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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Direct Uranium Isotopic Analysis of Swipe Surfaces by Microextraction-ICP-MS

The ability to directly measure uranium isotope ratios on environmental swipes has been achieved through a solution-based microextraction process and represents a significant advancement toward the development of a rapid method to analyze international nuclear safeguard samples. Here, a microextraction probe is lowered and sealed onto the swipe surface, and analytes within the sampling site (~8 mm2) are dissolved and extracted into a flowing solvent of 2% nitric acid (HNO 3 ). The mobilized species are subsequently directed into an inductively coupled plasma-mass spectrometer (ICP-MS) for accurate and precise isotope ratio determination. This work highlights the novelty of the sampling mechanism, particularly with the direct coupling of the microextraction probe to the ICP-MS and measurement of uranium isotope ratios. The preliminary method detection limit for the microextraction-ICP-MS method, utilizing a quadrupole-based MS, was determined to be ~50 pg of 238 U. Additionally, precise and accurate isotope ratio measurements were achieved on uranium reference materials for both the major ( 235 U/ 238 U) and minor ( 234 U/ 238 U and 236 U/ 238 U) ratios. While the present work is focused on directly measuring uranium isotopic systems on swipe surfaces for nuclear safeguards and verification applications, the benefits would extend across many applications in which direct solid sampling is sought for elemental and isotopic analysis.

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

Comparing Sensor Fusion and Multimodal Chemometric Models for Monitoring U(VI) in Complex Environments Representative of Irradiated Nuclear Fuel

Optical sensors and chemometric models were leveraged for the quantification of uranium(VI) (0–100 μg mL –1 ), europium (0–150 μg mL –1 ), samarium (0–250 μg mL –1 ), praseodymium (0–350 μg mL –1 ), neodymium (0–1000 μg mL –1 ), and HNO 3 (2–4 M) with varying corrosion product (iron, nickel, and chromium) levels using laser fluorescence, Raman scattering, and ultraviolet–visible–near-infrared absorption spectra. In this paper, an efficient approach to developing and evaluating tens of thousands of partial least-squares regression (PLSR) models, built from fused optical spectra or multimodal acquisitions, is discussed. Each PLSR model was optimized with unique preprocessing combinations, and features were selected using genetic algorithm filters. The 7-factor D-optimal design training set contained just 55 samples to minimize the number of samples. The performance of PLSR models was evaluated by using an automated latent variable selection script. PLS1 regression models tailored to each species outperformed a global PLS2 model. PLS1 models built using fused spectra data and a multimodal (i.e., analyzed separately) approach yielded similar information, resulting in percent root-mean-square error of prediction values of 0.9–5.7% for the seven factors. Further, the optical techniques and data processing strategies established in this study allow for the direct analysis of numerous species without measuring luminescence lifetimes or relying on a standard addition approach, making it optimal for near-real-time, in situ measurements. Nuclear reactor modeling helped bound training set conditions and identified elemental ratios of lanthanide fission products to characterize the burnup of irradiated nuclear fuel. Leveraging fluorescence, spectrophotometry, experimental design, and chemometrics can enable the remote quantification and characterization of complex systems with numerous species, monitor system performance, help identify the source of materials, and enable rapid high-throughput experiments in a variety of industrial processes and fundamental studies.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Lessons Learned—Fluoride Exposure and Response

Laboratory research can expose workers to a wide variety of chemical hazards. Researchers must not only take personal responsibility for their safety but also inevitably rely on coworkers to also work safely. The foundations for protocols, requirements, and behaviors come from our history and lessons learned from others. For that reason, here, a recent incident is examined in which a researcher suffered hydrofluoric acid (HF) burns while working with an inorganic digestion mixture of aqueous HF (8%) and nitric acid (HNO 3 , 58%). HF education is critical for workers because delays in treatment, improper treatment, and delay of symptoms are all factors in unfavorable outcomes in case reports. Furthermore, while the potential severity of the incident was elevated due to bypassed engineered controls and lack of proper personal protective equipment, only minor injuries were sustained. We discuss the results of a causal analysis of the incident that revealed areas of improvement in protocols, personal protective equipment, and emergency response that could help prevent similar accidents from occurring. We also present simple improvements that anyone can implement to reduce the potential consequences of an accident, based upon our lessons learned.

