Search

Mining uranium from seawater is highly desirable for sustaining the increasing demand for nuclear fuel; however, access to this unparalleled reserve has been limited by competitive adsorption of a wide variety of concentrated competitors, especially vanadium. Herein, we report the creation of a series of uranyl-specific “hooks” and the decoration of them into the nanospace of porous organic polymers to afford uranium nanotraps for seawater uranium extraction. Manipulating the relative distances and angles of amidoxime moieties in the ligands enabled the creation of uranyl-specific “hooks” that feature ultrahigh affinity and selective sequestration of uranium with a distribution coefficient threefold higher compared to that of vanadium, overcoming the long-term challenge of the competing adsorption of vanadium for uranium extraction from seawater. The optimized uranium nanotrap (2.5 mg) can extract more than one-third of the uranium in seawater (5 gallons), affording an enrichment index of 3836 and thus presenting a new benchmark for uranium adsorbent. Moreover, with improved selectivity, the uranium nanotraps could be regenerated using a mild base treatment. The synergistic combination of experimental and theoretical analyses in this study provides a mechanistic approach for optimizing the selectivity of chelators toward analytes of interest., The nanotrap featuring uranyl-specific “hooks” was created, which demonstrates ultrahigh enrichment index in seawater uranium extraction, overcoming the long-term challenge of the competitive adsorption of vanadium.

This paper describes hollow fiber sorbents made of the parent polymer of intrinsic microporosity, PIM-1, using a spinning method designed to control the formation of dense barrier layers followed b...

Iodine radioisotopes released during nuclear fuel reprocessing must be removed from the off-gas stream before discharge. One promising material for iodine capture is reduced silver mordenite (Ag0Z). Nevertheless, the adsorbent's capacity will degrade, or age, over time when the material is exposed to other off-gas constituents. Though the overall impact of aging is known, the underlying physical and chemical processes are not. To examine these processes, Ag0Z samples were prepared and aged in 2% NO2 in dry air and in 1% NO in N2 gas streams at 150 °C for up to six months. Aged samples were then characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray absorption spectroscopy. These techniques show that aging involves two overarching processes: (i) oxidation of the silver nanoparticles present in Ag0Z and (ii) migration of oxidized silver into the mordenite's inner network. Silver on the nanoparticle's surface is oxidized through adsorption of O2, NO, and NO2. Raman spectroscopy and X-ray absorption spectroscopy indicate that nitrates are the primary products of this adsorption. Most of these nitrates migrate into the interior of the mordenite and exchange at framework binding sites, returning silver to its unreduced state (AgZ). The remaining nitrates exist at a persistent concentration without aggregating into bulk-phase AgNO3. X-ray absorption spectroscopy results further indicate that iodine adsorption occurs on not just Ag0Z but also on AgZ and a portion of the nitrates in the system. AgZ adsorbs a sizable quantity of iodine early in the aging process, but its capacity drops rapidly over time. For well-aged samples, nitrates are responsible for up to 95% of mordenite's iodine capacity. These results have enhanced our understanding of the aging process in silver mordenite and are expected to guide the development of superior adsorbents for the capture of radioactive iodine from reprocessing off-gas.

To move nuclear as a primary energy source, uranium resources must be secured beyond what terrestrial reserves can provide. Given the vast quantity of uranium naturally found in the ocean, adsorbent materials have been investigated to recover this vital fuel source. Amidoxime (AO) has been found to be the state-of-the-art functional group for this purpose, however, improvements must still be made to overcome the issues with selectively capturing uranium at such a low concentration found in the ocean. Herein, we report PAF-1 as a platform to study the effects of two amidoxime ligands. The synthesized adsorbents, PAF-1-CH2NHAO and PAF-1-NH(CH2)2AO, with varying chain lengths and grafting degrees, were investigated for their uranium uptakes and kinetic efficiency. PAF-1-NH(CH2)2AO was found to outperform PAF-1-CH2NHAO, with a maximum uptake capacity of 385 mg/g and able to reduce a uranium-spiked solution to ppb level within 10 min. Further studies with PAF-1-NH(CH2)2AO demonstrated effective elution for multiple adsorption cycles and showed promising results for uranium recovery in the diverse composition of a spiked seawater solution. The work presented here moves forward design principles for amidoxime-functionalized ligands and provides scope for strategies to enhance the capture of uranium as a sustainable nuclear fuel source.

Porous catalysts have garnered substantial interest as potential platforms for group-transfer catalysis due to the ability to noncovalently colocalize substrates in proximity to site-isolated react...

