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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Breaking Barriers in Chalcogenide Perovskite Synthesis: A Generalized Framework for Fabrication of BaMS 3 (M═Ti, Zr, Hf) Materials

Abstract Chalcogenide perovskites have garnered increasing attention as stable, non‐toxic alternatives to lead halide perovskites. However, their conventional synthesis at high temperatures (>1000 °C) has hindered widespread adoption. Recent studies have developed low‐to‐moderate temperature synthesis methods (<600 °C) using reactive precursors, yet a comprehensive understanding of the pivotal factors affecting reproducibility and repeatability remains elusive. This study delineates the critical factors in the low‐temperature synthesis of BaMS 3 (M═Zr, Hf, Ti) compounds and presents a generalized framework. Innovative approaches are developed for synthesizing BaMS 3 compounds using this framework involving organometallics for solution deposition. The molecular precursor routes, employing metal acetylacetonates to generate soluble metal–sulfur bonded complexes and metal–organic compounds to produce soluble metal‐thiolate, metal‐isothiocyanate, and metal‐trithiocarbonate species, are demonstrated to yield carbon‐free BaMS 3 . These methods have achieved the most contiguous films of BaZrS 3 and BaHfS 3 using solution deposition to date. Furthermore, a hybrid solution processing method involving stacking sputter‐deposited Zr and solution‐deposited BaS layers is employed to synthesize a contiguous, oxygen‐free BaZrS 3 film. The diffuse reflectance measurements indicate a direct bandgap of ≈ 1.85 eV for the BaZrS 3 films and ≈ 2.1 eV for the BaHfS 3 film under investigation.

25 ENERGY STORAGE↗
DOE OSTI2019

Quasi-Harmonic Lattice Dynamics of a Prototypical Metal–Organic Framework

Quasi-harmonic lattice-dynamical calculations are performed to investigate the combined effect of temperature and pressure on the structural and mechanical properties of a prototypical metal–organic framework material: MOF-5. The softening upon compression of an A 2 g phonon mode at the Γ point in the high-symmetry F m 3 ¯ m structure is identified, which leads to a symmetry reduction and a group–subgroup phase transition to a low-symmetry F m 3 ¯ phase for compressions larger than 0.8%. The effect of the symmetry reduction on the equation-of-state of MOF-5 is investigated, which provides a static bulk modulus K reducing from 17 to 14 GPa and a corresponding change of K ' (pressure derivative of K ) from positive to negative. The effect of pressure on the negative thermal expansion of the framework and on its mechanical response is analyzed. The evolution of the mechanical anisotropy of MOF-5 as a function of pressure is also determined, which allows identifying the occurrence of a shear-induced mechanical instability at 0.45 GPa.

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

Accelerated Discovery of CH 4 Uptake Capacity Metal–Organic Frameworks Using Bayesian Optimization

Abstract High‐throughput computational studies for discovery of metal–organic frameworks (MOFs) for separations and storage applications are often limited by the costs of computing thermodynamic quantities. Recent such studies at the time of writing may use ab initio results for a narrow selection of MOFs or empirical force‐field methods for larger selections. Here, a proof‐of‐concept study is conducted using Bayesian optimization on CH 4 uptake capacity of hypothetical MOFs for an existing dataset (Wilmer et al., Nature Chem. 2012, 4 , 83). It is shown that less than 0.1% of the database needs to be screened with the Bayesian optimization approach to recover the top candidate MOFs. This opens the possibility for efficient screening of MOF databases using accurate ab initio calculations for future adsorption studies on a minimal subset of MOFs. Furthermore, Bayesian optimization and the surrogate model presented here can offer interpretable material design insights and the framework will be applicable in the context of other target properties.