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

Oxidative Self-Assembly of Au/Ag/Pt Alloy Nanoparticles into High-Surface Area, Mesoporous, and Conductive Aerogels for Methanol Electro-oxidation

The ability to assemble nanoparticles (NPs) into functional nanostructures is critical for the advancement of nanoscience. However, common assembling techniques utilize organic ligands or biomolecules, which are detrimental for charge transport and interparticle coupling, which impede the efficient integration of low-dimensional properties. Herein, we report a methodology for the self-supported assembly of ultra-small (3-6 nm) Au/Ag/Pt alloy NPs into large, free-standing alloy superstructures (aerogels) that exhibit direct NP connectivity, high surface area (125 ± 0.43 to142 ± 0.93 m 2 /g) and mesoporosity (21.6 ± 2.2 nm), and superior electrocatalytic activity for methanol oxidation reaction (MOR). Precursor Au/Ag/Pt alloy NPs and hydrogels were synthesized via stepwise galvanic replacement reaction (GRR) of the glutathione (GSH)-coated Ag NPs, followed by oxidative removal of the surfactant ligands. The composition of alloy aerogels was tuned by varying the oxidant/GSH molar ratio, which governs the extent of Ag dealloying with in-situ generated HNO 3 and increases the exposure of Au and Pt on the aerogel surface. The alloy aerogels exhibit superior MOR mass activity, which is 21.4 and 2.5 times higher than those of the precursor NPs and commercial Pt (40 wt.%)/C electrocatalysts, respectively. The MOR surface-specific activity (MOR-SSA) of the aerogels was improved by >17% when the Pt content was increased from 22.4% to 31.2%. The aerogels exhibit improved electronic conductivity, enhanced tolerance for carbonaceous byproducts, and maintained ~94% of the initial MOR activity at -0.3 V for 24 h in an alkaline medium. In conclusion, the interconnected porous superstructure of the aerogel provides a facile conduit for molecules to reach the pristine active surface whereas the presence of oxophilic Au promotes the dissociative adsorption of methanol, enabling the Au/Ag/Pt alloy aerogel a high efficiency, durable electrocatalyst for next generation of energy conversion studies.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Recovery of Oxidized Actinides, Np(VI), Pu(VI), and Am(VI), from Cocrystallized Uranyl Nitrate Hexahydrate: A Single Technology Approach to Used Nuclear Fuel Recycling

In this work, the utility of recovering cocrystallized Np, Pu, and Am from a uranyl nitrate hexahydrate crystalline phase has been examined. Progressive dissolution studies were carried out on samples of either Np(VI), Pu(VI), or Am(VI) cocrystallized with uranyl nitrate hexahydrate, resulting in a linear relationship between the amount of actinides dissolved as a function of volume of HNO 3 added, which indicates homogeneous distribution of the transuranic species throughout the crystalline solid. The ratio of the concentration of U to the heavier actinides was maintained over the entire dissolution and mimicked that of the starting cocrystallization solution. A series of five crystallization–dissolution–recrystallization cycles of uranyl nitrate hexahydrate from nitric acid have been achieved in the presence of Am(VI), where the behavior of Am(VI) followed that of U(VI) for each step of all five cycles. Negligible reduction of Am(VI) to Am(III) was observed between each recrystallization cycle. These results indicate the utility of a group hexavalent actinide cocrystallization approach toward used nuclear fuel recycling.

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

Synthesis of an Isostructural Series of 12-Coordinate Lanthanide Nitrate Hybrid Double Perovskites with Cubic Symmetry

In efforts to study the periodic chemical properties of the rare earth elements and their structural chemistry, a hybrid double perovskite phase A 2 B'BX 6 with the formula ((CH 3 ) 4 N) 2 KLn(NO 3 ) 6 (Ln = La–Lu, Y ex. Pm) was synthesized that crystallizes in the cubic space group, $Fm$$\bar{3}$$m$. This series was obtained via evaporative crystallization from a mixture of Ln(NO 3 ) 3 , KNO 3 , and (CH 3 ) 4 N·NO 3 in a 1:1:2 ratio from either H 2 O or 4.0 M HNO 3 . In this double perovskite structure, the B site containing the lanthanide ion is coordinated by six bidentate nitrate ligands, with the distal N$=$O oxygen atoms coordinating the potassium on the B' site in an octahedral six-coordinate environment. The two-remaining charge-compensating (CH 3 ) 4 N + cations occupy the interstitial voids in the lattice on the A site. This periodic series was characterized via single-crystal X-ray diffraction, powder X-ray diffraction, IR, and Raman spectroscopy. Emission spectra of the Eu complex indicate a phase transition to trigonal symmetry upon cooling. In conclusion, this series is unique as it represents a rare isostructural series spanning the entirety of the rare earth elements excluding promethium with homoleptic 12-coordinate rare earth metal ions.

