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Angewandte Chemie | 2013

Seawater Uranium Sorbents: Preparation from a Mesoporous Copolymer Initiator by Atom-Transfer Radical Polymerization†

Yanfeng Yue; Richard T. Mayes; Jungseung Kim; Pasquale F. Fulvio; Xiao-Guang Sun; Costas Tsouris; Jihua Chen; Suree Brown; Sheng Dai

The world s oceans, where uranium is found quite uniformly at a concentration of 3.3 mgL , present an alternative source of uranium to terrestrial mining for nuclear fuel. Environmental concerns associated with mining will undoubtedly increase as reserves are depleted, thus increasing the utility of more environmentally friendly feedstocks. Hence, before terrestrial resources become scarce, the development of sorbents designed for seawater extraction is of strategic importance to guarantee future uranium resources. From the first inorganic adsorbents, which showed poor selectivity and mechanical resistance, to the most recent polyethylene-fiberbased sorbents containing amidoxime–carboxylic acid copolymers, and more recently layered metal sulfides and metal– organic frameworks, interest in uranium seawater extractions has continuously increased among governments worldwide. Because the concentration of uranium in the oceans is relatively low, maximization of the adsorption properties of sorbents, for example, through changes in their surface area and pore structure, can greatly improve the kinetics of uranium extraction and the adsorption capacity simultaneously. To facilitate the uptake of uranyl ions with fast kinetics, various sorbents containing the amidoxime group, such as hydrogels, particles and beads, membranes, macroporous fibers, and composites, have been prepared by suspension polymerization, radiation-induced grafting, and even sonochemical functionalization. However, silica beads and most carbon materials have a relatively small accessible surface area for the growth of large polymers or a low number of surface sites available for the grafting of functional groups. Thus, the design of substrates with large numbers of accessible reactive sites for the grafting of polymeric surface groups is necessary for the development of materials with improved uranium-adsorption capacity. Recently, porous polymers based on divinylbenzene (DVB) have been developed for applications in separations and catalysis. For example, the copolymerization of p-styrene sulfonate with divinylbenzene led to a catalytically active porous polymer. This method has the additional advantage that polymers can be obtained with controlled porosity and high surface areas without porogens. It is thus timeand cost-effective, as well as more environmentally friendly than the templated synthesis of carbonaceous materials. Motivated by these findings, we report herein nanoporous polymers based on the vinylbenzyl chloride (VBC) monomer and the DVB cross-linking agent. As well as a well-developed nanoporous structure of microand mesopores, the obtained polymers contain large numbers of accessible chlorine species, which can be used as initiators for atom-transfer radical polymerization (ATRP). These materials are the first examples of ATRP initiators in which the initiator species is located within the framework of the mesoporous support. The accessible framework and surface chlorine species were used to grow polyacrylonitrile chains, which were then converted into polyamidoxime for uranium adsorption from seawater with tailorable adsorption and surface properties. Three copolymer monoliths were synthesized by freeradical polymerization; that is, the monomer 4-vinylbenzyl chloride was cross-linked by divinylbenzene with 2,2’-azobisisobutyronitrile (AIBN, 98%) as the initiator to give copolymers hereafter referred to as p(xDVB-VBC) (in which x stands for the molar ratio of DVB to VBC). By varying the ratio of the monomer and the cross-linking reactant, it was possible to adjust the pore structure, that is, the surface area and pore volume (Figure 1). Since these adjustments arose from changes in the DVB to VBC ratio, the initiator concentration (i.e. the amount of chloride substituents present) was also varied. The nitrogen isotherms measured at 196 8C for the samples show that nonporous materials as well as materials with tailorable mesopore volumes can be [*] Dr. Y. Yue, Dr. R. T. Mayes, Dr. P. F. Fulvio, Dr. X.-G. Sun, Prof. Dr. S. Dai Chemical Sciences Division, Oak Ridge National Laboratory Oak Ridge, TN 37831 (USA) E-mail: dais@ornl.gov


Journal of the American Chemical Society | 2013

Template-Free Synthesis of Hierarchical Porous Metal-Organic Frameworks

Yanfeng Yue; Zhen-An Qiao; Pasquale F. Fulvio; Andrew J. Binder; Chengcheng Tian; Jihua Chen; Kimberly M. Nelson; Xiang Zhu; Sheng Dai

A template-free synthesis of a hierarchical microporous-mesoporous metal-organic framework (MOF) of zinc(II) 2,5-dihydroxy-1,4-benzenedicarboxylate (Zn-MOF-74) is reported. The surface morphology and porosity of the bimodal materials can be modified by etching the pore walls with various synthesis solvents for different reaction times. This template-free strategy enables the preparation of stable frameworks with mesopores exceeding 15 nm, which was previously unattained in the synthesis of MOFs by the ligand-extension method.


