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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Is a Malleable Active Site Loop the Key to High Substrate Promiscuity? Hybrid, Biocatalytic Route to Structurally Diverse Taxoid Side Chains with Remarkable Dual Stereocontrol

Abstract These studies reveal the first structure ofClostridium acetobutylicumalcohol dehydrogenase (CaADH), a protein exhibiting remarkable substrate promiscuity and stereochemical fidelity. The CaADH enzyme is utilized here for synthesizing 20 potential aryl isoserine side chains for the Taxotere family of tubulin‐binding chemotherapeutics. The approach involves dynamic reductive kinetic resolution (DYRKR) upon the corresponding α‐chloro‐β‐keto esters, showing high D‐synstereoselectivity, including those leading to the clinically relevant milataxel (Ar = 2‐furyl) and simotaxel (Ar = 2‐thienyl) side chains. Furthermore, various cross‐coupling chemistries performed on thep‐bromophenyl isoserine side chain significantly enhance the structural diversity of the taxoid side chain library obtained (16 additional taxoid side chains). The CaADH structure is notable: (i) the nicotinamide cofactor is bound in ananti‐conformation, with the amide carbonyl occupying the ketone binding pocket, and (ii) a flexible loop near the active site likely contributes to the remarkable substrate promiscuity observed in CaADH. We present our perspective on the dynamic nature of the CaADH active site through molecular dynamics simulation, proposing a halogen bonding model as a potential mechanism for the remarkable selectivity for an (S)‐configured C─Cl bond, in addition to the D‐facial selectivity, demonstrated across 20 diverse substrates by this remarkable short‐chain dehydrogenase enzyme.

Chemistry↗
DOE OSTI2025

Upcycling of Waste Plastics into Carboxylic Acids for Biodegradable Surfactants

This work outlines a process for producing high‐purity (>95%) carboxylate surfactants from post‐consumer recycled high‐density polyethylene (PCR‐HDPE). The approach involves the thermal depolymerization of PCR‐HDPE via pyrolysis, followed by fractional distillation to isolate C9–C14 olefins. These olefins undergo hydroformylation using cobalt carbonyl catalysts to generate aldehydes, which are subsequently oxidized to carboxylic acids using Pinnick oxidation under mild aqueous‐phase conditions. Neutralization of the resulting carboxylic acids with sodium hydroxide produces plastic‐derived carboxylate surfactants (PDCs) in the form of sodium carboxylates. Subsequent purification steps ensure surfactant‐grade purity and enable accurate assessment of physicochemical properties. The resulting PDCs are evaluated for critical micelle concentration (CMC), foamability, surface tension reduction, and calcium ion tolerance, demonstrating competitive behavior with conventional anionic carboxylate surfactants. This route provides a sustainable alternative for surfactant production, reducing reliance on fossil‐derived feedstocks and valorizing plastic waste streams through chemical upcycling.

Biodegradable surfactants↗
DOE OSTI2023

Three-dimensional Polymers as Organic Cathodes for Affordable and Sustainable Sodium/Potassium-ion Batteries

Redox-active polymers (RAPs) are promising organic electrode materials for affordable and sustainable batteries due to their flexible chemical structures and negligible solubility in the electrolyte. Developing high-dimensional RAPs with porous structures and crosslinkers can further improve their stability and redox capability by reducing the solubility and enhancing reaction kinetics. Further, this work reports two three-dimensional (3D) RAPs as stable organic cathodes in Na-ion batteries (NIBs) and K-ion batteries (KIBs). Carbonyl functional groups are incorporated into the repeating units of the RAPs by the polycondensation of Tetrakis(4-aminophenyl)methane and two different dianhydrides. The RAPs with interconnected 3D extended conjugation structures undergo multi-electron redox reactions and exhibit high performance in both NIBs and KIBs in terms of long cycle life (up to 8000 cycles) and fast charging capability (up to 2 A g -1 ). The results demonstrate that developing 3D RAPs is an effective strategy to achieve high-performance, affordable, and sustainable NIBs and KIBs.

