Kawanishi, Japan, Nov. 15, 2022 /PRNewswire/ — Environmental issues such as climate change, natural resource depletion, species extinction, plastic pollution and deforestation are exacerbating around the world due to a population explosion.
        Carbon dioxide (CO2) is a greenhouse gas and one of the main causes of climate change. In this regard, a process known as “artificial photosynthesis (CO2 photoreduction)” can produce organic feedstock for fuels and chemicals from CO2, water and solar energy, just as plants do. At the same time, they also reduce CO2 emissions, since CO2 is used as a feedstock for the production of energy and chemical resources. Therefore, artificial photosynthesis is considered one of the latest green technologies.
        MOFs (Metal Organic Frameworks) are ultraporous materials composed of clusters of inorganic metals and organic linkers. They can be controlled at the molecular level in the nanometer range and have a large surface area. Due to these properties, MOFs can be applied in gas storage, separation, metal adsorption, catalysis, drug delivery, water treatment, sensors, electrodes, filters, etc. Recently, MOFs have been found to have CO2 capture ability that can be photoreduced CO2, that is, artificial photosynthesis.
        Quantum dots, on the other hand, are ultrathin materials (0.5–9 nm) whose optical properties conform to the rules of quantum chemistry and quantum mechanics. They are called “artificial atoms or artificial molecules” because each quantum dot consists of only a few or a few thousand atoms or molecules. In this size range, the energy levels of the electrons are no longer continuous and become separated due to a physical phenomenon known as the quantum confinement effect. In this case, the wavelength of the emitted light will depend on the size of the quantum dots. These quantum dots can also be applied in artificial photosynthesis due to their high light absorption capacity, ability to generate multiple exciton and large surface area.
        Both MOFs and quantum dots have been synthesized under the Green Science Alliance. Previously, they have successfully used MOF quantum dot composite materials to produce formic acid as a special catalyst for artificial photosynthesis. However, these catalysts are in powder form and these catalyst powders must be collected by filtration in each process. Therefore, since these processes are not continuous, they are difficult to apply for practical industrial use.
        In response, Mr. Tetsuro Kajino, Mr. Hirohisa Iwabayashi, and Dr. Ryohei Mori of Green Science Alliance Co., Ltd. used their technology to immobilize these special artificial photosynthesis catalysts on inexpensive textile sheets and developed a new process for the production of formic acid. which can operate continuously in practical industrial applications. After the completion of the artificial photosynthesis reaction, the water containing formic acid can be taken out for extraction, and new fresh water can be added back to the container to continuously resume artificial photosynthesis.
        Formic acid can replace hydrogen fuel. One of the main reasons preventing the spread of a hydrogen society around the world is that hydrogen is the smallest atom in the universe, so it is difficult to store it, and the production of a hydrogen tank with a high sealing effect will be very expensive. In addition, hydrogen gas can be explosive and pose a safety hazard. Since formic acid is a liquid, it is easier to store as a fuel. If necessary, formic acid can be used to catalyze the production of hydrogen in situ. In addition, formic acid can be used as a raw material for various chemicals.
       Although the efficiency of artificial photosynthesis is still low, the Green Science Alliance will continue to fight for efficiency improvements to establish practical applications for artificial photosynthesis.