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DOE OSTI2025

Synergistic Tuning of Microstructure and Morphology in Carbon Molecular Sieve Hollow Fibers for Propylene/Propane Separation

Abstract Asymmetric carbon molecular sieve (CMS) hollow fiber membranes with tunable micro‐ and macro‐structural morphologies for energy efficient propylene‐propane separation are reported here. A sub‐glass transition temperature (sub‐Tg) thermal oxidative crosslinking strategy enables simultaneous optimization of the intrinsic molecular sieving properties while also reducing the thickness of the CMS “skin” derived from the 6FDA : BPDA/DAM polyimide precursors. Such synergistic tuning of CMS microstructure and macroscopic morphology of CMS hollow fibers enables significantly increased propylene permeance (reaching 186.5 GPU) while maintaining an appealing propylene/propane selectivity of 13.3 for 50/50 propylene/propane mixed gas feeds. Our findings reveal a more refined and versatile tool than available with previous O 2 ‐doping pretreatments. The advanced approach here should be broadly useful to other polyimide precursors and diverse gas pairs.

Liu, Zhongyun [School of Chemical &amp, Biomolecul↗

DOE OSTI2024

Catalytically Active Site Mapping Realized through Energy Transfer Modeling

Abstract The demands of a sustainable chemical industry are a driving force for the development of heterogeneous catalytic platforms exhibiting facile catalyst recovery, recycling, and resilience to diverse reaction conditions. Homogeneous‐to‐heterogeneous catalyst transitions can be realized through the integration of efficient homogeneous catalysts within porous matrices. Herein, we offer a versatile approach to understanding how guest distribution and evolution impact the catalytic performance of heterogeneous host–guest catalytic platforms by implementing the resonance energy transfer (RET) concept using fluorescent model systems mimicking the steric constraints of targeted catalysts. Using the RET‐based methodology, we mapped condition‐dependent guest (re)distribution within a porous support on the example of modular matrices such as metal–organic frameworks (MOFs). Furthermore, we correlate RET results performed on the model systems with the catalytic performance of two MOF‐encapsulated catalysts used to promote CO 2 hydrogenation and ring‐closing metathesis. Guests are incorporated using aperture‐opening encapsulation, and catalyst redistribution is not observed under practical reaction conditions, showcasing a pathway to advance catalyst recyclability in the case of host–guest platforms. These studies represent the first generalizable approach for mapping the guest distribution in heterogeneous host–guest catalytic systems, providing a foundation for predicting and tailoring the performance of catalysts integrated into various porous supports.

Thompson, William J.↗

DOE OSTI2025

Sequential Infiltration Synthesis of Cadmium Sulfide Discrete Atom Clusters

Abstract Exposure of soft material templates to alternating volatile chemical precursors can produce inorganic deposition within the permeable template (e.g. a polymer thin film) in a process akin to atomic layer deposition (ALD). While such sequential infiltration synthesis (SIS) processes have now been demonstrated for many metal oxides, we report an SIS process for a transition metal sulfide – CdS. Gas phase dimethyl cadmium and hydrogen sulfide precursors infiltrated into poly(4‐vinylpyridine) thin films result in the 3D‐nucleation of clusters consistent with a cubane‐type Cd 4 S 4 core that are variably terminated with methyl, thiol and hydroxy capping ligands. First principles models and simulation of few‐atom Cd‐based clusters are consistent with electronic and vibrational spectroscopy and grazing‐incidence total X‐ray scattering measurements of 3D‐cluster‐arrays synthesized at 80 °C. The direct synthesis of few‐atom transition metal sulfide clusters within polymer thin films will provide a versatile new route to precision architectures for light‐absorbing materials including solar energy harvesting and conversion applications.

