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High Energy Institute has made progress in the research of photocatalytic nitrogen fixation
[ Instrument network instrument research and development ] Recently, the nuclear energy chemistry research group of the Multidisciplinary Center of the Institute of High Energy Physics, Chinese Academy of Sciences has made progress in the field of metal-organic framework materials photocatalytic nitrogen fixation. Researcher Shi Weiqun’s team reported two cases of free radical MOFs based on viologen ligands Materials Gd-IHEP-7 and Gd-IHEP-8.
The MOFs materials all exhibit excellent photocatalytic nitrogen fixation activity, with ammonia generation rates of 128 and 220 μmol h-1 g-1, respectively. The nitrogen fixation efficiency of Gd-IHEP-8 is 17 times higher than that of similar materials in the literature. At the same time, the researchers systematically explained the mechanism of MOFs materials for efficient nitrogen fixation for the first time. Analysis shows that Gd-IHEP-7 is a porous frame based on a two-dimensional layered structure. After heating in the air, Gd-IHEP-7 will undergo a transformation from a two-dimensional layered structure to a three-dimensional pore structure, thereby generating Gd-IHEP- 8. The viologen ligands in the two MOFs materials exist in the form of stable single free radicals. It is this stable long-lived free radical and the corresponding free radical-radical interaction that make the MOFs material display in the range of 200-2500nm Broad spectrum absorption to achieve visible light catalytic nitrogen fixation. Compared with Gd-IHEP-7, in the N2 reduction process, the intermediate formed by Gd-IHEP-8 and the oxygen atoms around the metal ion will form a denser hydrogen bond network, which can effectively reduce the free energy of the system, so that Gd-IHEP-8 shows higher photocatalytic nitrogen fixation efficiency.
This research provides a new strategy for the design and development of new nitrogen fixation photocatalysts based on MOFs materials. The related results are titled Solar-Driven Nitrogen Fixation Catalyzed by Stable Radical-Containing MOFs: Improved Efficiency Induced by a Structural Transformation and published in "Germany Applied Chemistry". The research was supported by the National Outstanding Youth Fund Project and the National Natural Science Foundation of China.