Metal-Organic Framework with Aromatic Rings Tentacles: High Sulfur Storage in Li-S Batteries and Efficient Benzene Homologues Distinction

Visible-Light Photocatalytic Activity of a ZnO-Loaded Isoreticular Metal-Organic Framework

A hybrid material composed of IRMOF-3 and ZnO (IRMOF-3/ZnO) was synthesized to enhance photocatalytic methylene blue (MB) degradation under visible-light irradiation. Scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and diffuse-reflectance UV-Vis analyses confirmed the successful integration of ZnO into the IRMOF-3 framework. Compared with unmodified IRMOF-3, the hybrid demonstrated superior MB decomposition, as evidenced by faster reaction rate constants and shorter half-lives. Monitoring the MB absorbance at 670 nm (λmax) revealed more pronounced colorant removal when IRMOF-3/ZnO was exposed to a visible-light source. Diffuse-reflectance UV-Vis spectroscopy showed that IRMOF-3 has a band gap of 2.7 eV, whereas IRMOF-3/ZnO exhibits a slightly higher band gap of 2.8 eV. This modest shift, coupled with the strong interaction between the ZnO semiconductor and the MOF's amine functionalities, enabled two distinct energy-transfer pathways: intermolecular transfer from IRMOF-3 linkers (acting as visible-light antennas) to ZnO, and intramolecular transfer from Zn to IRMOF-3. Together, these pathways generated abundant free radicals for efficient dye degradation. Despite the necessity for careful synthesis protocols and control of operating conditions to preserve the MOF structure and optimize ZnO loading, the IRMOF-3/ZnO hybrid shows promise as a robust, cost-effective photocatalyst for water-pollutant remediation, taking advantage of the more abundant visible region of solar light.

Advanced Polymers in Cathodes and Electrolytes for Lithium-Sulfur Batteries: Progress and Prospects

Lithium-sulfur (Li-S) batteries, which store energy through reversible redox reactions with multiple electron transfers, are seen as one of the promising energy storage systems of the future due to their outstanding advantages. However, the shuttle effect, volume expansion, low conductivity of sulfur cathodes, and uncontrollable dendrite phenomenon of the lithium anodes have hindered the further application of Li-S batteries. In order to solve the problems and clarify the electrochemical reaction mechanism, various types of materials, such as metal compounds and carbon materials, are used in Li-S batteries. Polymers, as a class of inexpensive, lightweight, and electrochemically stable materials, enable the construction of low-cost, high-specific capacity Li-S batteries. Moreover, polymers can be multifunctionalized by obtaining rich structures through molecular design, allowing them to be applied not only in cathodes, but also in binders and solid-state electrolytes to optimize electrochemical performance from multiple perspectives. The most widely used areas related to polymer applications in Li-S batteries, including cathodes and electrolytes, are selected for a comprehensive overview, and the relevant mechanisms of polymer action in different components are discussed. Finally, the prospects for the practical application of polymers in Li-S batteries are presented in terms of advanced characterization and mechanistic analysis.

Construction of a Cu-Based Metal-Organic Framework by Employing a Mixed-Ligand Strategy and Its Facile Conversion into Nanofibrous CuO for Electrochemical Energy Storage Applications

Recently, metal-organic frameworks (MOFs) have been widely employed as a sacrificial template for the construction of nanostructured materials for a range of applications including energy storage. Herein, we report a facile mixed-ligand strategy for the synthesis of a Cu-MOF, [Cu₃(Azopy)₃(BTTC)₃(H₂O)₃·2H₂O]_n (where BTTC = 1,2,4,5-benzenetetracarboxylic acid and Azopy = 4,4'-azopyridine), via a slow-diffusion method at room temperature. X-ray analysis authenticates the two-dimensional (2D)-layered framework of Cu-MOF. Topologically, this 2D-layered structure is assigned as a 4-connected unimodal net with sql topology. Further, nanostructured CuO is obtained via a simple precipitation method by employing Cu-MOF as a precursor. After analysis of their physicochemical properties through various techniques, both materials are used as surface modifiers of glassy carbon electrodes for a comparative electrochemical study. The results reveal a superior charge storage performance of CuO (244.2 F g^-1 at a current density of 0.8 A g^-1) with a high rate capability compared to Cu-MOF. This observation paves the pathway for the strategic design of high-performing supercapacitor electrode materials.

