具有长激发态寿命和强可见光吸收钌(II)配合物光敏剂的制备及其光解水产氢性能研究

Photosensitizers(PSs) have played a significant role in the process of photocatalytic hydrogen evolution. They’re a mediator of electron transfer between electron donors and photocatalysts, and a main body of light absorption. However, traditional Ru(II), Ir(III) and Pt(II)-based complexes with 3MLCT excited states generally show relatively short-lived excited state lifetime and low molar extinction coefficient in visible range, which severely frustrate the efficiency of hydrogen production. In order to overcome the drawbacks of traditional PSs, we put forward to use Ru(II)-based complexes with 3IL excited states or 3MLCT/3IL equilibrium states as PSs for photocatalysis. The detailed work is as follows: a series of Ru(II) complexes with long-lived 3IL excited states will be prepared, their excited state lifetimes and excited state redox potential will be optimized by adjusting the number and location of decorating units to enhance the electron transfer efficiency. Ru(II) complexes with strong light-absorption ability in visible region will be synthesized by introducing the chromphores with strong visible-light-harvesting ability to the parent complexes to enhance the utilization efficiency of solar energy. At last, a comparative study of the electron transfer mechanism between constant catalyst and different types of Ru(II)-based PSs with 3MLCT state, 3IL state and 3MLCT/3IL equilibrium state will be carefully performed. In this project, we aim to construct the high-efficient photocatalytic system by developing new types of PSs.

在光解水产氢体系中，光敏剂是吸光的主体部分和电子转移的桥梁，发挥着至关重要的作用。然而，传统的钌、铱和铂等3MLCT型(金属到配体电荷转移)光敏剂存在激发态寿命短(几百个纳秒)与可见光吸收能力弱的问题(摩尔消光系数<10000M-1cm-1)，致使产氢体系内的分子间电子转移效率和可见光利用率较低。本项目针对上述问题，致力于合成3IL型(激发态定域于配体)与3MLCT/3IL型(两者能级接近，能量平衡)钌配合物光敏剂，并将其应用于光解水产氢研究。通过调节引入基团的数量和位置，合成具有长激发态寿命的3IL型钌配合物，优化激发态氧化还原电位，提高光敏剂到催化剂的电子转移效率；通过引入强吸光基团，合成具备强可见光吸收能力的钌配合物，提高光能利用率。研究比较3MLCT、3IL和3MLCT/3IL三种类型光敏剂与催化剂分子间的电子转移机制，拓宽可选用的光敏剂类型，以期构建高效的光催化产氢体系。

太阳光驱动水分解制备氢气是一种清洁的产能方式，有望解决当前面临的环境污染和能源危机问题。因此开发高效的光催化产氢体系具有重要的意义。针对当前催化产氢体系中所用光敏剂的类型单一、活性低、稳定性差、催化机制不明确等问题，开展了一系列研究：1 证实 3IL型光敏剂催化性能和稳定性显著优于传统3MLCT类型光敏剂；2 借鉴自然光合系统，提出将吸光中心和氧化还原中心分离策略，提升了光敏中心吸光能力和激发态寿命，其催化活性比传统Ru(bpy)23+提高12倍；3 通过共敏化策略，将蓝光吸收香豆素6和绿光吸收氟硼吡咯共同修饰到母体铱配合物中心，制备出具有强宽光谱吸收能力的光敏剂，其产氢转化数达到11万以上，比传统Ir(ppy)3+高320倍，是当前产氢活性最高的分子光敏剂；4 利用n→π跃迁策略，构建不含重原子的双香豆素光敏剂用于水分解制备氢气；5 通过跨键能量转移策略，利用强吸光氟硼吡咯敏化铜配位中心，大幅度提升铜基配合物可见区吸光能力和激发态寿命，其催化活性显著优于传统贵金属光敏剂；6将光敏中心和催化中心共同修饰到柔性聚合物链上，拉近两者之间的距离，将分子间的传输过程转变为分子内的过程，提升电子传输效率和催化性能。此外，将传统卟啉分子与锆金属节点组装成多孔金属有机框架，进一步限域亚纳米铂团簇，实现高效协同催化制备重要药物中间体，该光催化剂可循环利用超过10次且没有活性损失。