Morphology control of nanoscale metal-organic frameworks for high-performance supercapacitors

Hierarchical 2D/1D MOFs/electrospun ZIF-67 modified carbon nanofibers heterostructure electrode for high-performance asymmetric supercapacitor

In this paper, a 2 dimensional (2D) metal-organic frameworks (MOFs) nanosheets grown on 1D ZIF-67 modified carbon nanofibers (CNFs) was designed and fabricated with a hierarchical heterostructure. The hierarchical 2D/1D MOFs/CCNF offers rich electrochemical active sites and favorable ion/electron diffusion pathways. The synergistic effect of Co, CNFs and MOFs from heterostructures contributes to superb electrochemical activities. Benefiting from the hierarchical heterostructures optimized by the mass ratio of ZIF-67/PAN and CCNF/NiMOF as well as the type of substrates, CCNF-20@MOF showed a specific capacity of 361.50 C g-1 at 0.5 A g-1, whose charge storage mechanism is dominated by diffusion control. Meanwhile, a bamboo-derived carbon material (BBC) was designed in the solid-state asymmetric supercapacitor (CCNF-20@MOF//BBC). The device exhibited an energy density of 38.89 Wh kg-1 at the power density of 800.02 W kg-1 and excellent cycling stability, that exceed many MOFs based devices. Moreover, it could be successfully used for LED light-emitting, demonstrating a good application prospect. This work provides a feasible strategy for the improved performance of MOFs and CNFs based materials in the field of energy storage.

Size-dependent photocatalytic inactivation of Microcystis aeruginosa and degradation of microcystin by a copper metal organic framework

Water eutrophication has led to increasingly serious algal blooms (HABs) that pose significant threats to aquatic environmental and human health. Differently sized copper metal organic frameworks (Cu-MOFs), including Cu-MOF-1 (30 nm), Cu-MOF-2, (40 nm), Cu-MOF-3 (50 nm), and Cu-MOF-4 (1 µm×100 nm), were synthesized. Their performance in inactivating Microcystis aeruginosa and degrading microcystin was assessed at the concentration of 0-60 mg/L under visible light irradiation for 6 h. The photocatalytic antialgal activity of Cu-MOF-4 was 10.5%, 14.2%, and 31.2% higher than that of Cu-MOF-3, Cu-MOF-2, and Cu-MOF-1; the efficacy in photocatalytic degradation of microcystin induced by Cu-MOFs also exhibited significant size-dependent efficiency, where Cu-MOF-4 was 2.6-, 1.8-, and 2.0-fold of Cu-MOF-3, Cu-MOF-2, and Cu-MOF-1, respectively. Cu-MOF-4 had greater performance than other Cu-MOFs could attributed to: 1) Cu-MOF-4 is easier to interact with algal cells due to its lower surface negative charge and higher hydrophobicity, resulting in more photocatalyst-algae heteroaggregates formation; 2) Cu-MOF-4 had greater electron-hole pairs separation ability, thus exhibiting higher reactive oxygen species (ROS) production; 3) Cu-MOF-4 had greater hydrostability than other Cu-MOFs, leading to more sustained ROS generation. Additionally, the reusability of Cu-MOF-4 was also greater than other Cu-MOFs.

Advances of Electroactive Metal-Organic Frameworks

The preparation of electroactive metal-organic frameworks (MOFs) for applications of supercapacitors and batteries has received much attention and remarkable progress during the past few years. MOF-based materials including pristine MOFs, hybrid MOFs or MOF composites, and MOF derivatives are well designed by a combination of organic linkers (e.g., carboxylic acids, conjugated aromatic phenols/thiols, conjugated aromatic amines, and N-heterocyclic donors) and metal salts to construct predictable structures with appropriate properties. This review will focus on construction strategies of pristine MOFs and hybrid MOFs as anodes, cathodes, separators, and electrolytes in supercapacitors and batteries. Descriptions and discussions follow categories of electrochemical double-layer capacitors (EDLCs), pseudocapacitors (PSCs), and hybrid supercapacitors (HSCs) for supercapacitors. In contrast, Li-ion batteries (LIBs), Lithium-sulfur batteries (LSBs), Lithium-oxygen batteries (LOBs), Sodium-ion batteries (SIBs), Sodium-sulfur batteries (SSBs), Zinc-ion batteries (ZIBs), Zinc-air batteries (ZABs), Aluminum-sulfur batteries (ASBs), and others (e.g., LiSe, NiZn, H⁺ , alkaline, organic, and redox flow batteries) are categorized for batteries.

