Atomically Dispersed Fe/N-Doped Hierarchical Carbon Architectures Derived from a Metal–Organic Framework Composite for Extremely Efficient Electrocatalysis

Hierarchical graphitic porous carbon architectures with atomically dispersed Fe and N doping have been fabricated from a metal–organic framework (MOF) composite by using a facile strategy, which show high specific surface areas, hierarchical pore structures with macro/meso/micro multimodal pore size distributions, abundant surface functionality with single-atom dispersed N and Fe doping, and improved hydrophilicity. Detailed analyses unambiguously disclosed the main active sites of doped N atoms and FeNx species in the catalyst. The resultant catalyst affords high catalytic performance for oxygen reduction, outperforming the benchmark Pt catalyst and many state-of-the-art noble-metal-free catalysts in alkaline media, particularly in terms of the onset and half-wave potentials and durability. Such catalytic performance demonstrates the significant advantages of the unique hierarchical porous structure with efficient atomic doping, which provides a high density of accessible active sites for much improved mass and charge transports

AQDS Activates Extracellular Synergistic Biodetoxification of Copper and Selenite via Altering the Coordination Environment of Outer-Membrane Proteins

The biotransformation of heavy metals in the environment is usually affected by co-existing pollutants like selenium (Se), which may lower the ecotoxicity of heavy metals, but the underlying mechanisms remain unclear. Here, we shed light on the pathways of copper (Cu2+) and selenite (SeO32–) synergistic biodetoxification by Shewanella oneidensis MR-1 and illustrate how such processes are affected by anthraquinone-2,6-disulfonate (AQDS), an analogue of humic substances. We observed the formation of copper selenide nanoparticles (Cu2–xSe) from synergistic detoxification of Cu2+ and SeO32– in the periplasm. Interestingly, adding AQDS triggered a fundamental transition from periplasmic to extracellular reaction, enabling 14.7-fold faster Cu2+ biodetoxification (via mediated electron transfer) and 11.4-fold faster SeO32– detoxification (via direct electron transfer). This is mainly attributed to the slightly raised redox potential of the heme center of AQDS-coordinated outer-membrane proteins that accelerates electron efflux from the cells. Our work offers a fundamental understanding of the synergistic detoxification of heavy metals and Se in a complicated environmental matrix and unveils an unexpected role of AQDS beyond electron mediation, which may guide the development of more efficient environmental remediation and resource recovery biotechnologies

New Insight of Coordination and Extraction of Uranium(VI) with N‑Donating Ligands in Room Temperature Ionic Liquids: <i>N</i>,<i>N</i>′-Diethyl-<i>N</i>,<i>N</i>′-ditolyldipicolinamide as a Case Study

Room temperature ionic liquids (RTILs) represent a recent new class of solvents applied in liquid/liquid extraction based nuclear fuel reprocessing, whereas the related coordination chemistry and detailed extraction processes are still not well understood and remain of deep fundamental interest. The work herein provides a new insight of coordination and extraction of uranium­(VI) with N-donating ligands, e.g., <i>N</i>,<i>N</i>′-diethyl-<i>N</i>,<i>N</i>′-ditolyldipicolinamide (Et_pTDPA), in commonly used RTILs. Exploration of the extraction mechanism, speciation analyses of the extracted U­(VI), and crystallographic studies of the interactions of Et_pTDPA with U­(VI) were performed, including the first structurally characterized UO₂(Et_pTDPA)₂(NTf₂) and UO₂(Et_pTDPA)₂(PF₆)₂ compounds and a first case of crystallographic differentiation between the extracted U­(VI) complexes in RTILs and in molecular solvents. It was found that in RTILs two Et_pTDPA molecules coordinate with one U­(VI) ion through the carbonyl and pyridine nitrogen moieties, while NTf₂^– and PF₆^– act as counterions. The absence of NO₃^– in the complexes is coincident with a cation-exchange extraction. In contrast, both the extracted species and extraction mechanisms are greatly different in dichloromethane, in which UO₂²⁺ coordinates in a neutral complex form with one Et_pTDPA molecule and two NO₃^– cations. In addition, the complex formation in RTILs is independent of the cation exchange since incorporating UO₂(NO₃)₂, Et_pTDPA, and LiNTf₂ or KPF₆ in a solution also produces the same complex as that in RTILs, revealing the important roles of weakly coordinating anions on the coordination chemistry between U­(VI) and Et_pTDPA. These findings suggest that cation-exchange extraction mode for ILs-based extraction system probably originates from the supply of weakly coordinating anions from RTILs. Thus the coordination of uranium­(VI) with extractants as well as the cation-exchange extraction mode may be potentially changed by varying the counterions of uranyl or introducing extra anions