Emergence is complex behavior arising from the interactions of many simple constituents that do not display such behavior independently. Polyamidoxime (PAO) uranium adsorbents show such phenomena, as recent works articulate that the polymer binds uranium differently than the monomeric constituents. In order to investigate the origins of this emergent uranium-binding behavior, we synthesized a series of amidoxime polymers with low polydispersity and small molecules with lengths ranging from 1 to 125 repeat units. Following immersion in a uranyl-containing solution, the local, intermediate, and macroscopic structures were investigated by X-ray absorption fine structure (XAFS) spectroscopy, small angle neutron scattering (SANS), and dynamic light scattering (DLS). Fits of the extended XAFS (EXAFS) region revealed a progressive change in uranium coordination environment as a function of polymer molecular weight, identifying chain length as a driving force in emergent metal binding and resolving the controversy over how amidoxime adsorbents bind uranium.

Nature can efficiently recognize specific ions by exerting second-sphere interactions onto well-folded protein scaffolds. However, a considerable challenge remains to artificially manipulate such affinity, while being cost-effective in managing immense amounts of water samples. Here, we propose an effective approach to regulate uranyl capture performance by creating bio-inspired nano-traps, illustrated by constructing chelating moieties into porous frameworks, where the binding motif’s coordinative interaction towards uranyl is enhanced by introducing an assistant group, reminiscent of biological systems. Representatively, the porous framework bearing 2-aminobenzamidoxime is exceptional in sequestering high uranium concentrations with sufficient capacities (530 mg g−1) and trace quantities, including uranium in real seawater (4.36 mg g−1, triple the benchmark). Using a combination of spectroscopic, crystallographic, and theory calculation studies, it is revealed that the amino substituent assists in lowering the charge on uranyl in the complex and serves as a hydrogen bond acceptor, boosting the overall uranyl affinity of amidoxime., Uranium extraction is important for both uranium recovery and nuclear waste management. Here, inspired by the high sensitivity of proteins towards specific metal ions, Ma and colleagues demonstrate that introducing secondary coordination spheres into amidoxime-functionalized porous polymers can enhance their uranyl chelating abilities.

Achieving homogeneous dispersion of nanoporous fillers within membrane architectures remains a great challenge for mixed-matrix membrane (MMMs) technology. Imparting solution processability of nanoporous materials would help advance the development of MMMs for membrane-based gas separations. A mechanochemically assisted oxidative coupling polymerization strategy was used to create a new family of soluble nanoporous polymer networks. The solid-state ball-milling method affords inherent molecular weight control over polymer growth and therefore provides unexpected solubility for the resulting nanoporous frameworks. MMM-based CO2 /CH4 separation performance was significantly accelerated by these new soluble fillers. We anticipate this facile method will facilitate new possibilities for the rational design and synthesis of soluble nanoporous polymer networks and promote their applications in membrane-based gas separations.

This work reports a new strategy toward the design of a new class of supported catalysts with intrinsic high-temperature stabilities through entropy maximization. The use of Pt, Ni, Mg, Cu, Zn, and Co not only enables the active sites to be highly dispersed for high catalytic activity in CO oxidation, but also results in extreme thermal stability (900 °C) owing to the entropy-stabilized behavior inside the metal oxide being able to survive harsh conditions.

The amidoxime group (−RNH2NOH) has long been used to extract uranium from seawater on account of its high affinity toward uranium. The development of tunable sorbent materials for uranium sequestration remains a research priority as well as a significant challenge. Herein, we report the design, synthesis, and uranium sorption properties of bis-amidoxime-functionalized polymeric materials (BAP 1–3). Bifunctional amidoxime monomers were copolymerized with an acrylamide cross-linker to obtain bis-amidoxime incorporation as high as 2 mmol g–1 after five synthetic steps. The resulting sorbents were able to uptake nearly 600 mg of uranium per gram of polymer after 37 days of contact with a seawater simulant containing 8 ppm uranium. Moreover, the polymeric materials exhibited low vanadium uptake with a maximum capacity of 128 mg of vanadium per gram of polymer. This computationally predicted and experimentally realized selectivity of uranium over vanadium, nearly 5 to 1 w/w, is one of the highest reported to da...

