纳米TiO2-超交联聚合物杂化材料的结构设计及光催化还原CO2研究

According to the current environment and energy issues that caused by greenhouse effect and carbon resources shortage, it is of great significance for developing solar photocatalytic technology with low-energy consumption in fields of CO2 conversion. The project is stimulated by the shortcomings of TiO2 photocatalysts such as low CO2 adsorption, visible-light utilization and quantum efficiency. The conjugated carbon (or carbon nitride) materials are introduced as the supports for growing nano-sized TiO2 crystals and facilitating the electrons transfer. Then the TiO2 hybridized hypercrosslinked polymer materials are constructed by knitting the support framework with an external crosslinker. Different from the traditional type of porous materials supported photocatalysts, this new strategy of constructing microporous polymer networks around the photocatalysts, can largely maintain their structural superiority. This strategy simultaneously combines the excellent electrons transfer efficiency of supporting materials and high CO2 adsorption as well as wide spectral response ability of microporous polymers. Hence it is more favorable for improving the utilization of solar energy and CO2 conversion efficiency of TiO2 photocatalysts. Based on it, the theoretical calculation is also involved in the molecular design and screening of the polymer materials. The efficiency and selection of CO2 adsorption and conversion can be further improved by structure and heteroatom adjustment. Through studying the relationship between the structural properties and photocatalytic efficiency/selection/mechanism of hybrid materials, we will propose the regulation mechanism of photocatalytic reaction and the possible directions for improvement of photocatalytic performance.

根据温室效应与碳资源短缺引起的环境和能源问题现状，发展低能耗的太阳能光催化转化CO2技术具有重要意义。针对目前TiO2光催化剂较低CO2吸附能力、可见光利用率及量子效率的缺陷，本项目引入共轭碳(氮)材料作为纳米TiO2生长的载体和电子转移助剂，然后对载体骨架外交联编织，制备纳米TiO2-超交联聚合物杂化材料。不同于传统的孔材料负载型光催化剂，这种从催化剂外围构建微孔聚合物网络制备杂化材料的新策略，较大程度保持了其结构优势，同时结合了载体材料优异电子传输性能和微孔聚合物较高CO2吸附与宽光谱响应能力，从而更有益于TiO2光催化剂对太阳光的利用率和CO2催化转化效率。在此基础上，结合理论计算对聚合物材料进行分子设计和筛选，通过结构与杂原子调控进一步提高CO2吸附与转化的效率和选择性；分析总结杂化材料的结构性质与光催化效率/选择性/机理的关系规律，提出光催化反应影响机制以及性能提升的发展方向。

根据温室效应与碳资源短缺引起的环境和能源问题现状，发展低能耗的太阳能光催化转化CO2技术具有重要意义。针对目前TiO2光催化剂较低CO2吸附能力、可见光利用率及量子效率的缺陷，引入碳（氮）材料作为纳米TiO2生长的载体和电子转移助剂，然后对TiO2周围的碳骨架外交联编织，构筑纳米TiO2-超交联聚合物（HCPs）杂化材料。不同于传统的孔材料负载型光催化剂，这种从催化剂外围构建微孔聚合物网络制备杂化材料的新策略，较大程度保持了其结构优势，同时结合了载体材料优异电子传输性能和微孔聚合物较高CO2吸附与宽光谱响应能力，从而更有益于对太阳光的利用率和CO2转化效率。.主要研究内容分为四个部分：① 碳（氮）材料负载TiO2复合光催化剂；② 微孔材料杂化TiO2复合光催化剂的制备与结构调控；③ 超交联多孔聚合物的分子设计调控金属催化剂结构与性能；④ 聚合物与TiO2气固相光催化CO2还原的反应体系优化。取得的重要结果及关键数据为：制备出负载均匀、具有较高比表面积与载流子传输效率的TiO2-HCPs杂化材料，比表面积高达988~1535 m2 g-1，在没有牺牲剂存在下，模拟太阳光全光谱激发下气-固相催化转化CO2生成CO或CH4的产率分别达到39和51 μmol g-1 h-1，并提出了复合材料的光生载流子迁移机理与光催化转化CO2机制，根据建立的构效关系导向HCPs的分子设计，进一步调控Pd催化剂的分散性，实现CH4的高选择性生成（237.4 μmol g-1 h-1）。.本项目提出了光催化剂表面原位编织微孔聚合物的组装新策略，不仅导向光生电子向表面还原活性中心的快速迁移，更重要的是，突破性改善比表面积并丰富了孔结构。在气-固可见光催化系统，初步实现了低浓度CO2的高效吸附、扩散及光催化转化，将给低浓度CO2排放控制与资源化技术的发展提供新思路，拓展在环境净化和能量转换领域的应用。