a high surface area and large pore size exhibited very high SF6/N2 selectivity (30~37) at 10 bar as well as a significantly large SF6 working capacity (5.94 mmol g-1) between 10 bar and 1 bar. Moreover, UiO-67 showed facile regeneration at the ambient temperature as well as good cyclic adsorption and desorption behavior during 20 cycles. These results show that UiO-67 is a potential adsorbent for adsorptive SF 6 /N 2 separation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Influence of metal organic framework glasses on thermoelectric properties of AgSb 0.96 Zn 0.04 Te 2 alloy

In recent years, a significant number of chalcogenides-based thermoelectric (TE) materials have been investigated theoretically and experimentally. However, the efficiency of TE materials is often limited by physical and chemical stability issues. Therefore, it is crucial to identify additive materials that can reduce thermal conductivity and improve the efficiency of crystalline TE materials. One well-known approach to lower thermal conductivity is introducing porosity into the material structure, which helps scatter phonon energy. Metal-organic framework (MOF) crystalline materials, known for their porosity and physical and chemical stability, offer unique advantages in TE applications. In this study, we investigate the influence of 20 weight% amorphous Zeolitic Imidazolate Framework (ZIF)-62 to p-type AgSb 0.96 Zn 0.04 Te 2 (ASTZ), a well-known TE material. We synthesized composites, ASTZ, ASTZ-Zn, and ASTZ-Co, by sintering ASTZ with amorphous ZIF-62(Zn) and ZIF-62(Co) respectively. The addition of amorphous ZIF-62(Zn) leads to a significant enhancement in the Seebeck coefficient of ASTZ increasing from 151 µV/K to 229 µV/K at 586K. Moreover, the thermal conductivity of the ASTZ TE materials drops drastically from 0.491 Wm -1 K -1 to around 0.22 Wm -1 K -1 at 623K with the addition of either amorphous ZIF-62(Zn) or ZIF-62(Co). Remarkably, ASTZ containing amorphous ZIF-62(Zn) achieves a maximum thermoelectric figure of merit (zT max ) of approximately 0.078 at 573K, surpassing any MOF-based thermoelectric material reported to date. In conclusion, these findings highlight the potential of amorphous ZIF-62 as an effective additive for enhancing the properties of thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Compact ammonia reforming at low temperature using catalytic membrane reactors

Ammonia is a leading carrier for the storage and transport of renewable hydrogen, but its deployment requires scalable technologies for efficient decomposition and purification. In this work, we report on the efficient delivery of high purity hydrogen from ammonia decomposition using a catalytic membrane reactor (CMR). Improvements to the electroless plating process reduced the Pd membrane thickness by >35%, resulting in commensurate increases in hydrogen permeance without sacrificing selectivity. To increase throughput a commercial Ru/Al 2 O 3 catalyst was added to the lumen, and the CMR could process ammonia flowrates 10–50 times higher than an equivalent packed bed reactor while maintaining the same level of conversion. It is shown that the earth-abundant zeolite clinoptilolite could reduce ammonia impurities in the permeated H 2 to the levels required by PEM fuel cells (<25 ppb). Performance increased significantly across a >500-h durability test due to improvements in membrane permeability. Finally, the results show that CMRs are a viable technology for distributed production of hydrogen from ammonia.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

CO 2 adsorption mechanisms at the ZIF-8 interface in a Type 3 porous liquid

Porous liquids (PLs) are an attractive material for gas separation and carbon sequestration due to their permanent internal porosity and high adsorption capacity. PLs that contain zeolitic imidazole frameworks (ZIFs), such as ZIF-8, form PLs through exclusion of aqueous solvents from the framework pore due to its hydrophobicity. The gas adsorption sites in ZIF-8 based PLs are historically unknown; gas molecules could be captured in the ZIF-8 pore or adsorb at the ZIF-8 interface. To address this question, ab initio molecular dynamics was used to predict CO 2 binding sites in a PL composed of a ZIF-8 particle solvated in a water, ethylene glycol, and 2-methylimidazole solvent system. Further, the results show that CO 2 energetically prefers to reside inside the ZIF-8 pore aperture due to strong van der Waals interactions with the terminal imidazoles. However, the CO 2 binding site can be blocked by larger solvent molecules that have greater adsorption interactions. CO 2 molecules were unable to diffuse into the ZIF-8 pore, with CO 2 adsorption occurring due to binding with the ZIF-8 surface. Therefore, future design of ZIF-based PLs for enhanced CO 2 adsorption should be based on the strength of gas binding at the solvated particle surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