Recent research has revealed molecular structure beyond the inner coordination sphere is essential in defining the performance of separation processes; nevertheless, such structure remains largely unexplored. Here we apply small-angle neutron scattering (SANS) and X-ray absorption fine structure (XAFS) spectroscopy to investigate the structure of an ionic liquid system studied for f-block element separations. SANS data reveal dramatic changes in the ionic liquid microstructure (∼150 Å) which we demonstrate can be controlled by judicious selection of counterion. Mesoscale structural features (500 Å) are also observed as a function of metal concentration. XAFS analysis supports formation of extended aggregate structures, similar to those observed in traditional solvent extraction processes, and suggests additional parallels may be drawn from further study. Achieving precise tunability over the intermediate features is an important development in controlling mesoscale structure and realizing advanced new forms of soft matter.

Capture of radioactive iodine is a significant consideration during reprocessing of spent nuclear fuel and disposal of legacy wastes. While silver-exchanged mordenite (AgZ) is widely regarded as a benchmark material for assessing iodine adsorption performance, previous research efforts have largely focused on bulk material properties rather than the underpinning molecular interactions that achieve effective iodine capture. As a result, the fundamental understanding necessary to identify and mitigate deactivation pathways for the recycle of AgZ is not available. We applied X-ray Absorption Fine Structure (XAFS) spectroscopy to investigate AgZ following activation, adsorption of iodine, regeneration, and recycle, observing no appreciable degradation in performance due to the highly controlled conditions under which the AgZ was maintained. Fits of the extended XAFS (EXAFS) data reveal complete formation of Ag0 nanoparticles upon treatment with H2, and confirm the formation of α-AgI within the mordenite chann...

An ultrastable Au nanocatalyst based on a heterostructured perovskite support with high surface area and uniform LaFeO3 nanocoatings was successfully synthesized and tested for CO oxidation. Strikingly, small Au nanoparticles (4–6 nm) are obtained after calcination in air at 700 °C and under reaction conditions. The designed Au catalyst not only possessed extreme sintering resistance but also showed high catalytic activity and stability because of the strong interfacial interaction between Au and the heterostructured perovskite support.

We demonstrate the successful functionalization of a porous aromatic framework for uranium extraction from water as exemplified by grafting PAF-1 with the uranyl chelating amidoxime group. The resultant amidoxime-functionalized PAF-1 (PAF-1-CH2AO) exhibits a high uranium uptake capacity of over 300 mg g–1 and effectively reduces the uranyl concentration from 4.1 ppm to less than 1.0 ppb in aqueous solutions within 90 min, well below the acceptable limit of 30 ppb set by the US Environmental Protection Agency. The local coordination environment of uranium in PAF-1-CH2AO is revealed by X-ray absorption fine structure spectroscopic studies, which suggest the cooperative binding between UO22+ and adjacent amidoxime species.

A rational design and synthesis of covalent organic frameworks (COFs) displaying efficient adsorption of surrogates for common organic pollutants is demonstrated herein. Significantly, the top performing mesoporous triazine-functionalized polyimide COF exhibits superior adsorption of the small dye molecule methylene blue, achieving a maximum adsorption capacity of ∼1691 mg g−1 (∼169 wt %), surpassing the performance of all previously reported nanoporous adsorbents. The experimental results and accompanying in silico simulations suggest that both the size of the organic dye molecules and the intrinsic pore-size effect of the COF material should be taken into account simultaneously for the construction of COF-based adsorbents with efficient dyes adsorption capacities. The structural diversity of COF materials along with the understanding of the encapsulation of organic dyes on COFs holds great promise for developing novel COF adsorbents for the efficient removal of organic pollutants from wastewater. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3470–3478, 2017

A superacid-promoted “knitting” strategy has been developed for the generation of a novel family of hypercrosslinked nanoporous polycarbazoles for efficient CO2 capture. Using trifluoromethanesulfonic acid, a Bronsted superacid, we demonstrate the facile and rapid synthesis of highly porous polycarbazoles with BET surface areas as high as 1688 m2 g−1, and capable of adsorbing 3.5 mmol g−1 of CO2 at 298 K and 1 bar. This impressive result bestows the material with the highest CO2 uptake capacity for all nanoporous carbazolic polymers and ranks among the best by known porous organic polymers under this condition. This innovative approach affords a metal-free alternative to Friedel–Crafts alkylation, and may open up new possibilities for the rational design and synthesis of new hypercrosslinked nanoporous organic networks for carbon capture.