Rational Construction of Porous Metal–Organic Frameworks for Uranium(VI) Extraction: The Strong Periodic Tendency with a Metal Node

Although metal–organic frameworks (MOFs) have been reported as important porous materials for the potential utility in metal ion separation, coordinating the functionality, structure, and component of MOFs remains a great challenge. Herein, a series of anionic rare earth MOFs (RE-MOFs) were synthesized via a solvothermal template reaction and for the first time explored for uranium­(VI) capture from an acidic medium. The unusually high extraction capacity of UO22+ (e.g., 538 mg U per g of Y-MOF) was achieved through ion-exchange with the concomitant release of Me2NH2+, during which the uranium­(VI) extraction in the series of isostructural RE-MOFs was found to be highly sensitive to the ionic radii of the metal nodes. That is, the uranium­(VI) adsorption capacities continuously increased as the ionic radii decreased. In-depth mechanism insight was obtained from molecular dynamics simulations, suggesting that both the accessible pore volume of the MOFs and hydrogen-bonding interactions contribute to the strong periodic tendency of uranium­(VI) extraction

New Insight of Coordination and Extraction of Uranium(VI) with N‑Donating Ligands in Room Temperature Ionic Liquids: <i>N</i>,<i>N</i>′-Diethyl-<i>N</i>,<i>N</i>′-ditolyldipicolinamide as a Case Study

Room temperature ionic liquids (RTILs) represent a recent new class of solvents applied in liquid/liquid extraction based nuclear fuel reprocessing, whereas the related coordination chemistry and detailed extraction processes are still not well understood and remain of deep fundamental interest. The work herein provides a new insight of coordination and extraction of uranium­(VI) with N-donating ligands, e.g., <i>N</i>,<i>N</i>′-diethyl-<i>N</i>,<i>N</i>′-ditolyldipicolinamide (Et_pTDPA), in commonly used RTILs. Exploration of the extraction mechanism, speciation analyses of the extracted U­(VI), and crystallographic studies of the interactions of Et_pTDPA with U­(VI) were performed, including the first structurally characterized UO₂(Et_pTDPA)₂(NTf₂) and UO₂(Et_pTDPA)₂(PF₆)₂ compounds and a first case of crystallographic differentiation between the extracted U­(VI) complexes in RTILs and in molecular solvents. It was found that in RTILs two Et_pTDPA molecules coordinate with one U­(VI) ion through the carbonyl and pyridine nitrogen moieties, while NTf₂^– and PF₆^– act as counterions. The absence of NO₃^– in the complexes is coincident with a cation-exchange extraction. In contrast, both the extracted species and extraction mechanisms are greatly different in dichloromethane, in which UO₂²⁺ coordinates in a neutral complex form with one Et_pTDPA molecule and two NO₃^– cations. In addition, the complex formation in RTILs is independent of the cation exchange since incorporating UO₂(NO₃)₂, Et_pTDPA, and LiNTf₂ or KPF₆ in a solution also produces the same complex as that in RTILs, revealing the important roles of weakly coordinating anions on the coordination chemistry between U­(VI) and Et_pTDPA. These findings suggest that cation-exchange extraction mode for ILs-based extraction system probably originates from the supply of weakly coordinating anions from RTILs. Thus the coordination of uranium­(VI) with extractants as well as the cation-exchange extraction mode may be potentially changed by varying the counterions of uranyl or introducing extra anions

Introduction of Bifunctional Groups into Mesoporous Silica for Enhancing Uptake of Thorium(IV) from Aqueous Solution