Taw, Eric↗
DOE OSTI2018

Concerted Bimetallic Nanocluster Synthesis and Encapsulation via Induced Zeolite Framework Demetallation for Shape and Substrate Selective Heterogeneous Catalysis

Abstract Bimetallic nanoparticle encapsulation in microporous zeolite crystals is a promising route for producing catalysts with unprecedented reaction selectivities. Herein, a novel synthetic approach was developed to produce PtZn x nanoclusters encapsulated inside zeolite micropores by introducing Pt 2+ cations into a zincosilicate framework via ion exchange, and subsequent controlled demetallation and alloying with framework Zn. The resulting zeolites featured nanoclusters with sizes of approximately 1 nm, having an interatomic structure corresponding to a PtZn x alloy as confirmed by pair distribution function (PDF) analysis. These materials featured simultaneous shape and substrate specificity demonstrated by the selective production of p ‐chloroaniline from the competitive hydrogenation of p ‐chloronitrobenzene and 1,3‐dimethyl‐5‐nitrobenzene.

Iida, Takayuki↗
DOE OSTI2018

Homo‐Helical Rod Packing as a Path Toward the Highest Density of Guest‐Binding Metal Sites in Metal–Organic Frameworks

Abstract In porous materials, metal sites with coordinate solvents offer opportunities for many applications, especially those promoted by host–guest chemistry, but such sites are especially hard to create for Li‐based materials, because unlike transition metals, lithium does not usually possess a high‐enough coordination number for both framework construction and guest binding. This challenge is addressed by mimicking the functional group ratio and metal‐to‐ligand charge ratio in MOF‐74. A family of rod‐packing lithium–organic frameworks (CPM‐47, CPM‐48, and CPM‐49) were obtained. These materials exhibit an extremely high density of guest‐binding lithium sites. Also unusual is the homo‐helical rod‐packing in the CPM series, as compared to the hetero‐helical rod packing by helices of opposite handedness in MOF‐74. This work demonstrates new chemical and structural possibilities in developing a record‐setting high density of guest‐binding metal sites in inorganic–organic porous materials.

Zhao, Xiang↗
DOE OSTI2018

A Metal–Organic Framework with Tetrahedral Aluminate Sites as a Single‐Ion Li + Solid Electrolyte

Abstract We demonstrate the synthesis of the first anionic aluminum metal–organic framework (MOFs) constructed from tetrahedral AlO 4 sites. Al‐Td‐MOF‐1 was obtained in a simple two‐step synthesis by condensation of 1,4‐dihydroxybenzene and lithium aluminum hydride into an amorphous aluminate framework before applying a solvothermal treatment under basic conditions to obtain the crystalline Al‐Td‐MOF‐1 with a chemical composition of Li[Al(C 6 H 4 O 2 ) 2 ]. The overall Al‐Td‐MOF‐1 structure consists of one‐dimensional chains of alternating edge‐sharing AlO 4 and LiO 4 tetrahedral sites describing unidirectional pore channels with a square window aperture of ≈5×5 Å 2 , best described topologically as a uninodal 6‐coordinated snp rod net. Al‐Td‐MOF‐1 features the highest Li + loading reported to date for a MOF (2.50 wt %) and proved to be an effective single‐ion solid electrolyte. An ionic conductivity of 5.7×10 −5 S cm −1 was measured for Al‐Td‐MOF‐1 and the beneficial contribution of crystallinity was evidenced by an 8‐fold increase in conductivity between the disordered and crystalline material.

Fischer, Sabrina↗
DOE OSTI2018

Controlling Dissolution and Transformation of Zeolitic Imidazolate Frameworks by using Electron‐Beam‐Induced Amorphization

Abstract Amorphous zeolitic imidazolate frameworks (ZIFs) offer promising applications as novel functional materials. Herein, amorphization of ZIF‐L through scanning‐electron‐beam exposure is demonstrated, based on amorphization of individual ZIF‐L crystals. The amorphized ZIF product has drastically increased stability against dissolution in water. An electron dose that allows for complete preservation of amorphous particles after immersion in water is established, resulting in new shapes of amorphous ZIF‐L with spatial control at the sub‐micrometer length scale. Changed water stability as a consequence of scanning‐electron‐beam exposure is demonstrated for three additional metal–organic frameworks (ZIF‐8, Zn(BeIm)OAc, MIL‐101), highlighting the potential use of an electron beam for top‐down MOF patterning. Lastly, recrystallization of ZIF‐L in the presence of linker is studied and shows distinct differences for crystalline and amorphized material.