Precise control over the chemical structure of hard-matter materials is a grand challenge of basic science and a prerequisite for the development of advanced catalyst systems. In this work we report the application of a sacrificial metal–organic framework (MOF) template for the synthesis of a porous supported metal oxide catalyst, demonstrating proof-of-concept for a highly generalizable approach to the preparation of new catalyst materials. Application of 2,2′-bipyridine-5,5′-dicarboxylic acid as the organic strut in the Ce MOF precursor results in chelation of Cu2+ and affords isolation of the metal oxide precursor. Following pyrolysis of the template, homogeneously dispersed CuO nanoparticles are formed in the resulting porous CeO2 support. By partially substituting non-chelating 1,1′-biphenyl-4,4′-dicarboxylic acid, the Cu2+ loading and dispersion can be finely tuned, allowing precise control over the CuO/CeO2 interface in the final catalyst system. Characterization by X-ray diffraction, X-ray absorption fine structure spectroscopy, and in situ IR spectroscopy/mass spectrometry confirm control over interface formation to be a function of template composition, constituting the first report of a MOF template being used to control interfacial properties in a supported metal oxide. Using CO oxidation as a model reaction, the system with the greatest number of interfaces possessed the lowest activation energy and better activity under differential conditions, but required higher temperature for catalytic onset and displayed inferior efficiency at 100 °C than systems with higher Cu-loading. This finding is attributable to greater CO adsorption in the more heavily-loaded systems, and indicates catalyst performance for these supported oxide systems to be a function of at least two parameters: size of adsorption site and extent of interface. Optimization of catalyst materials thus requires precise control over synthesis parameters, such as is demonstrated by this MOF-templating method.

Bis-triazine phenanthrolines have shown great promise for f-block metal separations, attributable to their highly preorganized structure, nitrogen donors, and more enhanced covalent bonding with actinides over lanthanides. However, their limited solubility in traditional solvents remains a technological bottleneck. Herein we report our recent work using a simple 2,9-bis(triazine)-1,10-phenanthroline (Me-BTPhen) dissolved in an ionic liquid (IL), demonstrating the efficacy of IL extraction systems for the selective separation of americium from europium, achieving separation factors in excess of 7500 and selectively removing up to 99% of the americium. Characterization of the coordination environment was performed using a combination of X-ray absorption fine structure spectroscopy (XAFS) and density functional theory (DFT) calculations.

An in situ doping strategy has been developed for the generation of a novel family of hexaazatriphenylene-based conjugated triazine frameworks (CTFs) for efficient CO2 capture. The resulting task-specific materials exhibit an exceptionally high CO2 uptake capacity (up to 4.8 mmol g(-1) at 297 K and 1 bar). The synergistic effects of ultrananoporosity and rich N/O codoped CO2-philic sites bestow the framework with the highest CO2 adsorption capacity among known porous organic polymers (POPs). This innovative approach not only enables superior CO2 separation performance but also provides tunable control of surface features on POPs, thereby affording control over bulk material properties. We anticipate this novel strategy will facilitate new possibilities for the rational design and synthesis of nanoporous materials for carbon capture.

Single-atom catalysts (SACs) have shown great potential for achieving superior catalytic activity due to maximizing metal efficiency. The key obstacle in developing SACs lies in the availability of supports that can stabilize SACs. Here we report the first successful development of single gold (Au) atom catalysts supported on high-surface-area hierarchical perovskite oxides. The resulting Au single-atoms are extremely stable at calcination temperatures up to 700 °C in air and under reaction conditions. A high catalytic activity for CO oxidation and distinct self-activating property were also achieved. Furthermore, evidenced by theoretical calculations and experimental studies including X-ray absorption fine structures and in situ Fourier-transform infrared spectra, the surface Au active sites are confirmed to be predominately positively charged. This work provides a generalizable approach to fabricating highly stable Au single-atom catalysts with tunable catalytic performance, and we anticipate that this discovery will facilitate new possibilities for the development of single atom catalysts.

A simple charge modulation approach has been developed to stabilize naked Au clusters on a nanoporous conjugated organic network. Through engineering pore walls with regulated charges, the controllable growth of Au nanoclusters has been realized. The resulting supported catalyst exhibits excellent performance in the aerobic oxidation of alcohols.

Remediation of legacy nuclear waste is one of the greatest challenges faced by the US Department of Energy, with projected cleanup efforts requiring over five decades and hundreds of billions of dollars. New materials are necessary to accelerate waste processing, achieving time and financial savings. Herein we report a peroxide treatment to a Ti metal-organic framework (MOF) and related MOF-templated adsorbents. The resulting materials displayed exceptional affinity for Am(III), achieving distribution coefficients in excess of 105 mL/g, and out-performing state-of-the-art benchmarks monosodium titanate (MST) and peroxo-treated modified MST (mMST) for removal of 85Sr(II) and 239, 240Pu(IV) from legacy nuclear waste simulant.

