Green synthesis of COFs for environmental applications

With the increasing growth of global energy needs, the development of carbon-free and clean energy technologies has become more and more critical. Nuclear power, as one of the clean energies, supplies about 11% of the electricity around the world. The construction and expansion of nuclear energy has increased the widespread use of promising materials, such as rare earth elements (REE), actinides and technetium. However, before these "clean energy" technologies further develop to reach their full potential, they face several major obstacles. For example, nuclear fuel reprocessing and improper waste disposal are the biggest limitations of nuclear energy. Nuclear safety is another severe issue, because large-scale uranium mining and several nuclear accidents have resulted in many radioisotopes and the combination of radiotoxicity and chemical toxicity to the environment in the past few decades. In addition, the demand for these critical elements has also increased sharply due to the important applications, such as high-efficiency lighting, electric cars, portable devices and permanent magnets. Therefore, the development of novel materials and technologies to improve the nuclear fuel cycle has attracted widespread attention. In the past few decades, many functional porous adsorbents based on metal-organic frameworks, polymers, mesoporous silica, carbons, etc. have been designed and evaluated for radioisotope extraction. Under highly acidic conditions, such as in the case of wastewater treatment related to the nuclear fuel cycle, the above-mentioned materials exhibit very low adsorption effects, poor recyclability and selectivity. So far, there are few of materials that can meet all the requirements for true extraction and separation of REE and actinide elements. Covalent organic frameworks (COFs), one kind of crystalline porous polymers constructed via strong covalent bonds, may be an ideal candidate as solid sorbents because of their excellent properties such as low densities, good chemical stability, large specific surface area, and periodic pore structure. However, for the traditional solvothermal synthesis method, scale-up is a challenge. On the other hand, research on COFs is still in its infancy, and application for environmental remediation using COFs is limited to a few examples. This research will focus on using green synthesis methods to synthesize designed COFs on a large scale and studying the relationships between structure and extraction performance of targeted metals. Only water will be used as reaction solvent in the process of synthesis, which is scalable and environmentally friendly. The influence of pore size and amount of functional groups of COFs on the extraction performance of critical metals will be explored. Therefore, the proposed project could directly address some of the limitations by creating a platform for green synthesis of COFs and their applications directed to the fields of environmental remediation.

With the increasing growth of global energy needs, the development of carbon-free and clean energy technologies has become more and more critical. Nuclear power, as one of the clean energies, supplies about 11% of the electricity around the world. The construction and expansion of nuclear energy has increased the widespread use of promising materials, such as rare earth elements (REE), actinides and technetium. However, before these "clean energy" technologies further develop to reach their full potential, they face several major obstacles. For example, nuclear fuel reprocessing and improper waste disposal are the biggest limitations of nuclear energy. Nuclear safety is another severe issue, because large-scale uranium mining and several nuclear accidents have resulted in many radioisotopes and the combination of radiotoxicity and chemical toxicity to the environment in the past few decades. In addition, the demand for these critical elements has also increased sharply due to the important applications, such as high-efficiency lighting, electric cars, portable devices and permanent magnets. Therefore, the development of novel materials and technologies to improve the nuclear fuel cycle has attracted widespread attention. In the past few decades, many functional porous adsorbents based on metal-organic frameworks, polymers, mesoporous silica, carbons, etc. have been designed and evaluated for radioisotope extraction. Under highly acidic conditions, such as in the case of wastewater treatment related to the nuclear fuel cycle, the above-mentioned materials exhibit very low adsorption effects, poor recyclability and selectivity. So far, there are few of materials that can meet all the requirements for true extraction and separation of REE and actinide elements. Covalent organic frameworks (COFs), one kind of crystalline porous polymers constructed via strong covalent bonds, may be an ideal candidate as solid sorbents because of their excellent properties such as low densities, good chemical stability, large specific surface area, and periodic pore structure. However, for the traditional solvothermal synthesis method, scale-up is a challenge. On the other hand, research on COFs is still in its infancy, and application for environmental remediation using COFs is limited to a few examples. This research will focus on using green synthesis methods to synthesize designed COFs on a large scale and studying the relationships between the structure and extraction performance of targeted metals. Only water will be used as reaction solvent in the process of synthesis, which is scalable and environmentally friendly. The influence of pore size and amount of functional groups of COFs on the extraction performance of critical metals will be explored. Therefore, the proposed project could directly address some of the limitations by creating a platform for green synthesis of COFs and their applications directed to the fields of environmental remediation.