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

Multiscale Modeling of Plutonium Radiation Chemistry in Nitric Acid Solutions. 1. Cobalt-60 Gamma Irradiation of Pu(IV)

We report careful manipulation of the plutonium oxidation states is essential in the study and utilization of its rich redox chemistry. To achieve this level of control, a comprehensive mechanistic understanding of radiation-induced plutonium redox chemistry is critical due to the unavoidable exposure of plutonium to ionizing radiation fields, both inherent and from in-process applications. To this end, we have developed an experimentally evaluated multiscale computer model for the prediction of gamma radiation-induced Pu(IV) redox chemistry in concentrated nitric acid solutions (1.0, 3.0, and 6.0 M). Under these acidic, aqueous solution conditions, cobalt-60 gamma irradiation afforded marginal net conversion of Pu(IV) to Pu(VI), the extent of which was dependent on the concentration of HNO 3 and absorbed gamma dose. Multiscale calculations, which are in excellent agreement with experimental data, indicate that this observation is due to a combination of inherent plutonium disproportionation reactions and several radiation-induced processes, including redox cycling between Pu(IV) and Pu(III), as achieved by the reduction of Pu(IV) by nitrous acid and hydrogen peroxide, the oxidation of Pu(III) by nitrate and hydroxyl radicals, and the sequential oxidation of Pu(IV) to Pu(V) and Pu(VI) by the remaining available yield of nitrate radicals.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Spectroscopic Properties of Americium(III) in Mineral Acid Media

We report the preparation and optical characterization of three solutions of Am(III) in common aqueous (aq.) mineral acids (HCl, HNO 3 and HBr), including absorption, emission, and Raman vibrational analyses. To our knowledge, this study provides the first detailed absorption spectra of Am(III) spanning the entire UV/Vis/NIR region in these mineral acids reported since the 1960s. Here, using this high-resolution absorption data, provided in an open access format for the broader field, we build on prior work by Carnall and others to provide detailed optical analysis including all transition assignments. This work also includes the first reported absorption spectrum of Am(III) in aq. HBr. Characteristic Am(III) luminescence could be detected from all three samples. These are the first reports of emission from Am(III) in these acid systems, which build on prior emission reports collected from aq. HClO 4 solutions. The acquired emission spectra display anion-dependent shifting of the visible-region transitions by up to 21 nm from their predicted positions, akin to the nephelauxetic effect. The shift magnitude trends linearly according to the acid p K a and more generally according to the transition metal spectrochemical series. These ligand field effects, coupled with luminescence lifetime experiments, indicate that weak Am-X interactions persist in solution.

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

Thermal and Catalytic Decomposition of 2-Hydroxyethylhydrazine and 2-Hydroxyethylhydrazinium Nitrate Ionic Liquid

To develop chemical kinetics models for the combustion of ionic liquid-based monopropellants, identification of the elementary steps in the thermal and catalytic decomposition of components such as 2-hydroxyethylhydrazinium nitrate (HEHN) is needed but is currently not well understood. The first decomposition step in protic ionic liquids such as HEHN is typically the proton transfer from the cation to the anion, resulting in the formation of 2-hydroxyethylhydrazine (HEH) and HNO 3 . In the first part of this investigation, the high-temperature thermal decomposition of HEH is probed with flash pyrolysis (<1400 K) and vacuum ultraviolet (10.45 eV) photoionization time-of-flight mass spectrometry (VUV-PI-TOFMS). Next, the investigation into the thermal and catalytic decomposition of HEHN includes two mass spectrometric techniques: (1) tunable VUV-PI-TOFMS (7.4-15 eV) and (2) ambient ionization mass spectrometry utilizing both plasma and laser ionization techniques whereby HEHN is introduced onto a heated inert or iridium catalytic surface and the products are probed. The products can be identified by their masses, their ionization energies, and their collision-induced fragmentation patterns. Further, formation of product species indicates that catalytic surface recombination is an important reaction process in the decomposition mechanism of HEHN. The products and their possible elementary reaction mechanisms are discussed.