The development of technology to harvest the uranium dissolved in seawater would enable access to vast quantities of this critical metal for nuclear power generation. Amidoxime polymers are the most promising platforms for achieving this separation, yet the design of advanced adsorbents is hindered by uncertainty regarding the uranium binding mode. In this work we use XAFS to investigate the uranium coordination environment in an amidoxime-phosphonic acid copolymer adsorbent. In contrast to the binding mode predicted computationally and from small molecule studies, a cooperative chelating model is favoured, attributable to emergent behavior resulting from inclusion of amidoxime in the polymer. Samples exposed to seawater also display a feature consistent with a μ(2)-oxo-bridged transition metal, suggesting the formation of an in situ specific binding site. These findings challenge long held assumptions and provide new opportunities for the design of advanced adsorbent materials.

Limited resource availability and population growth have motivated interest in harvesting valuable metals from unconventional reserves, but developing selective adsorbents for this task requires structural knowledge of metal binding environments. Amidoxime polymers have been identified as the most promising platform for large-scale extraction of uranium from seawater. However, despite more than 30 years of research, the uranyl coordination environment on these adsorbents has not been positively identified. We report the first XAFS investigation of polyamidoxime-bound uranyl, with EXAFS fits suggesting a cooperative chelating model, rather than the tridentate or η2 motifs proposed by small molecule and computational studies. Samples exposed to environmental seawater also display a feature consistent with a μ2-oxo-bridged transition metal in the uranyl coordination sphere, suggesting in situ formation of a specific binding site or mineralization of uranium on the polymer surface. These unexpected findings challenge several long-held assumptions and have significant implications for development of polymer adsorbents with high selectivity.

Informed by density functional theory calculations, a novel bifunctional chelator, (Z)-2-[2-(N′-hydroxycarbamimidoyl)phenoxy]benzoic acid, was designed and synthesized for ultrahigh uranium uptake from seawater. Investigation of the ligand for uranium sorption was conducted in artificial seawater (pH = 8.2). An exceptional uranium uptake of 553 mg of uranium (g of sorbent)−1 was obtained with a theoretical saturation capacity of 710 mg g–1 obtained by fitting isotherm data with the Langmuir–Freundlich model. The resulting yellow precipitate was characterized via X-ray absorption fine structure (XAFS) at the U LIII-edge, with the extended XAFS spectra best fitted by a model where uranyl is coordinated by monodentate amidoxime, one chelating carboxylic acid, and two water molecules. These results are consistent with the formation of a uranium coordination polymer. The ultrahigh uranium uptake capacity obtained by the bifunctional chelating ligand makes it a promising candidate for deployment as a uranium ad...

In order to ensure a sustainable reserve of fuel for nuclear power generation, tremendous research efforts have been devoted to developing advanced sorbent materials for extracting uranium from seawater. In this work, a porous aromatic framework (PAF) was surface-functionalized with poly(acrylonitrile) through atom-transfer radical polymerization (ATRP). Batches of this adsorbent were conditioned with potassium hydroxide (KOH) at room temperature or 80 °C prior to contact with a uranium-spiked seawater simulant, with minimal differences in uptake observed as a function of conditioning temperature. A maximum capacity of 4.81 g-U/kg-ads was obtained following 42 days contact with uranium-spiked filtered environmental seawater, which demonstrates a comparable adsorption rate. A kinetic investigation revealed extremely rapid uranyl uptake, with more than 80% saturation reached within 14 days. Relying on the semiordered structure of the PAF adsorbent, density functional theory (DFT) calculations reveal coopera...

More than 1000× uranium exists in the oceans than exists in terrestrial ores. With nuclear power generation expected to increase over the coming decades, access to this unconventional reserve is a matter of energy security. With origins in the mid-1950s, materials have been developed for the selective recovery of seawater uranium for more than six decades, with a renewed interest in particular since 2010. This review comprehensively surveys materials developed from 2000–2016 for recovery of seawater uranium, in particular including recent developments in inorganic materials; polymer adsorbents and related research pertaining to amidoxime; and nanostructured materials such as metal–organic frameworks, porous-organic polymers, and mesoporous carbons. Challenges of performing reliable and reproducible uranium adsorption studies are also discussed, as well as the standardization of parameters necessary to ensure valid comparisons between different adsorbents.

