Pyridine-containing metal-organic frameworks as precursor for nitrogen-doped porous carbons with high-performance capacitive behavior

Hierarchically activated porous carbon derived from zinc-based fluorine containing metal-organic framework as extremely high specific capacitance and rate performance electrode material for advanced supercapacitors

In this work, a hierarchically activated porous carbon (APC) was synthesized using fluorine-containing metal-organic framework via facile combined carbonization and KOH activation treatments. The influences of activation conditions on the surface structures and electrochemical performance of APC were systematically studied. Afterwards, the electrochemical responses of APC electrode were further assessed from the cyclic voltammetry and galvanostatic charge-discharge examinations by 6 M KOH electrolyte. The as-obtained APC electrode delivered the high specific capacitances of 540.8 and 280 F g^-1 at 1 and 500 A g^-1, correspondingly with superior capacitance retention of 94% after 250,000 cycles even at 100 A g^-1, which is showing that its outstanding capacitance, remarkable rate capacity, and very-long cyclic life. Furthermore, the as-assembled APC-based symmetrical supercapacitor offers a superb energy density of 19 Wh kg^-1 at 182 W kg^-1, indicating its large-scale application. Thus, this work proposes a potential route to synthesize highly efficient porous carbon material for the future development of energy storage systems.

Porous Carbon-Based Supercapacitors Directly Derived from Metal-Organic Frameworks

Numerously different porous carbons have been prepared and used in a wide range of practical applications. Porous carbons are also ideal electrode materials for efficient energy storage devices due to their large surface areas, capacious pore spaces, and superior chemical stability compared to other porous materials. Not only the electrical double-layer capacitance (EDLC)-based charge storage but also the pseudocapacitance driven by various dopants in the carbon matrix plays a significant role in enhancing the electrochemical supercapacitive performance of porous carbons. Since the electrochemical capacitive activities are primarily based on EDLC and further enhanced by pseudocapacitance, high-surface carbons are desirable for these applications. The porosity of carbons plays a crucial role in enhancing the performance as well. We have recently witnessed that metal-organic frameworks (MOFs) could be very effective self-sacrificing templates, or precursors, for new high-surface carbons for supercapacitors, or ultracapacitors. Many MOFs can be self-sacrificing precursors for carbonaceous porous materials in a simple yet effective direct carbonization to produce porous carbons. The constituent metal ions can be either completely removed during the carbonization or transformed into valuable redox-active centers for additional faradaic reactions to enhance the electrochemical performance of carbon electrodes. Some heteroatoms of the bridging ligands and solvate molecules can be easily incorporated into carbon matrices to generate heteroatom-doped carbons with pseudocapacitive behavior and good surface wettability. We categorized these MOF-derived porous carbons into three main types: (i) pure and heteroatom-doped carbons, (ii) metallic nanoparticle-containing carbons, and (iii) carbon-based composites with other carbon-based materials or redox-active metal species. Based on these cases summarized in this review, new MOF-derived porous carbons with much enhanced capacitive performance and stability will be envisioned.

From metal-organic frameworks to porous carbon materials: recent progress and prospects from energy and environmental perspectives

Metal-organic frameworks (MOFs) have emerged as promising materials in the areas of gas storage, magnetism, luminescence, and catalysis owing to their superior property of having highly crystalline structures. However, MOF stability toward heat or humidity is considerably less as compared to carbons because they are constructed from the assembly of ligands with metal ions or clusters via coordination bonds. Transforming MOFs into carbons is bringing the novel potential for MOFs to achieve industrialization, and carbons with controlled pore sizes and surface doping are one of the most important porous materials. By selecting MOFs as a precursor or template, carbons with heteroatom doping and well-developed pores can be achieved. In this review, we discussed the state-of-art study progress made in the new development of MOF-derived metal-free porous carbons. In particular, the potential use of metal-free carbons from environmental and energy perspectives, such as adsorption, supercapacitors, and catalysts, were analyzed in detail. Moreover, an outlook for the sustainable development of MOF-derived porous carbons in the future was also presented.

New and Advanced Porous Carbon Materials in Fine Chemical Synthesis. Emerging Precursors of Porous Carbons

The efficiency of porous carbons in fine chemical synthesis, among other application fields, has been demonstrated since both the porous structure and chemical surface provide the appropriated chemical environment favoring a great variety of relevant chemical transformations. In recent years, metal organic frameworks (MOFs) and covalent organic frameworks (COFs) have emerged as interesting opportunities in the preparation of porous carbons with improved physico-chemical properties. Direct calcination of MOFs or COFs, in the presence or not of others carbon or heteroatom sources, could be considered an easy and practical approach for the synthesis of highly dispersed heteroatom-doped porous carbons but also new porous carbons in which single atoms of metallic species are present, showing a great development of the porosity; both characteristics of supreme importance for catalytic applications. The goal of this review is to provide an overview of the traditional methodologies for the synthesis of new porous carbon structures together with emerging ones that use MOFs or COFs as carbon precursors. As mentioned below, the catalytic application in fine chemical synthesis of these kinds of materials is at present barely explored, but probably will expand in the near future.

Poly(vinylidene fluoride) and Carbon Derivative Structures from Eco-Friendly MOF-5 for Supercapacitor Electrode Preparation with Improved Electrochemical Performance

Electrodes from carbonized Zn₄O(1,4-benzodicarboxylic acid) (MOF-5) structures were prepared successfully via evaporating the solvent with a poly(vinylidene fluoride) (PVDF) binder. The solvent used for a nanocomposite cast was easily removed. Such an elegant method for preparing electrodes provides a facile, cost-effective, and void/cracking-free nanocomposite distribution on the current collector. The highly porous nanoparticles containing pure carbon attach well to the PVDF membrane which results in an increased active surface area of the electrode to 847 m²/g. The electrochemical analysis shows that the best weight ratio of CMOF-5 to PVDF equals 85:15, 80:20, and 75:25, respectively. The specific capacitance of these samples is 218 F/g, 210 F/g, and 180 F/g, correspondingly. An additional advantage of the electrode prepared from the carbonized MOF-5 is the possibility to synthesis MOF structures from recovered substrates used in its synthesis (distilled N,N-Dimethylformamide DMF and terephthalic acid recovered from polyethylene terephthalate waste). We will demonstrate this in this contribution as well. Furthermore, the carbonized MOF-5 can be recovered from the spent electrode and reused again in the electrochemical device.