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

Theoretical Kinetics Predictions for Reactions on the NH 2 O Potential Energy Surface

Recent modeling studies of ammonia oxidation, which are motivated by the prospective role of ammonia as a zero-carbon fuel, have indicated significant discrepancies among the existing literature mechanisms. In this study, high-level theoretical kinetics predictions have been obtained for reactions on the NH 2 O potential energy surface, including the NH 2 + O, HNO + H, and NH + OH reactions. These reactions have previously been highlighted as important reactions in NH 3 oxidation with high sensitivity and high uncertainty. The potential energy surface is explored with coupled cluster calculations, including large basis sets and high-level corrections to yield high-accuracy (~0.2 kcal/mol 2σ uncertainty) estimates of the stationary point energies. Variational transition state theory is used to predict the microcanonical rate constants, which are then incorporated in master equation treatments of the temperature- and pressure-dependent kinetics. For radical–radical channels, the microcanonical rates are obtained from variable reaction coordinate transition state theory implementing directly evaluated multireference electronic energies. The analysis yields predictions for the total rate constants as well as the branching ratios. We find that the NO + H 2 channel contributes 10% of the total NH 2 + O flux at combustion temperatures, although this channel is not included in modern NH 3 oxidation mechanisms. Modeling is used to illustrate the ramifications of these rate predictions on the kinetics of NH 3 oxidation and NO x formation. Finally, the present results for NH 2 + O are important for predicting the chain branching and formation of NO in the oxidation of NH 3 and thermal DeNO x .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

The Reaction Rates of Amidogen and Ammonia with Nitrous Oxide: Implications for Combustion Mechanisms

Pulsed laser photolysis experiments with laser-induced fluorescence detection of NH 2 set an upper limit to the rate constant for reaction with N 2 O of k < 1 × 10 −15 cm 3 molecule −1 s −1 at 513 K. Computations were based on geometries and anharmonic frequency analysis (B2PLYP-D3/cc-pVTZ) followed by coupled cluster calculations extrapolated to the infinite basis set limit, with corrections for core−valence electron correlation, scalar relativistic effects, and correlation up to CCSDT(Q). Species that showed multireference character were quantified with MRCI(7,7)+Q/cc-pVTZ theory. Rate constants were obtained for the dominant product channel H 2 NN + NO, along with HN 3 + OH, H 2 NO + N 2 , NNH + HNO, ON(NH) 2 and HNNH + NO. The last channel is slow even at 2500 K, contrary to an early empirical estimate and confirming recent suggestions. Modeling of literature experiments on oxidation of NH 3 by N 2 O shows that all channels are too slow to make a significant impact on the loss of N 2 O in ammonia flames. Similarly, the direct NH 3 + N 2 O reaction is found to be negligibly slow.

Ammonia↗
DOE OSTI2024

DFT Analysis of the Binding of Rare Earth Nitrates at Internal and External Surfaces of MCM-22

MCM-22-type zeolites constitute a well-characterized tunable class of aluminosilicates suitable for elucidating the fundamental aspects of the binding of rare earth elements (REEs) in layered materials. Starting from the pure silica version ITQ-1 with a unit cell of Si 72 O 144 , a model for periodic bulk crystalline MCM-22 with a finite Al concentration is provided by replacing a Si atom with an Al atom in the unit cell at suitable tetrahedral sites near an internal pore surface. Then, a H atom is added to an O atom bridging Si and Al atoms to create a Brønsted acid site (BAS). There are no internal silanol groups in this bulk model. To generate a model for an external surface, we adopt the fully hydroxylated surface structure of a layer within the ITQ-1 precursor with two silanols per lateral unit cell. A BAS on the external surface can be generated by replacing a near-surface Si atom with an Al atom and adding a H atom, as above. The strength of binding at a BAS of REE, X, taken to be present in the solution phase as nitrates, is determined from the energy change in the reaction X(NO 3 ) 3 + ≡Si–{OH}–Al≡ → ≡Si–{OX(NO 3 ) 2 }–Al≡+ HNO 3 . The strength of binding at the silanols is determined similarly. Binding energies are determined from two approaches. The first performs periodic plane-wave density functional theory (DFT) total energy analysis for an entire unit cell of MCM-22. The second utilizes cluster models capturing the local environment of REE binding sites and performs DFT analysis with localized basis sets. The two approaches yield consistent results for Nd, revealing similarly strong binding at either an external or internal BAS, but much weaker binding at a silanol site. This is consistent with the picture deduced from recent experiments. Here, we also comment on binding at Al-bridged siloxane sites, which have been suggested as alternative binding sites to BAS.