Amidoxime-functionalized polymeric adsorbents are the current state-of-the-art materials for collecting uranium (U) from seawater. However, marine tests show that vanadium (V) is preferentially extracted over U and many other cations. Herein, we report a complementary and comprehensive investigation integrating ab initio simulations with thermochemical titrations and XAFS spectroscopy to understand the unusually strong and selective binding of V by polyamidoximes. While the open-chain amidoxime functionalities do not bind V, the cyclic imide-dioxime group of the adsorbent forms a peculiar non-oxido V5+ complex, exhibiting the highest stability constant value ever observed for the V5+ species. XAFS analysis of adsorbents following deployment in environmental seawater confirms V binding solely by the imide-dioximes. Our fundamental findings offer not only guidance for future optimization of selectivity in amidoxime-based sorbent materials, but may also afford insight to understanding the extensive accumulation of V in some marine organisms., Amidoxime-functionalized polymeric adsorbents are the most promising materials for harvesting uranium from seawater. Here the authors investigate the preferential extraction of vanadium over uranium by polyamidoximes by exploring the unusually strong and selective binding of vanadium.

Achieving homogeneous dispersion of nanoporous fillers within membrane architectures remains a great challenge for mixed-matrix membrane (MMMs) technology. Imparting solution processability of nanoporous materials would help advance the development of MMMs for membrane-based gas separations. A mechanochemically assisted oxidative coupling polymerization strategy was used to create a new family of soluble nanoporous polymer networks. The solid-state ball-milling method affords inherent molecular weight control over polymer growth and therefore provides unexpected solubility for the resulting nanoporous frameworks. MMM-based CO

A superacid-promoted "knitting" strategy has been developed for the generation of a novel family of hypercrosslinked nanoporous polycarbazoles for efficient CO

A key challenge in environmental remediation is the design of adsorbents bearing an abundance of accessible chelating sites with high affinity, to achieve both rapid uptake and high capacity for the contaminants. Herein, we demonstrate how two-dimensional covalent organic frameworks (COFs) with well-defined mesopore structures display the right combination of properties to serve as a scaffold for decorating coordination sites to create ideal adsorbents. The proof-of-concept design is illustrated by modifying sulfur derivatives on a newly designed vinyl-functionalized mesoporous COF (COF-V) via thiol–ene “click” reaction. Representatively, the material (COF-S-SH) synthesized by treating COF-V with 1,2-ethanedithiol exhibits high efficiency in removing mercury from aqueous solutions and the air, affording Hg2+ and Hg0 capacities of 1350 and 863 mg g–1, respectively, surpassing all those of thiol and thioether functionalized materials reported thus far. More significantly, COF-S-SH demonstrates an ultrahigh ...

Transition-metal-catalyzed cyanation of aryl halides is a common route to benzonitriles, which are integral to many industrial procedures. However, traditional homogeneous catalysts for such processes are expensive and suffer poor recyclability, so a heterogeneous analogue is highly desired. A novel spatial modulation approach has been developed to fabricate a heterogeneous Pd-metalated nanoporous polymer, which catalyzes the cyanation of aryl halides without need for ligands. The catalyst displays high activity in the synthesis of benzonitriles, including high product yields, excellent stability and recycling, and broad functional-group tolerance.

An innovative wet-treatment with Na2 S transforms two indium metal-organic frameworks (MOFs) into a series of porous inorganic sorbents. These MOF-templated materials display remarkable affinity for heavy metals with saturation occurring in less than 1 h. The saturation capacity for Hg(II) exceeds 2 g g(-1) , more than doubling the best thiol-functionalized sorbents in the literature.

A robust and porous Zr metal-organic framework, sal-MOF, of UiO topology was synthesized using a salicylaldimine (sal)-derived dicarboxylate bridging ligand. Postsynthetic metalation of sal-MOF with iron(II) or cobalt(II) chloride followed by treatment with NaBEt3H in THF resulted in Fe- and Co-functionalized MOFs (sal-M-MOF, M = Fe, Co) which are highly active solid catalysts for alkene hydrogenation. Impressively, sal-Fe-MOF displayed very high turnover numbers of up to 145000 and was recycled and reused more than 15 times. This work highlights the unique opportunity of developing MOF-based earth-abundant catalysts for sustainable chemical synthesis.