25 ENERGY STORAGE↗
DOE OSTI2016

High‐Pressure‐Induced Pseudo‐oxidation of Copper Surfaces by Carbon Monoxide

Abstract Instantaneous electronic and structural modifications of Cu surfaces by high‐pressure CO were explored. At pressures over a millibar range the coverage of CO on the Cu(1 1 1) surface reached approximately one monolayer, and we observed several shake‐up peaks in the Cu 2p photoemission spectra for the first time by using ambient pressure X‐ray photoelectron spectroscopy. These shake‐up peaks resembled those obtained for oxidized surface Cu atoms. We propose that these changes are related to the generation of a copper–carbonyl complex and subsequent Cu surface restructuring owing to lateral CO–CO repulsions. The generality of this finding was investigated in two model reactions, the water‐gas shift and CO oxidation, on a Cu(1 1 1) surface, and we clearly identified the pseudo‐oxidation of Cu. These reversible changes were found to be independent of the orientation of the Cu surface and are of general importance for Cu‐based heterogeneous catalysis.

Zhang, Xueqiang↗
DOE OSTI2018

Copper-Cobalt-Cerium Ternary Oxide as an Additive to a Conventional Platinum-Group-Metal Catalyst for Automotive Exhaust Catalysis

Recently, we reported on a ternary mixed-oxide catalyst that showed low-temperature CO oxidation activity under lean exhaust conditions without inhibition by hydrocarbons such as propene. However, the hydrocarbon oxidation activity of this Cu–Co–Ce (CCC) catalyst cannot be considered as a stand-alone solution to low-temperature automotive exhaust catalysis. To achieve both low-temperature oxidation of pollutants and a reduction in the total platinum-group-metal (PGM) content, we examined a 50 % physical mixture of traditional Pt/Al 2 O 3 and our CCC catalyst in two simulated exhaust protocols. Using this physical mixture, we were able to obtain equivalent or better hydrocarbon activity than the baseline Pt/Al 2 O 3 catalyst with half the total PGM content as well as increased sulfur tolerance for the CCC component of the mixture. Diffuse reflectance infrared Fourier transform spectroscopy data confirmed that despite exposure of sulfur-sensitive CCC to SO 2 , Cu + -carbonyl binding sites could still be seen if the catalyst was mixed with Pt/Al 2 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

α‐Fluoroalcohols: Synthesis and Characterization of Perfluorinated Methanol, Ethanol and n ‐Propanol, and their Oxonium Salts

Abstract The thermally unstable, primary perfluoroalcohols, CF 3 OH, C 2 F 5 OH, and n C 3 F 7 OH, were conveniently prepared from the corresponding carbonyl compounds in anhydrous HF solution. Experimental values for the reaction enthalpies and entropies were derived from the temperature dependence of the R f COF+HF⇄R f CF 2 OH ( R f =F, CF 3 , CF 3 CF 2 ) equilibria by NMR spectroscopy. Electronic structure calculations of the gas‐phase and solution reaction energies, gas‐phase acidities and heats of formation were carried out at the G3MP2 level, showing that these compounds are strong acids. Protonation of these alcohols in HF/SbF 5 produced the perfluoroalkyl oxonium salts R f CF 2 OH 2 + SbF 6 − .

Baxter, Amanda F.↗
DOE OSTI2020

Realization of an Asymmetric Non‐Aqueous Redox Flow Battery through Molecular Design to Minimize Active Species Crossover and Decomposition

Abstract This communication presents a mechanism‐based approach to identify organic electrolytes for non‐aqueous redox flow batteries (RFBs). Symmetrical flow cell cycling of a pyridinium anolyte and a cyclopropenium catholyte resulted in extensive capacity fade due to competing decomposition of the pyridinium species. Characterization of this decomposition pathway enabled the rational design of next‐generation anolyte/catholyte pairs with dramatically enhanced cycling performance. Three factors were identified as critical for slowing capacity fade: (1) separating the anolyte–catholyte in an asymmetric flow cell using an anion exchange membrane (AEM); (2) moving from monomeric to oligomeric electrolytes to limit crossover through the AEM; and (3) removing the basic carbonyl moiety from the anolyte to slow the protonation‐induced decomposition pathway. Ultimately, these modifications led to a novel anolyte–catholyte pair that can be cycled in an AEM‐separated asymmetric RFB for 96 h with >95 % capacity retention at an open circuit voltage of 1.57 V.