The potential industrial application of thorium (Th), as well as the environmental and human healthy problems caused by thorium, promotes the development of reliable methods for the separation and removal of Th­(IV) from environmental and geological samples. Herein, the phosphonate-amino bifunctionalized mesoporous silica (PAMS) was fabricated by a one-step self-assembly approach for enhancing Th­(IV) uptake from aqueous solution. The synthesized sorbent was found to possess ordered mesoporous structures with uniform pore diameter and large surface area, characterized by SEM, XRD, and N₂ sorption/desorption measurements. The enhancement of Th­(IV) uptake by PAMS was achieved by coupling of an access mechanism to a complexation mechanism, and the sorption can be optimized by adjusting the coverage of the functional groups in the PAMS sorbent. The systemic study on Th­(IV) sorption/desorption by using one coverage of PAMS (PAMS12) shows that the Th­(IV) sorption by PAMS is fast with equilibrium time of less than 1 h, and the sorption capacity is more than 160 mg/g at a relatively low pH. The sorption isotherm has been successfully modeled by the Langmuir isotherm and D-R isotherm, which reveals a monolayer homogeneous chemisorption of Th­(IV) in PAMS. The Th­(IV) sorption by PAMS is pH dependent but ionic strength independent. In addition, the sorbed Th­(IV) can be completely desorbed using 0.2 mol/L or more concentrated nitric acid solution. The sorption test performed in the solution containing a range of competing metal ions suggests that the PAMS sorbent has a desirable selectivity for Th­(IV) ions

Bismuth-doping boosting Na⁺ diffusion kinetics of layered oxide cathode with radially oriented {010} active lattice facet for sodium-ion batteries

O3-type layered oxide cathodes (NaxTMO2) for sodium-ion batteries (SIBs) have attracted significant attention as one of the most promising potential candidates for practical energy storage applications. The poor Na+ diffusion kinetics is, however, one of the major obstacles to advancing large-scale practical application. Herein, we report bismuth-doped O3-NaNi0.5Mn0.5O2 (NMB) microspheres consisting of unique primary nanoplatelets with the radially oriented {010} active lattice facets. The NMB combines the advantages of the oriented and exposed electrochemical active planes for direct paths of Na+ diffusion, and the thick primary nanoplatelets for less surface parasitic reactions with the electrolyte. Consequently, the NMB cathode exhibits a long-term stability with an excellent capacity retention of 72.5% at 1C after 300 cycles and an enhanced rate capability at a 0.1C to 10C rate (1C = 240 mA g–1). Furthermore, the enhancement is elucidated by the small volume change, thin cathode-electrolyte-interphase (CEI) layer, and rapid Na+ diffusion kinetics. In particular, the radial orientation-based Bi-doping strategy is demonstrated to be effective at boosting electrochemical performance in other layered oxides (such as Bi-doped NaNi0.45Mn0.45Ti0.1O2 and NaNi1/3Fe1/3Mn1/3O2). The results provide a promising strategy of utilizing the advantages of the oriented active facets of primary platelets and secondary particles to develop high-rate layered oxide cathodes for SIBs

Doping-Enhanced Short-Range Order of Perovskite Nanocrystals for Near-Unity Violet Luminescence Quantum Yield

All-inorganic perovskite nanocrystals (NCs) have emerged as a new generation of low-cost semiconducting luminescent system for optoelectronic applications. The room-temperature photoluminescence quantum yields (PLQYs) of these NCs in the green and red spectral range approach unity. However, their PLQYs in the violet are much lower, and an insightful understanding of such poor performance remains missing. We report a general strategy for the synthesis of all-inorganic violet-emitting perovskite NCs with near-unity PLQYs through engineering local order of the lattice by nickel ion doping. A broad range of experimental characterizations, including steady-state and time-resolved luminescence spectroscopy, X-ray absorption spectra, and magic angle spinning nuclear magnetic resonance spectra, reveal that the low PLQY in undoped NCs is associated with short-range disorder of the lattice induced by intrinsic defects such as halide vacancies and that Ni doping can substantially eliminate these defects and result in increased short-range order of the lattice. Density functional theory calculations reveal that Ni doping of perovskites causes an increase of defect formation energy and does not introduce deep trap states in the band gap, which is suggested to be the main reason for the improved local structural order and near-unity PLQY. Our ability to obtain violet-emitting perovskite NCs with near-perfect properties opens the door for a range of applications in violet-emitting perovskite-based devices such as light-emitting diodes, single-photon sources, lasers, and beyond