Conrad, Sabrina↗
DOE OSTI2019

Entropy‐Driven Mechanochemical Synthesis of Polymetallic Zeolitic Imidazolate Frameworks for CO 2 Fixation

Abstract High‐entropy materials refer to a kind of materials in which five or more metal species were incorporated deliberately into a single lattice with random occupancy. Up to now, such a concept has been only restricted to hard materials, such as high‐entropy alloys and ceramics. Herein we report the synthesis of hybrid high‐entropy materials, polymetallic zeolitic imidazolate framework (also named as high‐entropy zeolitic imidazolate framework, HE‐ZIF), via entropy‐driven room‐temperature mechanochemistry. HE‐ZIF contains five metals including Zn II , Co II , Cd II , Ni II , and Cu II which are dispersed in the ZIF structure randomly. Moreover, HE‐ZIF shows enhanced catalytic conversion of CO 2 into carbonate compared with ZIF‐8 presumably a result of the synergistic effect of the five metal ions as Lewis acid in epoxide activation.

Xu, Wei↗
DOE OSTI2019

An Americium‐Containing Metal–Organic Framework: A Platform for Studying Transplutonium Elements

Abstract The synthesis, structure, and spectroscopic characterization of the first transplutonium metal–organic framework (MOF) is described. The preparation and structure of Am‐GWMOF‐6, [Am 2 (C 6 H 8 O 4 ) 3 (H 2 O) 2 ][(C 10 H 8 N 2 )], is analogous to that of the isostructural trivalent lanthanide‐only containing material GWMOF‐6. The presented MOF architecture is used as a platform to probe Am 3+ coordination chemistry and guest‐enhanced luminescent emission, whereas the framework itself provides a means to monitor the effects of self‐irradiation upon crystallinity over time. Presented here is a discussion of these properties and the opportunities that MOFs provide in the structural and spectroscopic study of actinides.

Ridenour, J. August↗
DOE OSTI2020

Rapid Generation of Hierarchically Porous Metal–Organic Frameworks through Laser Photolysis

Abstract Hierarchically porous metal–organic frameworks (HP‐MOFs) facilitate mass transfer due to mesoporosity while preserving the advantage of microporosity. This unique feature endows HP‐MOFs with remarkable application potential in multiple fields. Recently, new methods such as linker labilization for the construction of HP‐MOFs have emerged. To further enrich the synthetic toolkit of MOFs, we report a controlled photolytic removal of linkers to create mesopores within microporous MOFs at tens of milliseconds. Ultraviolet (UV) laser has been applied to eliminate “photolabile” linkers without affecting the overall crystallinity and integrity of the original framework. Presumably, the creation of mesopores can be attributed to the missing‐cluster defects, which can be tuned through varying the time of laser exposure and ratio of photolabile/robust linkers. Upon laser exposure, MOF crystals shrank while metal oxide nanoparticles formed giving rise to the HP‐MOFs. In addition, photolysis can also be utilized for the fabrication of complicated patterns with high precision, paving the way towards MOF lithography, which has enormous potential in sensing and catalysis.

Wang, Kun‐Yu↗
DOE OSTI2022

Simultaneous Control of Pore‐Space Partition and Charge Distribution in Multi‐Modular Metal–Organic Frameworks

Abstract We report here a strategy for making anionic pacs type porous materials by combining pore space partition with charge reallocation. The method uses the first negatively charged pore partition ligand (2,5,8‐tri‐(4‐pyridyl)‐1,3,4,6,7,9‐hexaazaphenalene, H‐tph) that simultaneously enables pore partition and charge reallocation. Over two dozen anionic pacs materials have been made to demonstrate their excellent chemical stability and a high degree of tunability. Notably, Ni 3 ‐bdt‐tph (bdt=1,4‐benzeneditetrazolate) exhibits month‐long water stability, while CoV‐bdt‐tph sets a new benchmark for C 2 H 2 storage capacity under ambient conditions for ionic MOFs. In addition to tunable in‐framework modules, we show feasibility to tune the type and concentration of extra‐framework counter cations and their influence on both stability and capability to separate industrial C 3 H 8 /C 3 H 6 and C 6 H 6 /C 6 H 12 mixtures.