A pair of metal organic framework (MOF)-derived oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts for zinc-air batteries

Metal organic frameworks (MOFs) are amazing precursors for the development of functional catalysts due to their ability of being modified both structurally and in terms of composition. Here this work presents a pair of MOF - derived oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts for the advancement of zinc-air batteries. Zeolitic imidazolate frameworks (ZIF) are known as ideal materials to create doped carbons. Combining with a sacrificial tellurium template, we have developed a “pseudo-carbon nanotube” with a ZIF-8 that is doped with a mixture of zinc, cobalt, and iron. The resulting mixed-metal doped porous carbon nanotubes (CoFeZn@pCNT) show excellent catalytic activity for ORR with a half-way ORR potential (E 1/2 ) of 0.87 V vs. RHE (reverse hydrogen electrode). Iridium-based catalysts are known as the best option for OER so far, but it is not viable for practical applications due to cost restrictions. Previous research into alternative catalysts has focused on metal oxides with first-row transition metals. Metal sulfides provide superior conductivity compared to metal oxides and are a new frontier in the search for affordable, active, and stable OER catalysts. By combining cobalt, iron, and nickel into a MOF structure (ZIF-67), followed by a sulfurization process, a MOF-derived mixed-metal sulfide catalyst (FeCoNi–S@ZIF) has been developed in this study. The resulting catalysts show an onset OER potential of 1.65 V vs. RHE at 10 mA cm -2 and exhibit remarkable stability for the operation of zinc-air batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Support size regulated ruthenium-sulfoacid-nitrogen sites intensify cellulose hydrogenolysis to 1,2-propylene glycol

Rational design of metal-acid-base multifunctional catalysts for upgrading cellulose to 1,2-propylene glycol (1,2-PG) is of great significance for building a sustainable world. However, it is time-consuming and tedious to regulate metal-acid-base sites to balance major reactions to render a high 1,2-PG yield. We herein report support size simultaneously regulated ruthenium-sulfoacid-nitrogen (Ru–SO 3 H–N) sites for cellulose hydrogenolysis to high yield 1,2-PG. Originated from the depolymerization and reassembly of zinc-1,3,5-benzenetricarboxylic acid (ZnBTC) fiber with zeolitic imidazolate framework (ZIF-8) in water, 2-methylimidazole infiltrated nanorod (ZnBTC(mIM)) with a varied aspect ratio was fabricated by varying the feed ratio of ZIF-8/ZnBTC. Upon being pyrolyzed, sulfonated and impregnated with Ru ions, the supported sites were tailored in terms of Ru single-atom/nanocluster ratio, SO 3 H acidity and N basicity. Further, the elaborately fabricated catalyst delivers 32.3% yield of 1,2-PG, corresponding to a high productivity of 67.71 mol h -1 g Ru -1 and a large turnover number of 34193, two and three orders of magnitude higher than those by using other Ru-containing catalytic systems for cellulose hydrogenolysis. The excellent performance can be attributed to optimized electronic and molecular structure of Ru–SO 3 H–N sites that can improve rate-determining cellulose hydrolysis/fructose hydrogenolysis, pivotal glucose isomerization with others to proceed at a matched rate. This study opens a new avenue to facilely tailor the metal-acid-base sites by rational design of size controlled supporting matrix.