Enhancing the energy storage performances of metal-organic frameworks by controlling microstructure

Metal-organic frameworks (MOFs) are among the most promising materials for next-generation energy storage systems. However, the impact of particle morphology on the energy storage performances of these frameworks is poorly understood. To address this, here we use coordination modulation to synthesise three samples of the conductive MOF Cu₃(HHTP)₂ (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with distinct microstructures. Supercapacitors assembled with these samples conclusively demonstrate that sample microstructure and particle morphology have a significant impact on the energy storage performances of MOFs. Samples with 'flake-like' particles, with a pore network comprised of many short pores, display superior capacitive performances than samples with either 'rod-like' or strongly agglomerated particles. The results of this study provide a target microstructure for conductive MOFs for energy storage applications.

Reticular Nanoscience: Bottom-Up Assembly Nanotechnology

The chemistry of metal-organic and covalent organic frameworks (MOFs and COFs) is perhaps the most diverse and inclusive among the chemical sciences, and yet it can be radically expanded by blending it with nanotechnology. The result is reticular nanoscience, an area of reticular chemistry that has an immense potential in virtually any technological field. In this perspective, we explore the extension of such an interdisciplinary reach by surveying the explored and unexplored possibilities that framework nanoparticles can offer. We localize these unique nanosized reticular materials at the juncture between the molecular and the macroscopic worlds, and describe the resulting synthetic and analytical chemistry, which is fundamentally different from conventional frameworks. Such differences are mirrored in the properties that reticular nanoparticles exhibit, which we described while referring to the present state-of-the-art and future promising applications in medicine, catalysis, energy-related applications, and sensors. Finally, the bottom-up approach of reticular nanoscience, inspired by nature, is brought to its full extension by introducing the concept of augmented reticular chemistry. Its approach departs from a single-particle scale to reach higher mesoscopic and even macroscopic dimensions, where framework nanoparticles become building units themselves and the resulting supermaterials approach new levels of sophistication of structures and properties.

CNTs support 2D NiMOF nanosheets for asymmetric supercapacitors with high energy density

The NiMOF/CNTs composite with NiMOF nanosheets grows along the CNTs is synthesized with a one-step solvothermal method, and the NiMOF/CNTs//AC asymmetric supercapacitors provide a high energy density of 113.8 Wh kg−1 at 800.0 W kg−1.

State of the art developments and prospects of metal-organic frameworks for energy applications

The progress on technologies for the cleaner and ecological transformation and storage of energy to combat effluence or pollution and the impending energy dilemma has recently attracted interest from energy research groups, particularly in the field of coordination chemistry, among inorganic chemists. Carriers for storing energy or facilitating mass and e^- transport are considered significant for energy conversion. Accordingly, considering their properties such as large surface area, low cost, customizable pore diameter, tunable topologies, low densities, and variable frameworks, MOFs (metal-organic frameworks) and their derivatives are well-suited for this purpose. MOFs are an innovative category of porous and crystalline materials, which have gained significant interest in recent years. Thus, herein, we highlight the state of the art progress on MOFs for energy-based applications, as perfect compounds and elements in compound assemblies for converting solar energy, lithium-ion arrays, fuel devices, hydrogen production, photocatalytic CO₂ reduction, proton conduction, etc. In addition, the substantial progress achieved in the production of various composites and derivatives containing MOFs with particular focus on supercapacitors and gas adsorption and storage is summarized, concentrating on the correlation between their coordination structural frameworks and applications in the field of energy. The current improved strategies, challenges, and future prospects are also presented in view of the coordination chemistry governing the structural modification of MOFs for energy applications.

The Application of Metal-Organic Frameworks and Their Derivatives for Supercapacitors

Supercapacitors (SCs), one of the most popular types of energy-storage devices, present lots of advantages, such as large power density and fast charge/discharge capability. Being the promising SCs electrode materials, metal-organic frameworks (MOFs) and their derivatives have gained ever-increasing attention due to their large specific surface area, controllable porous structure and rich diversity. Herein, the recent development of MOFs-based materials and their application in SCs as the electrode are reviewed and summarized. The preparation method, the morphology of the materials and the electrical performance of various MOFs and their derivatives (such as carbon, metal oxide/hydroxide and metal sulfide) are briefly discussed. Most of recent works concentrate on Ni-, Co- and Mn-MOFs and their composites/derivatives. Conclusions and our outlook for the researches are also given, which would be a valuable guideline for the rational design of MOFs materials for SCs in the near future.