The shuttling of polysulfides on the cathode and the uncontrollable growth of lithium dendrites on the anode have restricted the practical application of lithium-sulfur (Li-S) batteries. In this study, a metal-coordinated 3D covalent organic framework (COF) with a homogeneous distribution of nickel-bis(dithiolene) and N-rich triazine centers (namely, NiS4-TAPT) was designed and synthesized, which can serve as bifunctional hosts for both sulfur cathodes and lithium anodes in Li-S batteries. The abundant Ni centers and N-sites in NiS4-TAPT can greatly enhance the adsorption and conversion of the polysulfides. Meanwhile, the presence of Ni-bis(dithiolene) centers enables uniform Li nucleation at the Li anode, thereby suppressing the growth of Li dendrites. This work demonstrated the effectiveness of integrating catalytic and adsorption sites to optimize the chemical interactions between host materials and redox-active intermediates, potentially facilitating the rational design of metal-coordinated COF materials for high-performance secondary batteries.
Redox-active tetrathiafulvalene (TTF)-based covalent organic frameworks (COFs) exhibit distinctive electrochemical and photoelectrical properties, but their prevalent two-dimensional (2D) structure with densely packed TTF moieties limits the accessibility of redox center and constrains their potential applications. To overcome this challenge, an 8-connected TTF linker (TTF-8CHO) is designed as a new building block for the construction of three-dimensional (3D) COFs. This approach led to the successful synthesis of a 3D COF with the bcu topology, designated as TTF-8CHO-COF. In comparison to its 2D counterpart employing a 4-connected TTF linker, the 3D COF design enhances access to redox sites, facilitating controlled oxidation by I2 or Au3+ to tune physical properties. When irradiated with a 0.7 W cm-2 808 nm laser, the oxidized 3D COF samples ( I X - ${\mathrm{I}}_{\mathrm{X}}^{-}$ @TTF-8CHO-COF and Au NPs@TTF-8CHO-COF) demonstrated rapid temperature increases of 239.3 and 146.1 °C, respectively, which surpassed those of pristine 3D COF (65.6 °C) and the 2D COF counterpart (6.4 °C increment after I2 treatment). Furthermore, the oxidation of the 3D COF heightened its photoelectrical responsiveness under 808 nm laser irradiation. This augmentation in photothermal and photoelectrical response can be attributed to the higher concentration of TTF·+ radicals generated through the oxidation of well-exposed TTF moieties.
Combining the chemistry of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) can bring new opportunities for the design of advanced materials with enhanced tunability and functionality. Herein, we constructed two COFs based on Ni-bis(dithiolene) units and imine bonds, representing a bridge between traditional MOFs and COFs. The Ni-bis(dithiolene)tetrabenzaldehyde as the 4-connected linker was initially synthesized, which was further linked by 4-connected tetra(aminophenyl)pyrene (TAP) or 3-connected tris(aminophenyl)amine (TAA) linkers into two COFs, namely, Ni-TAP and Ni-TAA. Ni-TAP shows a two-dimensional sql network, while TAA is a twofold interpenetrated framework with an ffc topology. They both exhibit a high Brunauer-Emmett-Teller surface area (324 and 689 m2 g-1 for Ni-TAP and Ni-TAA, respectively), a fairly good conductivity (1.57 × 10-6 and 9.75 × 10-5 S m-1 for Ni-TAP and Ni-TAA, respectively), and high chemical stability (a stable pH window of 1-14 for Ni-TAA). When applied in lithium metal batteries as an intermediate layer for guiding the uniform Li electrodeposition, Ni-TAP and Ni-TAA displayed impressive lithiophilicity and high Li-ion conductivity, enabling the achievement of smooth and dense Li deposition with a clear columnar morphology and stable Li plating/stripping behaviors with high Li utilization, which is anticipated to pave the way to upgrade Li metal anodes for application in high-energy-density battery systems.
Comprised of a battery anode and a supercapacitor cathode, hybrid lithium-ion capacitors (HLICs) are found to be an effective solution to realize both high power density and high energy density at the same time. Organic-inorganic hybrid materials with well-organized framework guided by the reticular chemistry are one of the promising anode materials for HLICs because of rich active sites and ordered porosity. Herein, metal-organic framework consisting of Zr4+ metal ions and tetrathiafulvalene-based ligands (Zr-MOF) is proposed as the pseudocapacitive anode of HLICs. The Zr-MOF possesses high stability, high crystallinity, and multiple meso-microporous channels favorable for ion transport. The as-prepared Zr-MOF||activated carbon HLICs present high energy density (122.5 Wh kg-1 ), high power density (12.5 kW kg-1 ), and stable cycling performance (86% capacity retention after 1000 cycles at 2000 mA g-1 ) within the operating voltage range of 1.0-4.0 V. The results expand the direct application of MOF for bridging the performance gap between batteries and supercapacitors.
The antibiotic resistance induced by the release of antibiotics to the environment has urged research towards developing effective technologies for antibiotic removal from wastewater. Traditional technologies such as activated sludge processes are not effective for antibiotic removal. Recently, microalgae-based technology has been explored as a potential alternative for the treatment of wastewater containing antibiotics by adsorption, accumulation, biodegradation, photodegradation, and hydrolysis. In this review, the toxicities of antibiotics on microalgae, the mechanisms of antibiotic removal by microalgae, and the integration of microalgae with other technologies such as ultraviolet irradiation (photocatalysis), advanced oxidation, and complementary microorganism degradation for antibiotic removal were discussed. The limitations of current microalgae-based technology and future research needs were also discussed.
Anti-Bacterial Agents/analysis , Anti-Bacterial Agents/toxicity , Microalgae/drug effects , Microalgae/metabolism , Waste Disposal, Fluid/methods , Wastewater/chemistry , Adsorption , Biodegradation, Environmental , Drug Resistance, Microbial/physiology , Hydrolysis , Photolysis , Sewage/chemistry , Ultraviolet Rays
In this study, we have reported nitrogen-doped graphite C coated Co nanocomposite (Co@CN) catalysts synthesized by one-step arc discharge method. The surface compositions, morphologies and the catalytic properties of the Co@CN nanocomposites were studied minutely. The results reveal that the prepared Co@CN nanocomposites have typical core-shell structure and show highly efficient catalytic performance in a reduction of 4-nitrophenol (4-NP), rhodamine and methylene blue. Their rate constant (Kapp) is 0.074 s-1 in a reduction of 4-NP, which is much higher than that of reported transition metal-based catalysts. Moreover, the overpotential of Co@CN is only 96 mV at a current density of 10 mA cm-2 in alkaline solution, showing high electrocatalytic activities in the hydrogen evolution reaction. The excellent synergistic effect between nitrogen-doped graphite C shell and magnetic Co core enables the Co@CN nanocomposites catalysts to hold abundant active sites and to transmit rapidly electron ability, resulting in Co@CN nanocomposite catalysts having a highly efficient catalytic nature.