Porous Metal-Organic Frameworks Containing Reversible Disulfide Linkages as Cathode Materials for Lithium-Ion Batteries

Three porous disulfide-ligand-containing metal-organic frameworks (DS-MOFs) and two nonporous coordination polymers with disulfide ligands (DS-CPs) with various structural dimensionalities were used as cathode active materials in lithium batteries. Charge/discharge performance examinations revealed that only porous DS-MOF-based batteries exhibited significant capacities close to the theoretical values, which was ascribed to the insertion of electrolyte ions into the DS-MOFs. The insolubility of porous 3 D DS-MOFs in the electrolyte resulted in cycling performances superior to that of their 1 D and 2 D porous counterparts. Battery reactions were probed by instrumental analyses. The dual redox reactions of metal ions and disulfide ligands in the MOFs resulted in higher capacities, and the presence of reversible electrochemically dynamic S-S bonds stabilized the cycling performance. Thus, the strategy of S-S moiety trapping in MOFs and the obtained correlation between the structural features and battery performance could contribute to the design of high-performance MOF-based batteries and the practical realization of Li-S batteries.

MIL-88A Metal-Organic Framework as a Stable Sulfur-host Cathode for Long-cycle Li-S Batteries

Lithium-sulfur (Li-S) batteries have received enormous interest as a promising energy storage system to compete against limited, non-renewable, energy sources due to their high energy density, sustainability, and low cost. Among the main challenges of this technology, researchers are concentrating on reducing the well-known “shuttle effect” that generates the loss and corrosion of the active material during cycling. To tackle this issue, metal-organic frameworks (MOF) are considered excellent sulfur host materials to be part of the cathode in Li-S batteries, showing efficient confinement of undesirable polysulfides. In this study, MIL-88A, based on iron fumarate, was synthesised by a simple and fast ultrasonic-assisted probe method. Techniques such as X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and N₂ adsorption/desorption isotherms were used to characterise structural, morphological, and textural properties. The synthesis process led to MIL-88A particles with a central prismatic portion and pyramidal terminal portions, which exhibited a dual micro-mesoporous MOF system. The composite MIL-88A@S was prepared, by a typical melt-diffusion method at 155 °C, as a cathodic material for Li-S cells. MIL-88A@S electrodes were tested under several rates, exhibiting stable specific capacity values above 400 mAh g⁻¹ at 0.1 C (1C = 1675 mA g⁻¹). This polyhedral and porous MIL-88A was found to be an effective cathode material for long cycling in Li-S cells, retaining a reversible capacity above 300 mAh g⁻¹ at 0.5 C for more than 1000 cycles, and exhibiting excellent coulombic efficiency.

Thermal Modulation of MOF and Its Application in Lithium-Sulfur Batteries

The applications of metal-organic frameworks (MOFs) as sulfur hosts focus on pristine MOFs and their carbonization products for establishing high-performance lithium-sulfur batteries (LSBs). However, the mechanism that modulates the specific nanostructures and the compositions at different treatment temperatures still needs further exploration. In this work, we modulate the pyrolysis products of UiO-66-NH₂@rGO (U@rGO) at a predetermined specific temperature by thermogravimetric (TG) analysis and systematically investigate their microstructure and chemical characteristic evolution. The composite processed at 300 °C (U@rGO-P300) results in the rearrangement of an octahedral nanophase into an amorphous material while retaining a large number of functional groups of -NH₂ and COO-, which lead to an additional nanostructure interface and a high Brunauer-Emmett-Teller (BET) surface area of 298.4 m² g^-1. Moreover, the newly created abundant suboxidative Zr³⁺ atom sites serve as the polysulfide anchor and transfer mediator active sites. The assembled LSBs could deliver a capacity of 906.1 and retain 801.7 mA h g^-1 after 300 cycles at 1C with a low fading rate of around 0.05% per cycle and an improved rate performance of 619.1 mA h g^-1 at 4C. The Li⁺ diffusion coefficients are significantly increased by 10-60 times. This work provides a simple route to activate the metal sites in the MOF category with a suboxidative state, leading to intriguing and unanticipated properties.