Shrestha, Anuska↗
DOE OSTI2022

E ‐selective Semi‐hydrogenation of Alkynes under Mild Conditions by a Diruthenium Hydride Complex

Abstract The synthesis, characterization and catalytic activity of a new class of diruthenium hydrido carbonyl complexes bound to the t Bu PNNP expanded pincer ligand is described. Reacting t Bu PNNP with two equiv of RuHCl(PPh 3 ) 3 (CO) at 140 °C produces an insoluble air‐stable complex, which was structurally characterized as [Ru 2 ( t Bu PNNP)H(μ‐H)Cl(μ‐Cl)(CO) 2 ] ( 1 ) using solid‐state NMR, IR and X‐ray absorption spectroscopies and follow‐up reactivity. A reaction with KO t Bu results in deprotonation of a methylene linker to produce [Ru 2 ( t Bu PNNP * )H(μ‐H)(μ‐O t Bu)(CO) 2 ] ( 3 ) featuring a partially dearomatized naphthyridine core. This enables metal‐ligand cooperative activation of H 2 analogous to the mononuclear analogue, [Ru( t Bu PNP*)H(CO)]. In contrast to the mononuclear system, the bimetallic analogue 3 catalyzes the E ‐selective semi‐hydrogenation of alkynes at ambient temperature and atmospheric H 2 pressure with good functional group tolerance. Monitoring the semi‐hydrogenation of diphenylacetylene by 1 H NMR spectroscopy shows the intermediacy of Z ‐stilbene, which is subsequently isomerized to the E ‐isomer. Initial findings into the mode of action of this system are provided, including the spectroscopic characterization of a polyhydride intermediate and the isolation of a deactivated species with a partially hydrogenated naphthyridine backbone.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Design of gem -Difluoro- bis -Tetrahydrofuran as P2 Ligand for HIV-1 Protease Inhibitors to Improve Brain Penetration: Synthesis, X-ray Studies, and Biological Evaluation

The structure–based design, synthesis, biological evaluation, and X–ray structural studies of fluorine–containing HIV–1 protease inhibitors are described. The synthesis of both enantiomers of the gem–difluoro–bis–THF ligands was carried out in a stereoselective manner using a Reformatskii–Claisen reaction as the key step. Optically active ligands were converted into protease inhibitors. Two of these inhibitors, (3R,3aS,6aS)–4,4–difluorohexahydrofuro[2,3–b]furan–3–yl(2S,3R)–3–hydroxy–4–((N–isobutyl–4–methoxyphenyl)sulfonamido)–1–phenylbutan–2–yl) carbamate (3) and (3R,3aS,6aS)–4,4–difluorohexahydrofuro[2,3–b]furan–3–yl(2S,3R)–3–hydroxy–4–((N–isobutyl–4–aminophenyl)sulfonamido)phenylbutan–2–yl) carbamate (4), exhibited HIV–1 protease inhibitory K i values in the picomolar range. Both 3 and 4 showed very potent antiviral activity, with respective EC 50 values of 0.8 and 3.1 nM against the laboratory strain HIV–1 LAI . The two inhibitors exhibited better lipophilicity profiles than darunavir, and also showed much improved blood–brain barrier permeability in an in vitro model. A high–resolution X–ray structure of inhibitor 4 in complex with HIV–1 protease was determined, revealing that the fluorinated ligand makes extensive interactions with the S2 subsite of HIV–1 protease, including hydrogen bonding interactions with the protease backbone atoms. Moreover, both fluorine atoms on the bis–THF ligand formed strong interactions with the flap Gly 48 carbonyl oxygen atom.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Understanding the Reactive Adsorption of H 2 S and CO 2 in Sodium-Exchanged Zeolites

Purifying sour natural gas streams containing hydrogen sulfide and carbon dioxide has been a long-standing environmental and economic challenge. In the presence of cation-exchanged zeolites, these two acid gases can react to form carbonyl sulfide and water (H 2 S+CO 2 H 2 O+COS), but this reaction is rarely accounted for. In this work, we carry out reactive first-principles Monte Carlo (RxFPMC) simulations for mixtures of H 2 S and CO 2 in all-silica and Na-exchanged forms of zeolite beta to understand the governing principles driving the enhanced conversion. The RxFPMC simulations show that the presence of Na + cations can change the equilibrium constant by several orders of magnitude compared to the gas phase or in all-silica beta. The shift in the reaction equilibrium is caused by very strong interactions of H 2 O with Na + that reduce the reaction enthalpy by about 20 kJmol -1 . The simulations also demonstrate that the siting of Al atoms in the framework plays an important role. Lastly, the RxFPMC method presented here is applicable to any chemical conversion in any confined environment, where strong interactions of guest molecules with the host framework and high activation energies limit the use of other computational approaches to study reaction equilibria.