Jayaweera, Nuwanthaka P. [Material Science Divisio↗

DOE OSTI2025

Fe‐Triazolate Metal–Organic Frameworks as Water Oxidation Catalysts with Dual Photoanode Functionality

Artificial photosynthesis is an emerging technology that achieves renewable fuels, such as hydrogen, from sunlight. Its realization depends on finding highly active and stable catalysts of water splitting and photoactive materials for light absorption. To be scalable, these should contain only abundant elements. Here, for the first time, Fe-triazolate (Fe(ta) 2 ) and its metal substituted derivatives (Fe-Metal(ta) 2 ) Metal-organic frameworks (MOFs) are characterized as new dual-function materials for photo-absorption and water oxidation catalysis in acidic media. The materials were studied by a range of structural, spectroscopic, and computational density functional theory (DFT) techniques. Fe(ta) 2 and Fe-Mn(ta) 2 were found to be highly active and stable in chemical and photochemical water oxidation, and in addition function as photoanodes, with photo-electrocatalytic currents (∼2.00 x 10 −3 Acm −2 at + 1.4 V vs. Ag/AgCl) at pH = 1. The possibility of a unique catalytic mechanism where O─O bond formation is possible from the coupling of two adjacent Fe IV = O fragments was demonstrated by DFT analysis. Thus, Fe-triazolate MOF has been established as a new, stable, scalable, versatile, and efficient platform for sustainable energy conversion in the realm of artificial photosynthesis.

Artificial photosynthesis↗

DOE OSTI2024

Electrochemical Imaging of Precisely‐Defined Redox and Reactive Interfaces

Abstract Understanding the diverse electrochemical reactions occurring at electrode‐electrolyte interfaces (EEIs) is a critical challenge to developing more efficient energy conversion and storage technologies. Establishing a predictive molecular‐level understanding of solid electrolyte interphases (SEIs) is challenging due to the presence of multiple intertwined chemical and electrochemical processes occurring at battery electrodes. Similarly, chemical conversions in reactive electrochemical systems are often influenced by the heterogeneous distribution of active sites, surface defects, and catalyst particle sizes. In this mini review, we highlight an emerging field of interfacial science that isolates the impact of specific chemical species by preparing precisely‐defined EEIs and visualizing the reactivity of their individual components using single‐entity characterization techniques. We highlight the broad applicability and versatility of these methods, along with current state‐of‐the‐art instrumentation and future opportunities for these approaches to address key scientific challenges related to batteries, chemical separations, and fuel cells. We establish that controlled preparation of well‐defined electrodes combined with single entity characterization will be crucial to filling key knowledge gaps and advancing the theories used to describe and predict chemical and physical processes occurring at EEIs and accelerating new materials discovery for energy applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

In Situ Alloying Enabled by Active Liquid Metal Filler for Self‐Healing Composite Polymer Electrolytes

Abstract Solid inorganics, known for kinetically inhibiting polymer crystallization and enhancing ionic conductivity, have attracted significant attention in solid polymer electrolytes. However, current composite polymer electrolytes (CPEs) are still facing challenges in Li metal batteries, falling short of inhibiting severe dendritic growth and resulting in very limited cycling life. This study introduces Ga 62.5 In 21.5 Sn 16 (Galinstan) liquid metal (LM) as an active liquid alternative to conventional passive solid fillers, aiming at realizing self‐healing protection against dendrite problems. Compared to solid inorganics, for example silica, LM droplets could more significantly reduce polymer crystallinity and enhance Li‐ion conductivity due to their liquid nature, especially at temperatures below the polymer melting point. More importantly, LMs are unraveled as dynamic chemical traps, which are capable of blocking and consuming lithium dendrites upon contact via in situ alloying during battery operation and further inhibiting dendritic growth due to the lower deposition energy barrier of the formed Li‐LM alloy. As a proof of concept, by strategically designing an asymmetric CPE with the active LM filling, a solid‐state Li/LiFePO 4 battery achieves promising full‐cell functionality with notable rate performance and stable cycle life. This active filler‐mediated self‐healing approach could bring new insights into the battery design in versatile solid‐state systems.