Accounts of Chemical Research | 2015

Hierarchical Metal–Organic Framework Hybrids: Perturbation-Assisted Nanofusion Synthesis

Yanfeng Yue; Pasquale F. Fulvio; Sheng Dai

Metal-organic frameworks (MOFs) represent a new family of microporous materials; however, microporous-mesoporous hierarchical MOF materials have been less investigated because of the lack of simple, reliable methods to introduce mesopores to the crystalline microporous particles. State-of-the-art MOF hierarchical materials have been prepared by ligand extension methods or by using a template, resulting in intrinsic mesopores of longer ligands or replicated pores from template agents, respectively. However, mesoporous MOF materials obtained through ligand extension often collapse in the absence of guest molecules, which dramatically reduces the size of the pore aperture. Although the template-directed strategy allows for the preparation of hierarchical materials with larger mesopores, the latter requires a template removal step, which may result in the collapse of the implemented mesopores. Recently, a general template-free synthesis of hierarchical microporous crystalline frameworks, such as MOFs and Prussian blue analogues (PBAs), has been reported. This new method is based on the kinetically controlled precipitation (perturbation), with simultaneous condensation and redissolution of polymorphic nanocrystallites in the mother liquor. This method further eliminates the use of extended organic ligands and the micropores do not collapse upon removal of trapped guest solvent molecules, thus yielding hierarchical MOF materials with intriguing porosity in the gram scale. The hierarchical MOF materials prepared in this way exhibited exceptional properties when tested for the adsorption of large organic dyes over their corresponding microporous frameworks, due to the enhanced pore accessibility and electrolyte diffusion within the mesopores. As for PBAs, the pore size distribution of these materials can be tailored by changing the metals substituting Fe cations in the PB lattice. For these, the textural mesopores increased from approximately 10 nm for Cu analogue (mesoCuHCF), to 16 nm in Co substituted compound (mesoCoHCF), and to as large as 30 nm for the Ni derivative (mesoNiHCF). While bulk PB and analogues have a higher capacitance than hierarchical analogues for Na-batteries, the increased accessibility to the microporous channels of PBAs allow for faster intercalated ion exchange and diffusion than in bulk PBA crystals. Thus, hierarchical PBAs are promising candidates for electrodes in future electrochemical energy storage devices with faster charge-discharge rates than batteries, namely pseudocapacitors. Finally, this new synthetic method opens the possibility to prepare hierarchical materials having bimodal distribution of mesopores, and to tailor the structural properties of MOFs for different applications, including contrasting agents for MRI, and drug delivery.


Science China-chemistry | 2013

Polymer-coated nanoporous carbons for trace seawater uranium adsorption

Yanfeng Yue; Xiao-Guang Sun; Richard T. Mayes; Jungseung Kim; Pasquale F. Fulvio; Zhen-An Qiao; Suree Brown; Costas Tsouris; Yatsandra Oyola; Sheng Dai

Polymer-coated mesoporous carbon nanocomposites were prepared from the immobilization of acrylonitrile and acrylic acid copolymers with divinylbenzene as a crosslinker onto a mesoporous carbon framework. High surface areas were maintained after polymerization with accessible porosity. This functional nanocomposite was tested as an adsorbent for uranium from high salinity solutions. Uranium adsorption results have shown that the adsorption capacities are strongly influenced by the density of the amidoxime groups and the specific surface area.


Chemsuschem | 2015

Hierarchically Superstructured Prussian Blue Analogues: Spontaneous Assembly Synthesis and Applications as Pseudocapacitive Materials

Yanfeng Yue; Zhiyong Zhang; Andrew J. Binder; Jihua Chen; Xianbo Jin; Steven H. Overbury; Sheng Dai

Hierarchically superstructured Prussian blue analogues (hexacyanoferrate, M=Ni(II) , Co(II) and Cu(II) ) are synthesized through a spontaneous assembly technique. In sharp contrast to macroporous-only Prussian blue analogues, the hierarchically superstructured porous Prussian blue materials are demonstrated to possess a high capacitance, which is similar to those of the conventional hybrid graphene/MnO2 nanostructured textiles. Because sodium or potassium ions are involved in energy storage processes, more environmentally neutral electrolytes can be utilized, making the superstructured porous Prussian blue analogues a great contender for applications as high-performance pseudocapacitors.