1,2-Propylene glycol↗
DOE OSTI2023

In-field alpha spectrometry system for uranium enrichment verification of uranium hexafluoride

A portable In-Field Alpha Spectrometry (IFAS) system was developed to support on-site uranium enrichment determination for samples taken at facilities working with gaseous UF 6 . It consists of a modified commercial alpha spectrometer, a vacuum pump, a laptop computer, and associated connectors and cables. The IFAS uses specially designed Single-Use Destructive Assay (SUDA) samplers to capture gaseous UF 6 and convert and store it as UO 2 F 2 in a thin-film zeolite. To examine the quantitative performance of the IFAS system a large number of replicate SUDA samples was acquired for natural uranium (NU, 0.72 wt%, 23 samples), low enriched uranium 1 (LEU1, 2.33 wt% 235 U, 10 samples), and low enriched uranium 2 (LEU2, 4.62 wt% 235 U, 10 samples). The standard deviation (SD) values for uranium enrichment determination with the IFAS for NU, LEU1, and LEU2, in 20-hour assays, were 0.037 wt% 235 U, 0.063 wt% 235 U, and 0.072 wt% 235 U, respectively. In addition, a separate analysis suggests that comparable SD values can be achieved in less time, approximately 8-10 hours. For context, these SD values are well below the International Atomic Energy Agency’s International Target Values for the determination of uranium enrichment in non-destructive assay measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Discrepancy quantification between experimental and simulated data of CO 2 adsorption isotherm using hierarchical Bayesian estimation

Here, to quantitatively analyze the inconsistencies commonly observed between experimental and simulated adsorption isotherms, parameter estimation of adsorption isotherm models was conducted by hierarchical Bayesian estimation with parameter uncertainties being quantified as probability distributions. The estimation method was implemented using Markov Chain Monte Carlo (MCMC) to analyze multiple data sets obtained from different sources, including a publicly available database. To describe the discrepancies of experimental and simulated adsorption data, the simulation data was set as the reference to which experimental measurements were compared. We applied the proposed approach to analyze CO 2 adsorption isotherms that are measured and simulated on zeolite 13X and MIL-101(Cr). In these case studies, the discrepancy of CO 2 adsorption isotherm was successfully quantified between experimental measurements and predictions given by molecular simulations using Grand Canonical Monte Carlo (GCMC), where uncertainties were quantified as probability distributions. Furthermore, experimental data sets that agree well with the GCMC simulation have been identified, providing insights into experimental and measurement methods as well as choosing the right assumptions in the molecular simulation.

42 ENGINEERING↗
DOE OSTI2022

Atomic-scale characterization of (electro-)catalysts and battery materials by atom probe tomography

To optimise the performance of heterogeneous (electro-)catalysts and battery electrodes, it is essential to establish the structure-property relationships. This can only be achieved by obtaining a full three-dimensional (3D) characterisation of atomic-scale structure and chemistry of these advanced materials. Atom probe tomography (APT) can provide unique insights into 3D elemental distribution, including low atomic mass elements, with sub-nanometer spatial resolution. Despite its superior chemical analytical capability and spatial resolution, APT has limited applications for sustainable energy materials due to technical and analytical challenges. The recent developments in experimental setups, sample preparation methods and data analysis algorithms have opened the door to the possibility of analysing heterogeneous (electro-)catalysts and battery electrodes. This perspective provides an overview of these developments, exemplified by recent achievements of analyzing model heterogeneous model (electro-)catalysts, nanoparticles, zeolites, MOFs and Li-ion battery electrodes, followed by a discussion of limitations, opportunities, and potentials of APT for future scientific exploration.

atom probe tomography↗
DOE OSTI2024

Advanced Functional Materials ZnO@ZIF-8 Heterostructures for Neuromorphic Synaptic Devices