Innovative solid-phase sorbent technologies are needed to extract radionuclides from harsh media for environmental remediation and in order to close the nuclear fuel cycle. Highly porous inorganic materials with remarkable sorptive properties have been prepared by topotactic transformations of metal–organic frameworks (MOFs) using both basic and acidic solutions. Treatment of Ti and Zr nanoMOFs with NaOH, Na3PO4, and H3PO4 yields Ti and Zr oxides, oxyphosphates, and phosphates via sacrificial removal of the organic ligands. This controlled ligand extraction process results in porous inorganic materials, which preserve the original MOF morphologies and impart useful surface functionalities, but are devoid of organic linkers. Structural investigation by X-ray absorption spectroscopy reveals preservation of the coordination environment of the scattering metal. Changing the MOF template introduces different metal and structural possibilities, while application of different digest solutions allows preparation ...

A series of new mesoporous silica (MS) sorbents were developed by functionalizing a large-pore 2-D hexagonal MS material, MSU-H, with amidoxime, imide dioxime, phosphonate, and carboxylate functional groups, and characterized by nitrogen adsorption, ζ-potential, infrared spectroscopy, and thermogravimetric analysis. These MS materials have a grafting density of 0.75 to 1.38 mmol/g, and exhibit BET surface areas of 186–526 m 2 /g and average pore sizes of 3.8–7.8 nm. The uranyl sorption by the functionalized MS sorbents was investigated in basic water and artificial seawater at pH = 8.3 ± 0.1. The MS materials exhibited a high U sorption capacity in water (>40 μg U/mg sorbent) with Langmuir isotherms suggesting a saturation U sorption capacity of 185.2 μg U/mg sorbent for the phosphonic acid-modified MS material (MSPh-III). The U sorption capacity in artificial seawater was reduced to 12.1 μg U/mg sorbent for MSPh-III. Langmuir isotherms indicated a saturation sorption capacity of 66.7 μg U/mg sorbent for MSPh-III, which also had the greatest binding affinity for U of all sorbents tested, followed by the imide dioxime-functionalized material MSCA-I. Kinetics studies show rapid uranyl sorption and equilibration in less than 40 min. The U was quantitatively eluted from the MS sorbents by washing with strong acid (>0.1 M HCl). This work represents the first comprehensive study of organo-functionalized MS materials for U extraction, and shows that phosphonic acid- and imide dioxime-functionalized MS materials provide excellent platforms for developing novel sorbents for efficient U extraction from seawater.

A series of functionalized mesoporous carbon (MC) materials were prepared by covalent grafting with amidoxime, carboxyl, and phosphoryl functional groups and screened for uranium (U) sorption from aqueous media. The MC materials were characterized by nitrogen adsorption measurements and thermogravimetric analysis and investigated for U(VI) extraction from both acidic water (pH 4) and artificial seawater (pH 8.2). Under both conditions, a phosphoric acid-functionalized MC exhibited the highest U(VI) sorption, with a maximum sorption capacity of 97 mg of U(VI)/(g of sorbent) in acidic water and 67 mg of U(VI)/(g of sorbent) in artificial seawater. The effects of pH on U(VI) sorption, sorption kinetics, and sorption isotherms were obtained for the phosphoric acid-functionalized MC. Quantitative U(VI) removal from U(VI)-loaded sorbents was achieved by washing with HCl at concentrations higher than 0.01 M. These results indicate that functionalized MC provides a promising platform for the development of novel ...

A novel immunomagnetic method has been developed for the simultaneous measurement of organophosphorus nerve agent (OPNA) adducts to butyrylcholinesterase (BuChE) and free OPNAs in serum. This new approach, deemed dual-mode immunomagnetic analysis (Dual-Mode IMA), combines immunomagnetic separation (IMS) and immunomagnetic scavenging (IMSc) and has been used to measure the effectiveness of cholinesterase reactivators on OPNA-inhibited BuChE in serum. BuChE inhibited by the nerve agent VX, uninhibited BuChE, and unbound VX were measured up to 1 h after the addition of oxime reactivators pralidoxime (2-PAM) and obidoxime. IMS experiments consisted of extracting BuChE and VX-BuChE serum adducts using antibutyrylcholinesterase monoclonal antibodies conjugated to protein-G ferromagnetic particles. In a parallel set of experiments using IMSc, BuChE-coated magnetic beads were used to extract free VX from protein-depleted serum. Adducts from both IMS and IMSc were analyzed using a published IMS liquid chromatography tandem mass spectrometry (IMS-LC-MS/MS) protocol, which has also been demonstrated with other OPNAs. By applying this Dual-Mode IMA approach, 2-PAM was observed to be more potent than obidoxime in reactivating VX-adducted BuChE. VX-BuChE peptide concentrations initially measured at 19.7 ± 0.7 ng/mL decreased over 1 h to 10.6 ± 0.6 ng/mL when reactivated with 2-PAM and 14.4 ± 1.2 ng/mL when reactivated with obidoxime. These experiments also show that previously published IMS-LC-MS/MS analyses are compatible with serum treated with oximes. Dual-Mode IMA is the first immunoaffinity method developed for the simultaneous measurement of OPNA adducted BuChE, unadducted BuChE, and free nerve agent in serum and is a promising new tool for studying reactivator effectiveness on cholinesterases inhibited by nerve agents.