Wu, Kai↗

DOE OSTI2024

Synergistic Tuning of Microstructure and Morphology in Carbon Molecular Sieve Hollow Fibers for Propylene/Propane Separation

Liu, Zhongyun↗

DOE OSTI2024

Catalytically Active Site Mapping Realized through Energy Transfer Modeling

Thompson, William J.↗

DOE OSTI2025

Sequential Infiltration Synthesis of Cadmium Sulfide Discrete Atom Clusters

Exposure of soft material templates to alternating volatile chemical precursors can produce inorganic deposition within the permeable template (e.g. a polymer thin film) in a process akin to atomic layer deposition (ALD). While such sequential infiltration synthesis (SIS) processes have now been demonstrated for many metal oxides, we report an SIS process for a transition metal sulfide – CdS. Gas phase dimethyl cadmium and hydrogen sulfide precursors infiltrated into poly(4-vinylpyridine) thin films result in the 3D-nucleation of clusters consistent with a cubane-type Cd 4 S 4 core that are variably terminated with methyl, thiol and hydroxy capping ligands. First principles models and simulation of few-atom Cd-based clusters are consistent with electronic and vibrational spectroscopy and grazing-incidence total X-ray scattering measurements of 3D-cluster-arrays synthesized at 80 °C. The direct synthesis of few-atom transition metal sulfide clusters within polymer thin films will provide a versatile new route to precision architectures for light-absorbing materials including solar energy harvesting and conversion applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Radical Borylation of Alkyl Bromides by Photoinduced Halogen‐Atom Transfer

Alkyl organoboron compounds are versatile synthons in organic synthesis, enabling rapid access to a variety of carbon─carbon and carbon-heteroatom bonds. As such, strategies to efficiently access carbon-boron bonds from simple chemical feedstocks are highly desirable. The radical borylation of alkyl bromides presents an attractive approach. However, the activation of alkyl bromides typically requires strong reductants or transition-metal catalysts. Herein, we report a metal-free radical borylation strategy of various alkyl bromides utilizing a photoinduced silyl radical to mediate a halogen-atom transfer process. This method demonstrates broad utility and functional group tolerance among various primary, secondary, and tertiary unactivated alkyl bromides and can facilitate the functionalization of pharmaceutically relevant motifs. Mechanistic and computational studies support a radical-chain pathway involving a silyl radical-mediated halogen-atom transfer.

Alkyls↗

DOE OSTI2025

Extrusion‐Based Printing of Nanostructured Fatty Acid Gels Incorporated in Hydrogels

Soft materials with unique nanostructures such as lamellar, hexagonal, and cubic morphologies can replicate complex structures that have potential in various fields, including biomedical and industrial applications. However, a key challenge in advancing the broader applications of 3D printing for these nanostructured soft materials is insufficient mechanical properties that hinder their printability and compromise structural stability in the final product. In this study, the suitability of a fatty acid‐based lamellar gel is evaluated for direct extrusion‐based 3D printing. Here, the lamellar gel with varying water content is integrated with a photocurable hydrogel to preserve the shape and stability of the final prints. Complex 2D and 3D design patterns are used to assess extrusion behavior, structural stability, and print precision under varying pressures. Small‐angle X‐ray Scattering (SAXS) measurements reveal the formation of lamellar nanostructures and confirm their retention after photocuring in various gels. Rheological analysis confirms that these gels exhibit key properties suitable for extrusion‐based 3D printing, such as shear‐thinning behavior. Additionally, tensile testing is conducted to evaluate the mechanical properties across cured print samples. This study underscores the potential of nanostructured gels as a robust and versatile platform, facilitating the development of materials engineered for various applications.

36 MATERIALS SCIENCE↗

DOE OSTI2025

Reductant‐ or Light‐Driven ATP‐Independent Reduction of CO 2 by Nitrogenase MoFe Protein

Nitrogenase is a versatile metalloenzyme that activates and reduces small molecules like N 2 , CO, and CO 2 into value-added chemicals at ambient conditions. Previously, it is shown that the Mo-nitrogenase could reduce CO 2 to CO, but not to hydrocarbons, in an ATP-dependent reaction. Here, it is reported that the ability of the catalytic component of Mo-nitrogenase (MoFe protein) enables ATP-independent reduction of CO 2 to up to C 4 hydrocarbons in room-temperature reactions driven by a chemical reductant (Eu II –DTPA) or visible light (via CdS@ZnS (CZS) quantum dots). Moreover, an opposite deuterium isotope effect is observed on the Eu II –DTPA driven reactions of CO 2 reduction by MoFe protein and its V-counterpart (VFe protein), in that the former displays higher activities in H 2 O, and the latter displays higher activities in D 2 O. Furthermore, these results provide an important foundation for further mechanistic exploration of the nitrogenase-enabled, atypical Fischer–Tropsch type reaction that uses CO 2 instead of CO as a substrate; moreover, they serves as a potential template for the future development of nitrogenase-based applications that effectively recycle the greenhouse gas CO 2 into valuable fuel products.

