From Better Performance to Future Development: The Role of Metal-Organic Frameworks (MOFs) in Electrocatalysis

Electrocatalysis as an effective energy storage and conversion technology opens up a new path to solve the current problems of energy depletion and environmental pollution caused by consumption of fossil fuels. Metal-organic frameworks (MOFs), a class of crystalline porous materials with a high specific surface area, high porosity and designable structure, have shown great potential as novel electrocatalysts. However, the inherent low electrical conductivity and low stability of MOFs have significantly impeded their further application in electrocatalysis.

How to design and synthesize highly stable and conductive MOFs, energy regulation of the electrocatalytic reaction intermediates in MOFs and adsorption strength of active species are the keys to optimizing the electrocatalytic performance. Based on the above ideas, a large number of electrocatalysts based on MOFs have been newly reported in recent years. Therefore, it is necessary to provide a timely summary of the latest progress. Lee et al. Post their opinion on Industrial chemistry and materials.

“Developing efficient, green, and low-cost electrocatalysts based on MOFs is critical to addressing current problems of energy depletion and environmental pollution caused by fossil fuel consumption,” said Jiandong Pang, a professor at Nankai University. .

“In this review, we systematically summarize research progress in the application of MOFs in electrohydrogen evolution reactions (HER), hydrogen oxidation reactions (HOR), oxygen evolution reactions (OER), oxygen reduction reactions (ORR), and nitrogen reduction. reactions (NRR) according to the categories of mono-MOFs, bi-MOFs, MOF-based composites, and MOFs as supports, revealing structure-property relationships.”

Strategies to enhance the stability and conductivity of MOF-based catalytic materials are also summarized. We also provided an overview of the opportunities and challenges facing MOF in electrical stimulation and listed the problems that need to be explored and resolved.

As a new type of crystalline porous material, MOFs are known for their predictable and diverse composition and design, high surface area, guest-accessible voids, and easily functionalized channels. MOFs are currently used in a wide range of different electrocatalytic reactions, including HER, HOR, ORR and OER.

These reactions lie at the heart of the following devices or cells: metallic air cells, renewable fuel cells, electrolytic water to hydrogen devices, and other important electrochemical energy conversion devices. Moreover, the electrocatalytic reduction of nitrogen to ammonia also shows attractive applications in the field of energy conversion.

Despite the many unique advantages of the electrocatalytic reactions mentioned above, their cost must be carefully considered in order to achieve commercialization. Therefore, it is necessary and urgent to design environmentally friendly, low energy consumption and highly stable MOF catalysts from the perspective of efficiency and cost.

“Synthesis of MOFs with predictable structures and high stability has been an important MOF research goal. A clear strategy to guide the design of linkers and metals will help in the development of new functional MOFs and provide a new fire reference for various MOFs,” Pang said.

“Synthesis with the same reactants may lead to MOFs with different structures and properties, and the reaction time, method, and temperature of synthesis will also affect the crystal structure, morphology, and pore environment of MOFs, which will further affect the performance of materials. There are two common tuning directions for the synthesis of catalysts MOF-based electrophoresis, that is, tuning the size of the MOFs and adjusting the conductivity of the MOFs.”

Moreover, based on the diversity of metal ions and ligands, specific metal centers and ligands containing specific organic functional groups can be selected to design and synthesize MOFs with high stability in a catalytic environment and apply them to the study of electrocatalysis. Stability, researchers generally choose to construct frameworks using ligands. Carboxyl-based (Lewis solid bases) and highly valent metal ions (Lewis solid acids, such as Al3+Commercial Record3+Fe3+Ti4+and Zr4+) or bonds based on azo (soft Lewis bases) and low-valent transition metal ions (soft Lewis acids, such as Co2+ne2+copper2+and Zn2+) based on the soft-solid acid-base (HSAB) theory. The designed metal structure possesses high stability and will greatly enhance the electrocatalysis performance, said Xian Hebo, a professor at Nankai University.

Pang said there is still a lot of room for improving MOF materials for electrocatalytic designs in the future. Incorporation of catalytically active ligands (such as porphyrins) into MOFs and modulation of the catalytic effect by tuning the pore environment and pore structure is an effective strategy to enhance electrocatalytic performance. In addition, forming MOFs with bimetallic active sites using diatomic metal groups/ions to improve the electronic structure and surface state of the metal centers is also a feasible strategy.

To maximize the benefits of MOFs, using MOFs as supports for loading metal nanoparticles or single metal atoms and synthesizing MOFs with inorganic active materials are also suggested strategies.

“In this review, our main goal is to provide readers with accurate and timely updates on the latest research developments and strategies for improving electrostimulation performance in this field, while providing an outlook on future developments in this field,” said Bo.