Metal-Organic Frameworks have shown great promise for memristive synaptic devices because of their adaptable electrical properties and inherent porosity, which help in efficient ion transport and storage of functional molecules. However, the limited conductivity and sensitivity to moisture associated with most MOF materials hinder their use in electronic applications. In this study, MOFs derived from metabolites have been synthesized, using ZnO as a self-sacrificial metallic source to grow Zeolitic Imidazolate Framework-8 (ZIF-8), forming ZnO@ZIF-8 heteronanostructures for neuromorphic applications. These hybrids ZnO@ZIF-8 act as promising candidates for advanced electronic applications. Through systematic investigations, including a comparison of ZnO@ZIF-8 bilayer devices with ZnO single-layer counterparts, a significant discovery emerged. The bilayer synaptic devices outperformed their single layer counterparts in electrical characteristics, as evidenced by Current-Voltage curve analysis and Long-Term Potentiation/Long Term Depression (LTP/LTD) measurements. Additionally, the ZnO layer thickness (10, 30, 50 nm) has been emphasized and the effects of annealing at 300°C in a vacuum were carefully studied for Neuromorphic Synaptic Devices. Remarkably, the 10 nm ZnO layer exhibited the lowest set voltage and a consistent On/Off ratio. This work marks a significant advancement in understanding bilayer synaptic devices, highlighting the crucial role of ZIF-8 in shaping the future of neuromorphic systems

Kolleboyina, Jayaramulu↗
DOE OSTI2023

Crystal structure of calcium L-5-methyltetrahydrofolate trihydrate type I, C 20 H 23 N 7 O 6 Ca(H 2 O) 3

The crystal structure of L-5-methyltetrahydrofolate calcium trihydrate has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Calcium levomefolate trihydrate crystallizes in space group P2 1 2 1 2 1 (#19) with a = 7.1706(6), b = 6.5371(5), c = 53.8357(41) Å, V = 2523.58(26) Å 3 , and Z = 4. The structure is characterized by alternating hydrophobic and hydrophilic layers along the c-axis. The Ca cations are 7-coordinate, and share edges to form chains along the b-axis. Each of the water molecules acts as a donor in two hydrogen bonds. The coordinated water molecule makes two strong intermolecular O–H∙∙∙O hydrogen bonds to carboxyl and carbonyl groups. The two zeolitic water molecules form weaker hydrogen bonds, to carbonyl O atoms, ring N atoms, and aromatic C atoms. Several N–H∙∙∙O/N hydrogen bonds, as well as C–H∙∙∙O hydrogen bonds, also contribute to the lattice energy.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Operando S/TEM Reactions of Pt/TiO 2 Catalysts for Catalytic Fast Pyrolysis

Conversion of lignocellulosic biomass into the transportation fuel is an attractive concept. Using ex situ Catalytic Fast Pyrolysis (CFP) improves to upgrade bio-oils via catalytic deoxygenation of the biomass pyrolysis vapors. Zeolites are often used in this technique as the catalyst; however, in order to reduce minimum fuel selling price and improve carbon yields, ongoing research emphasizes catalyst optimization. By using bifunctional metal-acid catalysts and utilizing hydrogen, it is possible to improve carbon yields by minimizing the carbon-containing light gasses (since oxygen is removed aswater) and by reducing coke formation. Current research and development activities focuses on Pt/TiO 2 catalysts as the most promising catalyst candidates for the hydrodeoxygenation process. Here, our aim is to determine the structure-function relationships of the Pt/TiO 2 catalyst and the role of Pt dispersions within the catalyst on performance, using operando scanning transmission electron microscopy (S/TEM).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

PGM-Free Oxygen-Reduction Catalyst Development for Proton-Exchange Membrane Fuel Cells: Challenges, Solutions, and Promises