RSC Advances | 2015

Macroporous monoliths for trace metal extraction from seawater

Yanfeng Yue; Richard T. Mayes; Gary A. Gill; Li Jung Kuo; Jordana R. Wood; Andrew J. Binder; Suree Brown; Sheng Dai

The viability of seawater-based uranium recovery depends on the uranium adsorption rate and capacity, since the concentration of uranium in the oceans is relatively low (3.3 μg L−1). An important consideration for a fast adsorption is to maximize the adsorption properties of adsorbents such as surface areas and pore structures, which can greatly improve the kinetics of uranium extraction and the adsorption capacity simultaneously. Following this consideration, macroporous monolith adsorbents were prepared from the copolymerization of acrylonitrile (AN) and N,N′-methylene-bis(acrylamide) (MBAAm) based on a cryogel method using both hydrophobic and hydrophilic monomers. The monolithic sorbents were tested with simulated seawater containing a high uranyl concentration (∼6 ppm) and the uranium adsorption results showed that the adsorption capacities are strongly influenced by the ratio of monomer to the crosslinker, i.e., the density of the amidoxime groups. The preliminary seawater testing indicates the high salinity content of seawater does not hinder the adsorption of uranium.


Journal of Materials Chemistry | 2015

A POM–organic framework anode for Li-ion battery

Yanfeng Yue; Yunchao Li; Zhonghe Bi; Gabriel M. Veith; Craig A. Bridges; Bingkun Guo; Jihua Chen; David R. Mullins; Sumedh P. Surwade; Shannon M. Mahurin; Hongjun Liu; M. Parans Paranthaman; Sheng Dai

Rechargeable Li-ion batteries (LIBs) are currently the dominant power source for portable electronic devices and electric vehicles, and for small-scale stationary energy storage. However, one bottleneck of the anode materials for LIBs is the poor cycling performance caused by the fact that the anodes cannot maintain their integrity over several charge–discharge cycles. In this work, we demonstrate an approach to improving the cycling performance of lithium-ion battery anodes by constructing an extended 3D network of flexible redox active polyoxometalate (POM) clusters with redox active organic linkers, herein described as POMOF. This architecture enables the accommodation of large volume changes during cycling at relatively high current rates. For example, the POMOF anode exhibits a high reversible capacity of 540 mA h g−1 after 360 cycles at a current rate of 0.25C and a long cycle life at a current rate of 1.25C (>500 cycles).


CrystEngComm | 2015

Synthesis of metal–organic framework particles and thin films via nanoscopic metal oxide precursors

Yanfeng Yue; Nada Mehio; Andrew J. Binder; Sheng Dai

Metal–organic frameworks (MOFs) are a diverse family of hybrid inorganic–organic crystalline solids synthesized by assembling secondary building units (SBUs) and organic ligands into a periodic and porous framework. Microporous MOF materials, due to their high permeability and size selectivity, have attracted tremendous interest in gas storage and separation, large molecule adsorption, catalysis, and sensing. Despite the significant fabrication challenges, nanosized MOF particles can be fabricated to display enhanced gas storage and separation abilities in comparison to the parent MOF bulk counterparts under special synthesis conditions. So far, the majority of MOF nanocrystals have been derived from the controlled nucleation and growth of molecular precursors in homogeneous solutions. However, synthesis protocols based on nucleation and growth from dilute solution precursors are difficult to adapt to the synthesis of other nanoscopic materials, such as thin film and mixed-matrix membranes, which limits the practical applications of MOFs. This article discusses the current status of synthetic methods that have been utilized to fabricate MOF-based nanoscopic materials and ultrathin membranes from nanoscopic metal oxide precursors.


RSC Advances | 2016

Mesoporous xEr2O3·CoTiO3 composite oxide catalysts for low temperature dehydrogenation of ethylbenzene to styrene using CO2 as a soft oxidant

Yanfeng Yue; Li Zhang; Jihua Chen; Dale K. Hensley; Sheng Dai; Steven H. Overbury

A series of mesoporous xEr2O3·CoTiO3 composite oxide catalysts have been prepared using a template method and tested as a new type of catalyst for the oxidative dehydrogenation of ethylbenzene to styrene by using CO2 as a soft oxidant. Among the catalysts tested, the 0.25Er2O3·CoTiO3 sample with a ratio of 1 : 4 : 4 content and calcined at 600 °C exhibited the highest ethylbenzene conversion (58%) and remarkable styrene selectivity (95%) at low temperature (450 °C).


Angewandte Chemie | 2014

Mesoporous Prussian Blue Analogues: Template‐Free Synthesis and Sodium‐Ion Battery Applications

Yanfeng Yue; Andrew J. Binder; Bingkun Guo; Zhiyong Zhang; Zhen-An Qiao; Chengcheng Tian; Sheng Dai

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Sheng Dai

Oak Ridge National Laboratory

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Jihua Chen

Oak Ridge National Laboratory

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Suree Brown

University of Tennessee

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Costas Tsouris

Oak Ridge National Laboratory

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Pasquale F. Fulvio

Oak Ridge National Laboratory

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Richard T. Mayes

Oak Ridge National Laboratory

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Zhen-An Qiao

University of Tennessee

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Dale K. Hensley

Oak Ridge National Laboratory

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