Hong, Anh N.↗
DOE OSTI2022

Superior Metal‐Organic Framework Activation with Dimethyl Ether

Abstract Metal–organic frameworks (MOFs) are demonstrated to be readily activated by treatment with the low surface tension, low boiling point solvent dimethyl ether (DME). The mildness of the method enables access to high surface areas by avoiding structural changes in the framework that often plague thermal activation methods. A distinction from previous methods is that DME activation succeeds for materials with coordinatively unsaturated sites (CUS) and non‐CUS MOFs as well. DME displaces solvent molecules occupying the pores of the MOF as well as those coordinated to metal centers; reducing evacuation temperature by using a coordinating, yet highly volatile guest enables low temperature activation with structural retention as demonstrated surface area measurements that match or exceed existing activation protocols.

Wright, Keenan R.↗
DOE OSTI2023

Solvent‐free Synthesis of Multi‐Module Pore‐Space‐Partitioned Metal‐Organic Frameworks for Gas Separation

Abstract Multi‐module design of framework materials with multiple distinct building blocks has attracted much attention because such materials are more amenable to compositional and geometrical tuning and thus offer more opportunities for property optimization. Few examples are known that use environmentally friendly and cost‐effective solvent‐free method to synthesize such materials. Here, we report the use of solvent‐free method (also modulator‐free) to synthesize a series of multi‐module MOFs with high stability and separation property for C 2 H 2 /CO 2 . The synthesis only requires simple mixing of reactants and short reaction time (2 h). Highly porous and stable materials can be made without any post‐synthetic activation. The success of solvent‐free synthesis of multi‐module MOFs reflects the synergy between different modules, resulting in stable pore‐partitioned materials, despite the fact that other competitive crystallization pathways with simpler framework compositions also exist.

Xiao, Yuchen↗
DOE OSTI2023

Kinetic Control via Binding Sites within the Confined Space of Metal Metalloporphyrin‐Frameworks for Enhanced Shape‐Selectivity Catalysis

Abstract One striking feature of enzyme is its controllable ability to trap substrates via synergistic or cooperative binding in the enzymatic pocket, which renders the shape‐selectivity of product by the confined spatial environment. The success of shape‐selective catalysis relies on the ability of enzyme to tune the thermodynamics and kinetics for chemical reactions. In emulation of enzyme's ability, we showcase herein a targeting strategy with the substrate being anchored on the internal pore wall of metal‐organic frameworks (MOFs), taking full advantage of the sterically kinetic control to achieve shape‐selectivity for the reactions. For this purpose, a series of binding site‐accessible metal metalloporphyrin‐frameworks (MMPFs) have been investigated to shed light on the nature of enzyme‐mimic catalysis. They exhibit a different density of binding sites that are well arranged into the nanospace with corresponding distances of opposite binding sites. Such a structural specificity results in a facile switch in selectivity from an exclusive formation of the thermodynamically stable product to the kinetic product. Thus, the proposed targeting strategy, based on the combination of porous materials and binding events, paves a new way to develop highly efficient heterogeneous catalysts for shifting selectivity.