Effect of Varying the Ratio of Carbon Black to Vapor-Grown Carbon Fibers in the Separator on the Performance of Li⁻S Batteries

Lithium–sulfur (Li–S) batteries are expected to be very useful for next-generation transportation and grid storage because of their high energy density and low cost. However, their low active material utilization and poor cycle life limit their practical application. The use of a carbon-coated separator in these batteries serves to inhibit the migration of the lithium polysulfide intermediate and increases the recyclability. We report the extent to which the electrochemical performance of Li–S battery systems depends on the characteristics of the carbon coating of the separator. Carbon-coated separators containing different ratios of carbon black (Super-P) and vapor-grown carbon fibers (VGCFs) were prepared and evaluated in Li–S batteries. The results showed that larger amounts of Super-P on the carbon-coated separator enhanced the electrochemical performance of Li–S batteries; for instance, the pure Super-P coating exhibited the highest discharge capacity (602.1 mAh g⁻¹ at 150 cycles) with a Coulombic efficiency exceeding 95%. Furthermore, the separators with the pure Super-P coating had a smaller pore structure, and hence, limited polysulfide migration, compared to separators containing Super-P/VGCF mixtures. These results indicate that it is necessary to control the porosity of the porous membrane to control the movement of the lithium polysulfide.

Highly Sensitive and Discriminative Detection of BTEX in the Vapor Phase: A Film-Based Fluorescent Approach

BTEX (benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene) represents a group of volatile organic compounds (VOCs) and constitutes a great threat to human health. However, sensitive, selective, and speedy detection of them on-site and in the vapor phase remains a challenge for years. Herein, we report a film-based fluorescent approach and a conceptual sensor, which shows unprecedented sensitivity, speed, and reversibility to the aromatic hydrocarbons in the vapor phase. In the studies, pentiptycene was employed to produce a nonplanar perylene bisimide (PBI) derivative, P-PBI. The compound was further utilized to fabricate the film. The novelty of the design is the combination of capillary condensation and solvent effect, which is expected to enrich the analytes from vapor phase and shows outputs at the same time. Importantly, the film permits instant response (∼3 s) and real-time identification (<1 min) of benzene and toluene from other aromatic hydrocarbons. The experimental detection limits (DLs) of the six analytes are lower than 9.2, 2.7, 1.9, 0.2, 0.4, and 0.4 ppm, which with the exception of benzene, are significantly lower than the NIOSH recommended long-term exposure limits. More importantly, the film is photochemically stable, and more than 300 repetitive tests showed no observable bleaching. In addition, the sensing is fully reversible. The superior performance of the film device is in support of the assumption that the combination of capillary condensation and solvation effect would constitute an effective way to design high-performance fluorescent films, especially for challenging chemical inert and photoelectronically inactive VOCs.

Pristine Metal-Organic Frameworks and their Composites for Energy Storage and Conversion

Metal-organic frameworks (MOFs), a new class of crystalline porous organic-inorganic hybrid materials, have recently attracted increasing interest in the field of energy storage and conversion. Herein, recent progress of MOFs and MOF composites for energy storage and conversion applications, including photochemical and electrochemical fuel production (hydrogen production and CO₂ reduction), water oxidation, supercapacitors, and Li-based batteries (Li-ion, Li-S, and Li-O₂ batteries), is summarized. Typical development strategies (e.g., incorporation of active components, design of smart morphologies, and judicious selection of organic linkers and metal nodes) of MOFs and MOF composites for particular energy storage and conversion applications are highlighted. A broad overview of recent progress is provided, which will hopefully promote the future development of MOFs and MOF composites for advanced energy storage and conversion applications.

Metal-Embedded Porous Graphitic Carbon Fibers Fabricated from Bamboo Sticks as a Novel Cathode for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are deemed to be among the most prospective next-generation advanced high-energy batteries. Advanced cathode materials fabricated from biological carbon are becoming more popular due to their unique properties. Inspired by the fibrous structure of bamboo, herein we put forward a smart strategy to convert bamboo sticks for barbecue into uniform bamboo carbon fibers (BCF) via a simple hydrothermal treatment proceeded in alkaline solution. Then NiCl₂ is used to etch the fibers through a heat treatment to achieve Ni-embedded porous graphitic carbon fibers (PGCF/Ni) for LSBs. The designed PGCF/Ni/S electrode exhibits improved electrochemical performances including high initial capacity (1198 mAh g^-1 at 0.2 C), prolonged cycling life (1030 mAh g^-1 at 0.2 C after 200 cycles), and improved rate capability. The excellent properties are attributed to the synergistic effect of 3D porous graphitic carbon fibers with highly conductive Ni nanoparticles embedded.