C-C coupling↗

DOE OSTI2024

Models for Single–Site Heterogeneous Catalysts on Carbon: MoO 2 Epoxidation Catalyst Anchored to a Fullerene

Single-site molybdenum dioxo catalysts, fullerenol/MoO 2 , are prepared via grafting precursor (DME)MoO 2 Cl 2 onto a highly polyhydroxylated fullerene (ful) and an isomerically-pure and well-defined fullerene (ful*). These catalyst structures are characterized by ICP-OES, XPS, XANES, EXAFS, DRIFT, Raman, and NMR spectroscopy, and DFT. Mo 3d 5/2 XPS and Mo K-edge XANES assign the oxidation state as Mo(VI). Mo EXAFS data fitting reveals two Mo=O double and two Mo–O single bonds at distances of 1.7 and 1.9 Å, respectively, while an Mo=O stretchingl mode is observed at ~950 cm –1 by DRIFT and Raman spectroscopy. These data align well with DFT computational results, supporting the proposed catalyst structure as Fullerene(-μ-O-) 2 M(=O) 2 . Additionally, DFT provides insight into the energetically favorable grafting sites for an isomerically pure fullerenol. The scope of fullerenol/MoO 2 mediated alkene epoxidation includes abiotic alkenes, natural occurring terpenes, and conjugated olefins. For cyclooctene the rate law is first-order in [Mo], near first order in [olefin] and zero-order in [t-butyl hydroperoxide]. A plausible reaction mechanism involves peroxide addition first and then cyclooctene addition directly across the peroxo bond forming the epoxide product, consistent with DFT computation. Overall, fullerenol/MoO 2 shows promise as a sustainable and structurally well-defined system with versatile catalytic activity and good epoxidation recyclability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

A One‐Pot Biocatalytic Cascade to Access Diverse l ‐Phenylalanine Derivatives from Aldehydes or Carboxylic Acids

Abstract Nonstandard amino acids (nsAAs) that are l ‐phenylalanine derivatives with aryl ring functionalization have long been harnessed in natural product synthesis, therapeutic peptide synthesis, and diverse applications of genetic code expansion. Yet, to date, these chiral molecules have often been the products of poorly enantioselective and environmentally harsh organic synthesis routes. Here, we reveal the broad specificity of multiple natural pyridoxal 5′‐phosphate (PLP)‐dependent enzymes, specifically an l ‐threonine transaldolase, a phenylserine dehydratase, and an aminotransferase, toward substrates that contain aryl side chains with diverse substitutions. We exploit this tolerance to construct a one‐pot biocatalytic cascade that achieves high‐yield synthesis of 18 diverse l ‐phenylalanine derivatives from aldehydes under mild aqueous reaction conditions. We demonstrate the addition of a carboxylic acid reductase module to this cascade to enable the biosynthesis of l ‐phenylalanine derivatives from carboxylic acids that may be less expensive or less reactive than the corresponding aldehydes. Finally, we investigate the scalability of the cascade by developing a lysate‐based route for preparative‐scale synthesis of 4‐formyl‐ l ‐phenylalanine, a nsAA with a bio‐orthogonal handle that is not readily market‐accessible. Overall, this work offers an efficient, versatile, and scalable route with the potential to lower manufacturing costs and democratize synthesis for many valuable nsAAs.