03 NATURAL GAS↗
DOE OSTI2024

17 O NMR Spectroscopy Reveals CO 2 Speciation and Dynamics in Hydroxide-Based Carbon Capture Materials

Carbon dioxide capture technologies are set to play a vital role in mitigating the current climate crisis. Solid-state 17 O NMR spectroscopy can provide key mechanistic insights that are crucial to effective sorbent development. In this work, we present the fundamental aspects and complexities for the study of hydroxide-based CO 2 capture systems by 17 O NMR. We perform static density functional theory (DFT) NMR calculations to assign peaks for general hydroxide CO 2 capture products, finding that 17 O NMR can readily distinguish bicarbonate, carbonate and water species. However, in application to CO 2 binding in two test case hydroxide-functionalised metal-organic frameworks (MOFs) – MFU-4l and KHCO 3 -cyclodextrin-MOF, we find that a dynamic treatment is necessary to obtain agreement between computational and experimental spectra. We therefore introduce a workflow that leverages machine-learning force fields to capture dynamics across multiple chemical exchange regimes, providing a significant improvement on static DFT predictions. In MFU-4l, we parameterise a two-component dynamic motion of the bicarbonate motif involving a rapid carbonyl seesaw motion and intermediate hydroxyl proton hopping. For KHCO 3 -CD-MOF, we combined experimental and modelling approaches to propose a new mixed carbonate-bicarbonate binding mechanism and thus, we open new avenues for the study and modelling of hydroxide-based CO 2 capture materials by 17 O NMR.

NMR spectroscopy↗
DOE OSTI2025

Unraveling Electronic Effects that Influence the Bimolecular Chemistry of Fluorinated Criegee Intermediates

Ozonolysis is important for the removal of unsaturated volatile organic compounds emitted into the Earth's atmosphere. The alkene + ozone reaction (alkene ozonolysis) forms a carbonyl oxide – a Criegee intermediate (CI). CIs are interesting from an atmospheric chemistry perspective. They are implicated in enhancing the oxidizing capacity of the troposphere and in secondary organic aerosol formation. CIs may participate in bimolecular reactions with trace atmospheric vapors like water and methanol. Here, the chemistry of the two isomers of CFHOO and of CF 3 CHOO with water, water dimer, and methanol is explored. The present study confirms that the syn-conformer is the minimum energy structure for both CIs and that the reactions of anti-CFHOO display slightly lower activation energies cf. syn-CFHOO, thus promoting faster reaction. For both syn- and anti-CFHOO, the energy barrier in the pathway to adding water, water dimer, or methanol is lower—and the overall reaction exoergicity greater—than for the corresponding reactions involving the nonfluorinated analogue, CH 2 OO. Here, the corresponding bimolecular reaction rates are thus predicted to be faster for CFHOO than CH 2 OO. Similar reactivity trends are found when comparing the same reactions of syn-CF 3 CHOO, cf. syn-CH 3 CHOO, but not when comparing the energetics of the reactions involving anti-CF 3 CHOO cf. anti-CH 3 CHOO.

Guidry, Lily M. [University of Louisiana at Lafaye↗
DOE OSTI2019

Competition between Singlet Fission and Spin‐Orbit‐Induced Intersystem Crossing in Anthanthrene and Anthanthrone Derivatives