The design and synthesis of metal-free heterogeneous catalysts for efficient hydrogenation remains a great challenge. Here we report a novel approach to create conjugated nanoporous polymers with efficient hydrogenation activities toward unsaturated ketones by leveraging the innate steric encumbrance. The steric bulk of the framework as well as the local sterics of the Lewis basic sites within the polymeric skeleton result in the generation of the putative catalyst. This approach opens up new possibilities for the development of innovative metal-free heterogeneous catalysts.

The catalysts are recycled and reused in up to ten catalytic cycles without loss of activity.

We have designed a strategy for postsynthesis installation of the β-diketiminate (NacNac) functionality in a metal-organic framework (MOF) of UiO-topology. Metalation of the NacNac-MOF (I) with earth-abundant metal salts afforded the desired MOF-supported NacNac-M complexes (M = Fe, Cu, and Co) with coordination environments established by detailed EXAFS studies. The NacNac-Fe-MOF catalyst, I•Fe(Me), efficiently catalyzed the challenging intramolecular sp(3) C-H amination of a series of alkyl azides to afford α-substituted pyrrolidines. The NacNac-Cu-MOF catalyst, I•Cu(THF), was effective in promoting the intermolecular sp(3) C-H amination of cyclohexene using unprotected anilines to provide access to secondary amines in excellent selectivity. Finally, the NacNac-Co-MOF catalyst, I•Co(H), was used to catalyze alkene hydrogenation with turnover numbers (TONs) as high as 700,000. All of the NacNac-M-MOF catalysts were more effective than their analogous homogeneous catalysts and could be recycled and reused without a noticeable decrease in yield. The NacNac-MOFs thus provide a novel platform for engineering recyclable earth-abundant-element-based single-site solid catalysts for many important organic transformations.

The potential consequences of nuclear events and the complexity of nuclear waste management motivate the development of selective solid-phase sorbents to provide enhanced protection. Herein, it is shown that 2D covalent organic frameworks (COFs) with unique structures possess all the traits to be well suited as a platform for the deployment of highly efficient sorbents such that they exhibit remarkable performance, as demonstrated by uranium capture. The chelating groups laced on the open 1D channels exhibit exceptional accessibility, allowing significantly higher utilization efficiency. In addition, the 2D extended polygons packed closely in an eclipsed fashion bring chelating groups in adjacent layers parallel to each other, which may facilitate their cooperation, thereby leading to high affinity toward specific ions. As a result, the amidoxime-functionalized COFs far outperform their corresponding amorphous analogs in terms of adsorption capacities, kinetics, and affinities. Specifically, COF-TpAb-AO is able to reduce various uranium contaminated water samples from 1 ppm to less than 0.1 ppb within several minutes, well below the drinking water limit (30 ppb), as well as mine uranium from spiked seawater with an exceptionally high uptake capacity of 127 mg g-1 . These results delineate important synthetic advances toward the implementation of COFs in environmental remediation.

The first chiral rhodium-diene-based metal–organic frameworks are highly active and enantioselective catalysts for C–C bond formation reactions., We have designed the first chiral diene-based metal–organic framework (MOF), E2-MOF, and postsynthetically metalated E2-MOF with Rh(i) complexes to afford highly active and enantioselective single-site solid catalysts for C–C bond formation reactions. Treatment of E2-MOF with [RhCl(C2H4)2]2 led to a highly enantioselective catalyst for 1,4-additions of arylboronic acids to α,β-unsaturated ketones, whereas treatment of E2-MOF with Rh(acac)(C2H4)2 afforded a highly efficient catalyst for the asymmetric 1,2-additions of arylboronic acids to aldimines. Interestingly, E2-MOF·Rh(acac) showed higher activity and enantioselectivity than the homogeneous control catalyst, likely due to the formation of a true single-site catalyst in the MOF. E2-MOF·Rh(acac) was also successfully recycled and reused at least seven times without loss of yield and enantioselectivity.