Anderson, Shelby R. [Department of Chemical and Bi↗

DOE OSTI2025

Divergent Responses of Carbon Nitride Dot‐Based Amorphous Species and Small Molecule Hybrids to Trace Level Analytes

Bottom-up synthesis of carbon nitride dots (CNDs) offers a versatile platform for the creation of diverse nanomaterials with tunable properties. Here, we report a facile hydrothermal approach using citric acid (CA) and urea (U) as precursors to synthesize CNDs with varying degrees of condensation and crystallinity. By carefully controlling reaction conditions and post-synthetic treatments, we obtained two distinct fractions: a polycrystalline fraction composed of small-molecule hybrids and an amorphous fraction containing CNDs. We then sought to understand how the dominant species in these fractions impact sensing abilities using trace-level explosive exemplars. In conclusion, the results have important implications for sensing and related applications where understanding the complex interplay between synthetic conditions and post-synthetic processing play vital roles in determining the final properties of CND materials.

carbon nitride dots↗

DOE OSTI2025

X‐Ray Absorption Studies of Local Structure of Dilute Ionic Species in Molten Salts

Molten salts are crucial materials with exceptional properties that make them suitable for applications such as heat transfer media, coolants, and liquid fuels in molten salt nuclear reactors and the concentrated solar power industry. Understanding their properties requires unraveling the intricate mysteries of their structure. To achieve this, advanced characterization tools are essential. Among various techniques, X‐ray absorption fine structure (XAFS) stands out as a versatile method capable of studying the structure of molten salts under in situ conditions. This review highlights recent advancements in the application of XAFS for investigating the local structure of molten salts, discusses its limitations and potential improvements, and explores complementary approaches such as simulations, machine learning, and correlative experimental methods.

22 - GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2025

Selective Recovery of Critical Minerals from Simulated Electronic Wastes Via Reaction‐Diffusion Coupling

Abstract Atom‐ and energy‐efficient chemical separations are urgently needed to meet the surging demand for critical materials that has strained supply chains and threatened environmental damage. In this study, we used reaction‐diffusion coupling to separate iron, neodymium, and dysprosium ions from model feedstocks of permanent magnets, which are typically found in electronic wastes. Feedstock solutions were placed in contact with a hydrogel loaded with potassium hydroxide and/or dibutyl phosphate, resulting in complex precipitation patterns as the various metal ions diffused into the reaction medium. Specifically, we observed the precipitation of up to 40 mM of iron from the feedstock, followed by the enrichment of 73 % dysprosium, and the extraction of >95 % neodymium product at a further distance from the solution‐gel interface. We designed a series of experiments and simulations to determine the relevant ion diffusivities, D Nd =5.4×10 −10 and D Dy =5.1×10 −10 m 2 /s, and precipitation rates, k Nd =1.0×10 −5 and k Dy =5.0×10 −3 m 9 mol −3 s −1 , which enabled a numerical model to be established for predicting the distribution of products in the reaction medium. Our proof‐of‐concept study validates reaction‐diffusion coupling as an effective and versatile approach for critical materials separations, without relying on ligands, membranes, resins, or other specialty chemicals.

Wang, Qingpu [Physical and Computational Sciences ↗

DOE OSTI2025

Biotransformation of Phenolics in Spent Liquor from Aqueous Ammonia Pretreatment

Spent liquors of biomass pretreatment provide a source for renewable chemical production. These liquors require treatment before being discharged; otherwise, they negatively impact the environment. Herein, spent liquors from aqueous ammonia pretreatment of poplar wood are characterized for phenolic content via liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The main phenolics are phenol, p-hydroxybenzamide (pHBAm), and p-hydroxybenzoic acid (pHBA), of which pHBAm and pHBA are produced from the ester-linked p-hydroxybenzoates in poplar wood. Phenol is produced from pHBA via decarboxylation. The potential biotransformation of the extracted phenolics into 2-pyrone-4,6-dicarboxylic acid (PDC) is assessed using an engineered strain of Novosphingobium aromaticivorans DSM12444 (PDC strain). Biotransformation of pHBAm to PDC is shown to be possible in the presence of pHBA, but not when pHBAm is the sole phenolic substrate, this is the first reported observation of N. aromaticivorans producing PDC from an aromatic amide. The phenol present is not transformed to PDC and does not inhibit PDC production. This study demonstrates that the phenolic amide in spent liquor from ammonia pretreatment can be valorized via biotransformation using N. aromaticivorans, which adds to the growing versatility of N. aromaticivorans as a microbial chassis for converting plant-derived compounds to useful products.

biomass↗