可见光驱动还原CO2的多核廉价金属配合物制备及催化机理研究

The greatest crises confronting us in twenty-first century are the threat from global warming and the rapidly growing demand for energy. From the views of carbon balance and energy balance, an ideal solution to these problems can be the utilization of solar energy to produce useful fuels from CO2. The design of efficient catalyst plays a key role in the conversion of CO2. The most challenges are the utilization of abundant and cheap elements for catalyst preparation, extending the response to the visible light region, improving of catalysis efficiency, and enhancing the products selectivity. The primary goal of this project is to develop the artificial photocatalysis systems to convert CO2 and H2O to hydrocarbons under the visible-light irradiation. The multinuclear metal complexes will be synthesized from abundant cheap metals (Zn, Co, Ni) replacing traditional used rare precious metals. Step-by-step methods will be used for the single molecular photocatalysts contain photosensitizers and catalytic centers which are connected with covalent linkage. The single molecular photocatalysts perform the conversion CO2 to useful fuel with responds to the visible light. Then the single molecular photocatalysts are fully characterized by NMR, mass spectra, and single crystal X-ray diffraction. Under the visible-light irradiation, the single molecular photocatalysts are used to catalyze CO2 conversion. The properties of catalysis such as efficiency for visible-light utilization, catalyst stability, catalytic efficiency, and products selectivity will be carefully investigated using several technologies such as transient absorption, in-situ IR, isotope trace, NMR, and mass spectroscopy. With the aid of density functional theory calculations (DFT), the mechanism of CO2 reduction based on the single molecular photocatalysts are investigated. Through these attempts, more efficient visible-light driven artificial photocatalysts for CO2 conversion could be constructed.

高效催化材料是光催化还原CO2的基础，采用地球上丰富的廉价元素、拓宽光催化材料的光响应范围、提高CO2转化效率和产物专一性是催化材料设计制备面临的迫切要求。本研究采用廉价金属（锌、钴、镍）配合物制备高效稳定的多核光催化材料代替稀有贵金属催化剂，利用分步合成方法将光敏中心和催化中心通过碳碳共价键连接起来，制成可见光驱动还原CO2的单分子光催化材料。利用瞬态吸收、原位红外、同位素示踪、核磁共振、色谱等多种检测技术手段研究单分子光催化材料对光能利用效率、稳定性、催化效率、产物选择性。结合量子化学理论计算方法，探讨单分子光催化材料的构效关系和催化机理。本研究将为可见光驱动CO2资源化反应涉及的高效廉价催化材料设计制备和催化机理研究提供新途径和新思路，对解决全球气候变化和能源短缺问题具有重要的理论意义和实用价值。

针对采用廉价元素、拓宽光响应范围、提高转化效率、提高产物选择性等光催化CO2还原反应的迫切要求，从理论设计、光催化材料制备和应用层面上，探索可见光驱动还原CO2的廉价单分子分散光催化材料，研究光催化还原CO2反应的物理化学机制。开展以下研究工作：（1）提出高效廉价金属光催化材料制备方法，通过分步合成方法将具有可见光响应的光敏中心和具有CO2催化还原的催化中心以化学键形式连接起来，构建多功能单分子分散的光催化材料；（2）基于制备的催化材料，在有机溶液和水溶液等环境下构建相应的光催化还原CO2反应体系，提高了催化材料的应用范围；（3）探讨单分子分散光催化材料中桥联官能团的作用机制，研究多种化学键（碳碳键、羧酸根、磷酸根、质子化氢）在光催化还原CO2反应中的作用，初步理解反应电子传递的结构要求；（4）通过调控反应体系组分等参数，控制反应过程中CO2还原产物（CO、甲酸、甲醇）的选择性，初步掌握提高目标产物专一性的分子结构要求；（5）通过载体结构和形貌的优化，提高光催化材料的稳定性和实用性。本研究为可见光驱动CO2资源化设计的高效催化材料设计制备和催化机理研究提供新方法和新思路，对解决全球气候变化和能源短缺问题具有重要的理论意义和实用价值。