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

Fine-Tuning of Pt Dispersion on Al 2 O 3 and Understanding the Nature of Active Pt Sites for Efficient CO and NH 3 Oxidation Reactions

Fine-tuning the dispersion of active metal species on widely used supports is a research hotspot in the catalysis community, which is vital for achieving a balance between the atomic utilization efficiency and the intrinsic activity of active sites. In this work, using bayerite Al(OH) 3 as support directly or after precalcination at 200 or 550 °C, Pt/Al 2 O 3 catalysts with distinct Pt dispersions from single atoms to clusters (ca. 2 nm) were prepared and evaluated for CO and NH 3 removal. Richer surface hydroxyl groups on AlO x (OH) y support were proved to better facilitate the dispersion of Pt. However, Pt/Al 2 O 3 with relatively lower Pt dispersion could exhibit better activity in CO/NH 3 oxidation reactions. Further reaction mechanism study revealed that the Pt sites on Pt/Al 2 O 3 with lower Pt dispersion could be activated to Pt 0 species much easier under the CO oxidation condition, on which a higher CO adsorption capacity and more efficient O 2 activation were achieved simultaneously. Compared to Pt single atoms, PtO x clusters could also better activate NH 3 into –NH 2 and –HNO species. The higher CO adsorption capacity and the more efficient NH 3 /O 2 activation ability on Pt/Al 2 O 3 with relatively lower Pt dispersion well explained its higher CO/NH 3 oxidation activity. This study emphasizes the importance of avoiding a singular pursuit of single-atom catalyst synthesis and instead focusing on achieving the most effective Pt species on Al 2 O 3 support for targeted reactions. Finally, this approach avoids unnecessary limitations and enables a more practical and efficient strategy for Pt catalyst fabrication in emission control applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Electrochemical Behavior of Cerium at an Indium Tin-Doped Oxide Electrode in Acidic Media

The redox behavior and speciation of cerium at mesoporous thin films composed of nanoparticles of indium tin-doped oxide (nITO) electrodes were characterized in pH 4.8, 0.1 M acetate buffer and both 0.1 and 1 M HNO 3 using electrochemical techniques and X-ray photoelectron spectroscopy. Anodic deposition of ceria species from Ce(III) to the nITO electrode was achieved under all solvent conditions via spontaneous condensation of electrochemically generated ceric hydroxide species. In 1 M nitric acid, the rate of CeO 2 dissolution is on the same order as CeO 2 deposition, resulting in negligible amounts of CeO 2 electrodeposited at the nITO surface. The cathodic stripping of CeO 2 from the nITO substrate deposited in 0.1 M nitric acid or pH 4.8 acetate buffer follows a 2-step process where Ce(IV)-oxide is initially reduced to an unstable Ce(III)-oxide species that rapidly undergoes acid catalyzed dissolution to yield soluble Ce(III) (aq) . These findings provide a foundation for the pH and anodic potential controlled deposition of CeO 2 thin films to ITO substrates, which can aid in the development of materials composed of ceria. As a result, they can also be used to infer likely analogous actinide redox behavior and speciation at these electrodes.

