基于配体光生电荷的可见光响应MOFs材料设计合成与性质研究

Metal-organic frameworks (MOFs) materials have received much attention due to their unique features of versatile structures, large surface area, the great flexibility of syntheses and the feasible accessibility of multiple functionalities, as well as their wide-range potential applications for energy storage, gas storage, host-guest chemistry, catalysis and so on. Solar energy is the most abundant renewable energy which can be used directly without any environmental pollutant, therefore the use of solar energy is an effect way to fulfill the energy need and environmental concern. It is a great challenge for researchers to convert sunlight directly into electrical and chemical energy by using MOFs materials. This proposal is expected to synthesize novel porous MOFs with charge photogeneration phenomenon which is the basis of natural photosynthesis and photovoltaic effect. In order to achieve this goal, we propose that such MOFs materials can be synthesized by using rationally designed organic ligand with charge photogeneration property. The ligands with desired function will be synthesized from organic molecules showing excellent photoelectric properties, and the visible light absorption can be calculated predictably by quantum chemical calculation which would increase the rationality and feasibility of the study. Novel MOFs with ligand-based charge generation would be synthesized by coordination interaction between inorganic metal ions and the designed ligands. Moreover, the porosity of the MOFs structures would facilitates the guest molecules loading where the host-guest chemistry concerning electrical interaction between ligand and guest molecules would be carried out. Furthermore, the visible-light photocatalytic properties and photovoltaic behavior could be modulated by various MOFs, supporting more understanding between the structures and properties. We particularly expect that several MOFs show special catalytic activation and high photovoltaic properties could be prepared. In summary, we expected that more useful information could be obtained by the implementation of this proposal, which would help for rational design of such functional mateirals and understanding the charge photogeneration in MOFs.

金属有机骨架材料（Metal-Organic Frameworks, MOFs）具有合成灵活、结构多样、比表面积大、易功能化等特点，在储能、吸附、催化、主客体化学等方面的潜在应用而受到广泛的关注。太阳能是人类可直接利用的再生清洁能源，具有低成本、无污染的优点，利用太阳能对于当前亟待解决的新能源需求及环境保护等问题具有重要意义。如何使MOFs材料在可见光激发下产生光生电荷从而实现对太阳能的利用，将是MOFs材料研究者们面临的新问题，也极具挑战性。本课题拟从具有优异光电性质的有机小分子为起始原料，以功能为导向，在量子化学计算指导下精心设计合成具有可见光光生电荷性质的有机配体，通过适当的晶体生长方法合成新型金属有机骨架材料。期望获得系列具有较高稳定性的可见光光生电荷性质MOFs材料，研究材料光生电荷机理、主客体相互作用下的界面电荷迁移过程，探索材料可见光光催化和光伏性能。

高效开发利用清洁可再生的太阳能为解决当前面临的能源和环境问题提供了可行性方案。在众多类型具有光生电荷性质的物质中，新近发展的金属有机骨架（MOF）材料展现了丰富的骨架结构及可剪裁的化学组成，为高效利用太阳能提供了新平台。利用MOF材料高效利用太阳能的研究正处于起步阶段并逐渐成为化学和材料等研究领域的热点。如何设计合成具有高效光生电荷性质的MOF材料和明确其光生电荷物理机制成为这一研究的关键性问题和指导原则。.本项目研究旨在从光功能化有机配体出发构筑高效可见光吸收的MOF材料，明确材料的光生电荷本质并合理调控电荷迁移路径实现光化学转化从而高效利用太阳能。研究主要成果包括：（1）以具有优良光电功能的小分子，如蒽官能团等，为核心设计合成高度共轭的有机配体，通过适当的晶体生长技术构筑了系列具有新颖结构特征和高效可见光吸收性质的MOF材料，并对所合成的MOF进行细致的物理化学性质研究。（2）通过光谱、电化学、表面光电压和原位顺磁共振等技术对这些可见光响应MOF的光生电荷过程进行研究。实验发现可见光吸收配体光致激子可以有效电荷分离，通过配体到金属的电荷迁移或者界面电荷迁移过程形成配体自由基物种。（3）调控光生电子界面迁移过程并利用光致配体自由基，我们拓展了MOF光化学转化的反应类型，首次实现了MOF引发的活性自由基聚合并实现了高效可见光光催化二氧化碳还原，污染物降解和有机胺偶联以及硫化物加氧氧化等光化学反应。（4）成功探索并发展了通过在绝缘性的MOF中构筑长程空间电荷迁移路径实现MOF的导电性质。利用所合成导电MOF的结构特征和物化性质实现了MOF的电致发光和高选择性阻抗式化学传感。.上述项目研究成果为设计合成新型MOF材料高效利用太阳能提供了实验和理论基础。