Zhang, Weijie↗
DOE OSTI2023

Evidence of a Uranium‐Paddlewheel Node in a Catecholate‐Based Metal–Organic Framework

Abstract The interactions between uranium and non‐innocent organic species are an essential component of fundamental uranium redox chemistry. However, they have seldom been explored in the context of multidimensional, porous materials. Uranium‐based metal–organic frameworks (MOFs) offer a new angle to study these interactions, as these self‐assembled species stabilize uranium species through immobilization by organic linkers within a crystalline framework, while potentially providing a method for adjusting metal oxidation state through coordination of non‐innocent linkers. We report the synthesis of the MOF NU‐1700 , assembled from U 4+ ‐paddlewheel nodes and catecholate‐based linkers. We propose this highly unusual structure, which contains two U 4+ ions in a paddlewheel built from four linkers—a first among uranium materials—as a result of extensive characterization via powder X‐ray diffraction (PXRD), sorption, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA), in addition to density functional theory (DFT) calculations.

Knapp, Julia G.↗
DOE OSTI2023

Dominant Role of Hole Transport Pathway in Achieving Record High Photoconductivity in Two‐Dimensional Metal–Organic Frameworks

Abstract Metal–organic frameworks (MOFs) with mobile charges have attracted significant attention due to their potential applications in photoelectric devices, chemical resistance sensors, and catalysis. However, fundamental understanding of the charge transport pathway within the framework and the key properties that determine the performance of conductive MOFs in photoelectric devices remain underexplored. Herein, we report the mechanisms of photoinduced charge transport and electron dynamics in the conductive 2D M−HHTP (M=Cu, Zn or Cu/Zn mixed; HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene) MOFs and their correlation with photoconductivity using the combination of time‐resolved terahertz spectroscopy, optical transient absorption spectroscopy, X‐ray transient absorption spectroscopy, and density functional theory (DFT) calculations. We identify the through‐space hole transport mechanism through the interlayer sheet π–π interaction, where photoinduced hole state resides in HHTP ligand and electronic state is localized at the metal center. Moreover, the photoconductivity of the Cu−HHTP MOF is found to be 65.5 S m −1 , which represents the record high photoconductivity for porous MOF materials based on catecholate ligands.

Wang, Denan↗
DOE OSTI2023

Mixed‐Valence Cu I /Cu III Metal–Organic Frameworks with Non‐innocent Ligand for Multielectron Transfer

Abstract We report two novel three‐dimensional copper‐benzoquinoid metal–organic frameworks (MOFs), [Cu 4 L 3 ] n and [Cu 4 L 3 ⋅ Cu(iq) 3 ] n (LH 4 =1,4‐dicyano‐2,3,5,6‐tetrahydroxybenzene, iq=isoquinoline). Spectroscopic techniques and computational studies reveal the unprecedented mixed valency in MOFs, formal Cu(I)/Cu(III). This is the first time that formally Cu(III) species are witnessed in metal–organic extended solids. The coordination between the mixed‐valence metal and redox‐non‐innocent ligand L, which promotes through‐bond charge transfer between Cu metal sites, allows better metal‐ligand orbital overlap of the d‐π conjugation, leading to strong long‐range delocalization and semiconducting behavior. Our findings highlight the significance of the unique mixed valency between formal Cu(I) and highly‐covalent Cu(III), non‐innocent ligand, and pore environments of these bench stable Cu(III)‐containing frameworks on multielectron transfer and electrochemical properties.

Fu, Shang‐Yuan↗
DOE OSTI2019

Entropy-Driven Mechanochemical Synthesis of Polymetallic Zeolitic Imidazolate Frameworks for CO 2 Fixation

High-entropy materials refer to a kind of materials in which five or more metal species were incorporated deliberately into a single lattice with random occupancy. Up to now, such a concept has been only restricted to hard materials, such as high-entropy alloys and ceramics. Herein we report the synthesis of hybrid high-entropy materials, polymetallic zeolitic imidazolate framework (also named as high-entropy zeolitic imidazolate framework, HE-ZIF), via entropy-driven room-temperature mechanochemistry. HE-ZIF contains five metals including Zn II , Co II , Cd II , Ni II , and Cu II which are dispersed in the ZIF structure randomly. Moreover, HE-ZIF shows enhanced catalytic conversion of CO 2 into carbonate compared with ZIF-8 presumably a result of the synergistic effect of the five metal ions as Lewis acid in epoxide activation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