Cerium↗
DOE OSTI2020

Characterization of the ALSEP Process at Equilibrium: Speciation and Stoichiometry of the Extracted Complex

We have determined the identity of the complexes extracted into the ALSEP process solvent from solutions of nitric acid. The ALSEP process is a new solvent extraction separation designed to separate americium and curium from trivalent lanthanides in irradiated nuclear fuel. ALSEP employs a mixture of two extractants, 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and N,N,N',N'-tetra(2-ethylhexyl)diglycolamide (TEHDGA) in n-dodecane, which makes it difficult to ascertain the nature of the extracted metal complexes. It is often asserted that the weak acid extractant HEH[EHP] does not participate in the extracted complex under ALSEP extraction conditions (2–4 M HNO 3 ). However, the analysis of the Am extraction equilibria, Nd absorption spectra, and Eu fluorescence emission spectra of metal-loaded organic phases argues for the participation of HEH[EHP] in the extracted complex despite the high acidity of the aqueous phases. The extracted complex was determined to contain fully protonated molecules of HEH[EHP] with an overall stoichiometry of M(TEHDGA) 2 (HEH[EHP]) 2 ·3NO 3 . Computations also demonstrate that replacing one TEHDGA molecule with one (HEH[EHP]) 2 dimer is likely energetically favorable compared to Eu(TEHDGA) 3 ·3NO 3 , whether the HEH[EHP] dimer is monodentate or bidentate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Near-Real-Time Material Tracking: Combining Vis–NIR Spectroscopy with Flow Sensing for Accurate Nd(III) Quantification

A fiber-optic visible–near-infrared (vis–NIR) absorption spectroscopy and flow sensor system has been developed for near-real-time tracking of Nd mass in the effluent stream from a column in a fume hood. The approach leverages two unique data streams and a partial least-squares regression (PLSR) model trained on vis–NIR absorption spectra of Nd(III) (0–1.5 M) in 1 M HNO 3 . In-line volumetric flow rate and vis–NIR spectra are measured in sequence after a chromatography column. The time stamps from each data stream are then synchronized, which allows integrated volumes to be combined with Nd(III) molarities predicted by a PLSR model to accurately calculate the Nd mass flowing through the column. This integrated measurement provides instantaneous mass flow and accumulates these data over time to obtain the total mass processed. The methodology developed in this study contributes critical technical infrastructure to improve monitoring capabilities to support chemical separations and the production of strategic materials and isotopes.

Irvine, Sawyer B. [Oak Ridge National Laboratory (↗
DOE OSTI2024

Reaction Discovery Using Spectroscopic Insights from an Enzymatic C–H Amination Intermediate

Engineered hemoproteins can selectively incorporate nitrogen from nitrene precursors like hydroxylamine, O-substituted hydroxylamines, and organic azides into organic molecules. Although iron-nitrenoids are often invoked as the reactive intermediates in these reactions, their innate reactivity and transient nature have made their characterization challenging. Here we characterize an iron-nitrosyl intermediate generated from NH 2 OH within a protoglobin active site that can undergo nitrogen-group transfer catalysis, using UV–vis, electron paramagnetic resonance (EPR) spectroscopy, and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) techniques. The mechanistic insights gained led to the discovery of aminating reagents—nitrite (NO 2 – ), nitric oxide (NO), and nitroxyl (HNO)—that are new to both nature and synthetic chemistry. Based on the findings, we propose a catalytic cycle for C–H amination inspired by the nitrite reductase pathway. Furthermore, this study highlights the potential of engineered hemoproteins to access natural nitrogen sources for sustainable chemical synthesis and offers a new perspective on the use of biological nitrogen cycle intermediates in biocatalysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Mesh-like structure integrated core-shell-shell nanocomposites for enhanced stability and performance in carbon capture

Carbon capture is essential for mitigating climate change, yet most sorbents struggle to combine high capacity with chemical stability. Here we report core-shell-shell (CSS) nanocomposites that integrate adsorption efficiency with exceptional robustness. The design couples a metal-organic framework (MOF) core, which enriches local CO 2 concentration, with a polyamine shell that is reorganized into a porous, ordered network through entanglement with an outer covalent organic framework (COF) shell. This hierarchical architecture enables dual amine functionalization via sequential “click” and Schiff-base reactions, achieving a CO 2 uptake of 3.4 mmol g −1 at 1 bar. The COF outer layer also acts as a protective barrier, suppressing humidity interference and doubling cycling stability under simulated flue gas. Remarkably, the nanocomposites maintain structural integrity after one week in strongly acidic (3 M HNO 3 ) or basic (NaOH, pH=14) environments, underscoring their chemical resilience. By uniting high capacity, cycling durability, and environmental tolerance, this CSS strategy offers a versatile platform for next-generation carbon capture materials.

Yang, Sizhuo [Lawrence Berkeley National Laborator↗