Proton-exchange membrane fuel cells (PEMFCs) are efficient and clean hydrogen energy technologies for transportation and stationary applications. Highly active and durable low-cost cathode catalysts for the oxygen-reduction reaction (ORR) under challenging acidic environments are desperately needed to address the cost and durability issues of PEMFCs. The most promising platinum group metal (PGM)-free catalysts for the ORR in acidic media are atomically dispersed and nitrogen-coordinated metal site catalysts denoted as M–N–C, M = Fe, Co, or Mn. Due to significant efforts in the past few decades, these catalysts have demonstrated much-improved ORR activity and promising initial fuel cell performance approaching traditional Pt/C catalysts. However, the insufficient long-term stability (up to 5000 h) under PEMFC operation represents a primary technical barrier to making current PGM-free catalysts less viable yet in PEMFCs. In this Account, we highlight recent advances in synthesizing efficient PGM-free catalysts for the ORR in PEMFCs, emphasizing effective strategies to improve mass and intrinsic activity and the possible degradation mechanisms. In particular, a chemical doping method based on the zeolitic imidazolate framework (ZIF)-8 represents the key to developing efficient M–N–C catalysts containing atomically dispersed and nitrogen-coordinated single metal active sites (i.e., MN 4 ). The newly acquired understanding of the formation mechanism of MN 4 active sites during the thermal activation and its correlation to catalytic properties guide the rational catalyst design rather than relying on current trial-and-error approaches. Considerable efforts have further been invested in increasing the active site density and enhancing intrinsic activity by regulating carbon-phase structures and the local coordination environment. Furthermore, these highly active catalysts usually suffer from significant activity loss during the ORR. Therefore, breaking the activity–stability trade-off is the key to simultaneously achieving activity and stability in one catalyst, which is discussed on the basis of our recent successes in regulating local carbon structures surrounding active single metal sites. Significant research efforts toward understanding the degradation mechanisms and improving the lifetime of PGM-free catalysts are still crucial for viable applications in the future. Novel electrode designing strategies are needed to translate the PGM-free catalysts’ ORR activity to solid-state electrolyte-based membrane electrode assemblies (MEAs) with robust three-phase (i.e., gas–liquid–solid) interfaces for efficient charge and mass transports for performance improvement. On the basis of our effort at the University at Buffalo supported by ElectroCat Consortium associated with U.S. DOE’s Hydrogen and Fuel Cell Technologies Office, we provide a perspective on PGM-free cathode catalysts concerning remaining bottlenecks and future opportunities, aiming to inspire the community in both mechanistic understanding and technological development.

08 HYDROGEN↗
DOE OSTI2024

Fiber Sorbents – A Versatile Platform for Sorption-Based Gas Separations

Increasing demand for high-purity fine chemicals and a drive for process intensification of large-scale separations have driven significant work on the development of highly engineered porous materials with promise for sorption-based separations. While sorptive separations in porous materials offer energy-efficient alternatives to longstanding thermal-based methods, the particulate nature of many of these sorbents has sometimes limited their large-scale deployment in high-throughput applications such as gas separations, for which the necessary high feed flow rates and gas velocities accrue prohibitive operational costs. These processability limitations have been historically addressed through powder shaping methods aimed at the fabrication of structured sorbent contactors based on pellets, beads or monoliths, commonly obtained as extrudates. These structures overcome limitations such as elevated pressure drops commonly recorded across powder adsorption beds but often accrue thermal limitations arising from elevated particle density and aggregation, which ultimately cap their maximum separation performance. Furthermore, the harsh mechanical strain to which powder particles are subjected during contactor fabrication, in the form of extrusion/compression forces, can result in partial pore occlusion and framework degradation, further limiting their performance. Here, we present the development of porous fiber sorbents as an alternative sorbent contactor design capable of addressing sorbent processability limitations while enabling an array of performance-maximizing heat integration capabilities. This new sorbent form factor leverages pre-existing know-how from hollow fiber spinning to produce fiber-shaped sorbent contactors through the phase inversion of known polymers in a process known as dry-jet/wet quenching. The process of phase inversion allows microporous sorbent particles to be latched onto a macroporous polymer matrix under mild processing conditions, thus making it compatible with soft porous materials prone to amorphization under traditional pelletization conditions. Sorbent fibers can be created with different geometries through control of the spinning apparatus and process, offering the possibility to produce monolithic and hollow fibers alike, the latter of which can be integrated with thermalization fluid flows. In this Account, we summarize our progress in the field of fiber sorbents from both design and application standpoints. We further guide the reader through the evolution of this field from the early inceptive work on zeolite hollow fibers to recent developments on MOF fibers. We highlight the versatile nature of fiber sorbents, both from the composition, fabrication and structure points of view, and further demonstrate how fiber sorbents offer alternative paths in tackling new and challenging chemical separation challenges like direct air capture (DAC), with a final perspective on the future of the field.

36 MATERIALS SCIENCE↗