Electrochemical energy storage devices provide a promising method for storing electrical energy from renewable but intermittent energy sources such as wind, sunlight, biofuels, hydroelectric power, and geothermal energy.

Currently, carbon-containing materials have attracted wide interest due to their wide applications, including adsorption, catalysis, batteries, fuel cells, supercapacitors, and drug delivery and imaging. In addition, some sensors are also one of the important applications of carbonaceous materials because they are closely related to human health.

There are various methods for preparing carbon materials, such as direct carbonization from organic precursors, physical or chemical carbonization from carbon, template methods using zeolite and mesoporous silica, high-temperature solvothermal and hydrothermal methods, arc methods and chemical methods . Vapor phase decomposition (CVD) method.

Among all these methods, due to the flexibility and simplicity of organic precursors, carbonization directly from organic precursors is the most common method for preparing nanoporous carbon. However, these materials have certain disadvantages, such as low surface area, chaotic structure and uneven size, which will greatly limit their application.

However, researchers have found that carbon materials derived from metal organic frameworks (MOF) can overcome these limitations (please read our primer on metal organic frameworks ).

MOF is an organic-inorganic hybrid crystalline porous material composed of single metal ions or metal clusters connected by multifunctional organic ligands. Compared with other porous materials, MOF provides unique structural diversity, which can successfully control the framework topology, porosity and function.

Carbon materials derived from MOF have various advantages derived from their MOF, such as high porosity (up to 90%), extremely high surface area (nearly 10,000 m 2 g -1 ), adjustable pore size and excellent cycle life.

As a result, MOF-derived carbon materials have shown encouraging applications, including adsorption, energy storage and conversion, gas storage and separation, catalysis, chemical sensing, and solid phase extraction.

Published in the " Advanced Materials" ( "metal - organic frameworks derived carbon material application " ) in a review article summarizes the application of MOF-derived carbon material.

The author is committed to the application of batteries, supercapacitors, electrocatalytic reactions (including oxygen reduction reactions, oxygen evolution reactions and hydrogen evolution reactions) and water treatment.

MOF-derived carbon materials and their promising applications. (Reprinted with permission from Wiley-VCH Verlag) (click on the image to enlarge)

Metal-organic framework-derived carbon materials for batteries

In order to improve the electrochemical activity of the battery, the researchers also designed and studied carbon materials derived from MOF. Since controlling the morphology of the electrode materials during the manufacturing process is important to the battery‘s chemical properties, this review lists the applications of these applications in different types of batteries (lithium ion batteries, lithium sulfur batteries, sodium ion batteries, etc.). According to the shape of the carbonaceous material in the electrode, choose a variety of batteries (such as lithium-selenium batteries).

This section discusses in detail the various carbon materials being developed for batteries: ordinary porous carbon; carbon nanosheets; carbon nanocages and other morphologies, such as cuboids and nanorods.

When reviewing the literature, the authors concluded that by controlling the carbonization temperature, adjusting various forms and changing the reaction conditions, a large amount of MOF-derived carbon materials have been applied to batteries.

Super capacitor carbon material derived from metal-organic framework

Electrochemical capacitors, also known as supercapacitors, are electrochemical energy storage devices that provide higher power density than batteries and higher energy density than traditional dielectric capacitors.

Supercapacitors have the huge advantage of fast charging and discharging and extremely long cycle life. However, their energy density may be lower compared to batteries. When different types of electrodes are used, supercapacitors may be more complex devices because composite electrodes can perform capacitive and Faraday charge storage.

This section summarizes some typical supercapacitors, which are classified according to their electrode materials: nanoporous carbon; metal oxide / carbon composite materials; and other nanocomposite materials.

Carbon materials derived from metal-organic frameworks for electrocatalytic reactions

Although great progress has been made in the design and application of MOF-based materials, until recently, their potential applications in the field of electrochemical catalysis have attracted researchers‘ attention.

Fuel cells, especially H 2 / O 2 or H 2 / air batteries, have become promising candidates for providing energy to vehicles and converting H 2 (together with O 2 or air) into intermittent renewable resources ( Such as sunlight, wind and waves).

OER is an anode reaction in which H is the core of step 2 in the oxidation of O solvent to O 2 , and ORR the main reaction at the cathode reaction, may be formed as O 2 generating H is reduced to 2 ö 2 2 via the - electronic means, or H 2 o passes through a 4 - electron pathway.

The review focuses on the application of MOF-based materials as catalysts in these important energy conversion electrochemical reactions, including oxygen reduction reactions, oxygen release reactions, and hydrogen release reactions.

Metal-organic framework-derived carbon materials for water treatment

Many efforts have been made to reduce and / or remove environmental pollutants, and many environmental pollution treatment technologies have emerged, such as biological treatment, chemical oxidation, adsorption, and membrane separation methods.

Among them, the adsorption method has been favored. The advantages of high specific surface area, high porosity and adjustable porosity, structural diversity, open metal sites and chemical modification make MOF-derived carbon materials (especially ZIF-8 derived porous carbon) into application Excellent material. Adsorption as they increase the active site.

Finally, the author summarizes some of the main challenges in this area:

1) The preparation route of most MOF-derived carbon materials depends on high-temperature calcination. However, calcination usually destroys the ordered structure and porous morphology of MOF, and even leads to polymerization reactions, thereby weakening the catalytic activity. Therefore, a low reaction temperature is generally preferred.

2) Most of the research on MOF-derived carbon materials is still focused on preparation and characterization, but the study of their mechanism in the reaction is not yet mature.

There is an urgent need to thoroughly understand and master the interfacial interaction between MOF and other components, because they can provide guidance for optimizing the synthesis process of MOF-derived carbon materials to improve performance.

3) Although some strategies have been recommended to enhance the robustness between the MOF film and the carrier, such as spin-on polymer adhesives or alkyl functionalized carriers, they have no commercial value. Therefore, a general-purpose, low-cost and easy-to-operate strategy is needed.

Source of information: Nanowerk

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