具有多光生电子输出通道石墨烯/卟啉组装体的构筑及其界面电子转移研究

Three-dimensional graphene/porphyrin assemblies show wide prospects in the fields of solar energy transformation and environmental pollution treatment. There exist some unsolved problems: weak linkage on the interface, severe conditions for the preparation, long reaction time, low photo-produced electron transfer efficiency, and absent transfer mechanism, which greatly restrict its development and application. The project lays stress on the following respects. A series of porphyrins with special functional groups at 5 and 15 positions are to be designed and synthesized. With them as pillared units, the graphene sheets pre-implanted metal ions are induced by coordination interaction and self-directed assemble in the vertical direction. Subsequently, a new type of three-dimensional graphene/porphyrin assemblies bridged with metal ions is achieved by combining electrostatic interaction with coordination interaction. As a result, the multichannels for producing and transferring photo-produced electrons are constructed in the vertical direction between adjacent graphene sheets so that light absorption and electron transfer efficiency are improved. By adjusting interfacial stress and energy barrier, the transfer of photo-produced electrons is regulated. By means of structural analysis, performance investigation and theoretical calculation, the influence of the interfacial stress and the energy barrier on steric configuration of the assembly is investigated. Furthermore, the mechanism for metal ions in regulating photo-produced electron transfer is illustrated. The development of the project will provide new ideas for the fabrication of graphene/porphyrin based functional materials, and for its continuing innovation in the fields of energy and environment.

石墨烯/卟啉三维组装体在能源转换、环境治理等领域应用前景广阔。目前存在界面联结力较弱、制备条件苛刻、耗时、光生电子转移效率较低且对转移机制认识不足等问题，这严重制约了它的进一步发展和应用。本项目拟通过设计、合成系列5, 15位带有特定官能团的卟啉分子，并以其为柱撑功能单元，通过配位作用诱导铆合金属离子的石墨烯纵向自导向组装，获得金属离子界面桥连的石墨烯/卟啉三维组装体。通过在相邻石墨烯片纵向构建多条光生电子产生和转移通道，提高光吸收和电子转移效率；还可以调节石墨烯与卟啉分子间界面应力和能垒（改变金属离子性质或卟啉分子结构）实现对组装体光生电子转移的调控。通过系统地结构分析、性能研究和理论计算，研究石墨烯/卟啉间界面应力和能垒对组装体空间构型的影响，阐明界面金属离子在调控电子转移过程中的作用机制。本项目的开展将为石墨烯/卟啉基功能材料的构筑及其在能源、环境等领域的持续创新研究提供新思路。

将太阳能转化为氢能、电能，被认为是未来解决能源短缺和环境污染问题的有效途径。石墨烯因具有易被修饰的共轭结构和良好的光学、电学等性能，在光电转换、光催化制氢和降解等与能源、环境相关的领域有良好的应用前景。相对于二维石墨烯，三维石墨烯既保持了石墨烯的原有特性，又避免了石墨烯片重新聚集而导致的比表面积减小、电子迁移率下降等问题，在催化、吸附、燃料电池和超级电容器等领域具有独特的优势。三维石墨烯的微观结构、制备方法直接影响其性能。因此，如何设计其微观结构、快速构筑光电转换效率高的三维石墨烯，进而深入研究其界面电子转移是开发新型、高效光电器件和催化剂实现其在能源、环境等领域实际应用需要考虑的关键问题。.本项目在石墨烯中引入电子结构互补的卟啉单体分子，并主要针对如何在石墨烯纵向实现与卟啉单体分子的连接，以及控制石墨烯/卟啉组装体激发态寿命的问题开展研究工作。首先，合成了5, 15位带有吡啶基、羧基等官能团的卟啉分子，借助非共价相互作用构筑了系列石墨烯/卟啉组装体，通过多种光谱技术并结合密度泛函理论计算阐明了石墨烯/卟啉的组装机理。继而，详细研究了组装体的激发态寿命、光催化析氢活性及光催化机理。发现：以5, 15-二(4-吡啶基)-10, 20-二苯基卟啉(DPyP)柱撑氧化石墨烯激发态寿命长、界面电阻低、光催化制氢性能高；以金属钴为桥联剂，DPyP分子与氧化石墨烯之间的柱撑角度加大，更有利于光的吸收和电子的转移。另外，通过构筑并研究系列氧化石墨烯/卟啉/芘磺酸组装体的光催化制氢性能和制氢机理，阐明了复合体系光催化活性提高的主要原因。在此基础上，将实验结果与理论计算结果相结合，深入研究了卟啉分子取代基的不同对其组装方式、性能的影响；通过将时间分辨荧光光谱及电子顺磁共振光谱等结果相结合阐明了组装体的光催化制氢机理。本项目不但为设计和开发合成方法简单、性能优异的石墨烯/卟啉功能组装体提供了新思路，也为其在能源领域应用提供理论指导和实验依据。