Abstract Singlet and triplet excited‐state dynamics of anthanthrene and anthanthrone derivatives in solution are studied. Triisopropylsilyl‐ (TIPS) or H‐terminated ethynyl groups are used to tune the singlet and triplet energies to enable their potential applications in singlet fission and triplet fusion processes. Time‐resolved optical and electron paramagnetic resonance (EPR) spectroscopies are used to obtain a mechanistic understanding of triplet formation. The anthanthrene derivatives form triplet states efficiently at a rate (ca. 10 7 s −1 ) comparable to radiative singlet fluorescence processes with approximately 30 % triplet yields, despite their large S 1 ‐T 1 energy gap (>1 eV) and the lack of carbonyl groups. In contrast, anthanthrone has a higher triplet yield (50±10 %) with a faster intersystem crossing rate (2.7 10 8 s −1 ) because of the n‐π* character of the S 1 ←S 0 transition. Analysis of time‐resolved spin‐polarized EPR spectra of these compounds reveals that the triplet states are primarily generated by the spin‐orbit‐induced intersystem crossing mechanism. However, at high concentrations, the EPR spectrum of the 4,6,10,14‐tetrakis(TIPS‐ethynyl)anthanthrene triplet state shows a significant contribution from a non‐Boltzmann population of the m s =0 spin sublevel, which is characteristic of triplet formation by singlet fission.

Jue Bae, Youn↗
DOE OSTI2019

Catalytic One‐Pot Conversion of Renewable Platform Chemicals to Hydrocarbon and Ether Biofuels through Tandem Hf(OTf) 4 +Pd/C Catalysis

Abstract Efficient conversion of renewable biomass platform chemicals into high‐quality fuels remains challenging. A one‐pot catalytic approach has been developed to synthesize various structurally defined biofuels by using Hf(OTf) 4 and Pd/C for selective tandem catalysis and 2‐methylfuran (2‐MF) as a renewable feedstock. 2‐MF first undergoes Lewis acid‐catalyzed hydroxyalkylation/alkylation (HAA) condensation with carbonyl compounds to afford intermediates containing the targeted carbon skeletons of hydrocarbon or ether products, and these intermediates then undergo hydrogenation or hydrodeoxygenation to afford the target products, catalyzed by metal triflate+Pd/C in the same pot. The present process can produce structurally defined alkanes and cyclic ethers under mild conditions.

Liu, Dong‐Huang↗
DOE OSTI2024

A New Triketone Ligand for Extraction of Lithium from Brines**

Recovery of lithium from brines by liquid-liquid solvent extraction (LLE) with diketones and synergistic co-ligands has been investigated for decades, but industrial application has been limited. In pursuit of a ligand with improved properties, a series of ketonamides with beta-carbonyl groups were designed, synthesized, and tested in extraction of lithium from sulfate and carbonate simulants of clay mineral tailing leachates. The best performing ligand, a novel tricarbonyl amide, was characterized for lithium extraction with and without four synergistic co-ligands. Further, the tricarbonyl amide combined with the synergistic co-ligand Cyanex-923 was absorbed on a resin support. The ligand-modified resin was tested for performance in extraction of dilute brine simulants and up to 60 % recovery of lithium was achieved.

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

Lipids status and copper in a single astrocyte of the rat model for amyotrophic lateral sclerosis: Correlative synchrotron-based X-ray and infrared imaging

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, causing death of motor neurons controlling voluntary muscles. The pathological mechanisms of the disease are only partially understood. The hSOD1-G93A ALS rat model is characterized by an overexpression of human mutated SOD1, causing increased vulnerability by forming intracellular protein aggregates, inducing excitotoxicity, affecting oxidative balance and disturbing axonal transport. In this study we followed the bio-macromolecular organic composition and compartmentalization together with trace metal distribution in situ in single astrocytes from the ALS rat model and compared them to the control astrocytes from nontransgenic littermates by simultaneous use of two synchrotron radiation-based methods: Fourier transform infrared microspectroscopy (SRFTIR) and hard X-ray fluorescence microscopy (XRF). Here we show that ALS cells contained more Cu, which colocalized with total lipids, increased carbonyl groups and oxidized lipids, thus implying direct involvement of Cu in oxidative stress of lipidic components without direct connection to protein aggregation in situ.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Synthesis of Stable Isotope Labeled Chloroquine, Amodiaquine and Their Metabolites

Anti–malaria drugs chloroquine, amodiaquine and their metabolites were stable isotope labeled with 13 C and 15N starting from uniformly 13 C labeled benzene and 15 N labeled potassium nitrate to give M+7 isotopomers. Here, chloroquine, and its metabolites were prepared from 7–chloro–1,2,3,4–tetrahydroquinolin–4–one through addition to the carbonyl with the corresponding amines; and the amodiaquine and its metabolites were prepared from 4,7–dichloroquinoline in a selective aryl–halogen exchange with the corresponding amines.

07 ISOTOPE AND RADIATION SOURCES↗