Research on Phetoreduction System for Supercritical Carbon Dioxide

为了开发能够高效、实用地利用可见光将CO_2还原为CO_2的分子体系，本论文从以下三个方面对新型Ru(Ru)和Co(Co)多吡啶络合体系进行了研究。高效金属络合物催化剂的开发为了开发高效的光诱导电子转移金属络合物体系，通过共轭碳链将Ru和Co络合物单元连接起来，研究了新型双分子络合物。结果表明：1.电子转移速度较快，但反向电子转移速度加快，CO_2还原效率没有提高。金属络合物寿命的提高和固体催化体系的发展将阳离子Ru和Co络合物固定在离子交换聚合物上，考察了其光诱导CO_2还原能力。结果表明：1)固体催化体系易于处理和回收金属络合物；2)虽然每次光照射的效率没有提高，但络合体系的寿命延长，生成的CO总量增加。超临界CO_2反应体系的开发为了建立高压或超临界CO_2下的反应体系，研制了反应容器，并对光还原反应条件进行了研究。结果表明，有机溶剂-超临界CO_2两相体系具有较高的CO_2还原速率。现已对该体系的重现性进行了详细的考察，并对超临界CO_2相下的新体系进行了研究。

In order to develop the molecular system, which can efficiently and practically reduce CO_2 to CO as a chemical resource using visible light, new ruthenium (Ru) and cobalt (Co) polypyridine complex-system was investigated from the following three points.1. Development of efficient metal complex catalystsIn order to develop efficient photo-induced electron transfer metal complex systems, Ru and Co complex units were connected by conjugated carbon chain and the new bimolecular complex was investigated. As a result, fast electron transfer was observed but back electron transfer was also accelerated and no improvement of CO_2 reduction efficiency was attained.2. Improvement of metal complex life time and development of solid catalytic systemCationic Ru and Co complexes were fixed to ion exchange polymer and its photo-induced CO_2 reduction ability was investigated. As a result, the followings were found : 1) Solid catalytic system is easy to handle and recover the metal complexes ; 2) Although the efficiency was not improved for each photoirradiation, the life time of the complex system became long and the total amount of CO produced was increased.3. Development of supercritical CO_2 reaction systemIn order to establish a reaction system under high pressure or supercritical CO_2, a reaction vessel was developed and reaction conditions were investigated for photo-reduction. As a result, high CO_2 reduction rate was obtained under organic solvent-supercritical CO_2 two phase system. Now the reproducibility is examined in detail and investigation of a new system under supercritical CO_2 phase is also on going.