基于共价有机框架光热催化剂的可控构筑及其对二氧化碳合成苯甘氨酸衍生物的调控

To solve these intractable problems including low activity of carbon dioxide or harsh conditions in the conversion of carbon dioxide into fine organic chemicals, visible photothermal responsive covalent organic framework-based catalysts were designed and prepared. These catalysts will be investigated for their regulation on the selective synthesis of non-natural phenylglycine derivatives from carbon dioxide and benzylamines via the sp3 C-H direct carboxylation. Due to the low visible-light responsive value caused by the too wide or narrow band gap of conventional covalent organic frameworks, we will innovatively employ largely conjugated aromatic alkynes as building blocks to synthesize covalent organic framework materials. Following that, the metal salts, nanoparticles, or semiconductor species will be assembled in/on these materials by several methods, such as photochemical reduction, to broaden the response range of visible light. Finally, the covalent organic framework-based heterojunction catalysts with stable structure and wide response range of visible light were prepared. Technical characterizations, such as CO2 adsorption-desorption and UV-vis diffuse reflectance, will be performed to investigate the effect of the structure of catalysts in the CO2 conversion, and the structure-activity relationship between structure and performance is finally established. In situ IR spectrum and density functional theory calculations will be also employed to understand the transformation process and mechanism. The green synthesis methodology of non-natural phenylglycines will be finally developed, which is of significant meanings and application values.

针对二氧化碳转化为精细有机化学品反应中存在的反应物活性低、条件苛刻等问题，本项目拟设计并构筑具有可见光热响应的共价有机框架基催化剂，并研究其对二氧化碳和苄胺通过sp3 C-H键羧基化选择性合成非天然苯甘氨酸衍生物反应的调控。由于常规共价有机框架带隙过宽或过窄导致其可见光响应值低，本项目创新性地以大共轭体系芳香炔化合物作为构筑基元合成共价有机框架材料，并通过光化学还原法等方法将金属盐、纳米粒子或金属半导体等组装于材料中，拓宽其可见光响应范围，制备出结构稳定、可见光响应范围宽的共价有机框架基异质结催化剂。将通过二氧化碳吸附-脱附、紫外-可见光吸收等表征手段研究共价有机框架基催化剂结构对二氧化碳转化反应的影响，建立结构与性能之间的构效关系。将通过原位红外光谱等表征并结合密度泛函理论计算研究二氧化碳转化反应机理。最终，建立苯甘氨酸衍生物等精细有机化学品的绿色新工艺，具有重要的理论意义和应用价值。

通过光催化技术将CO2转化为高附加值有机燃料或精细化学品，为工业废气资源利用和缓解全球气候变化提供了极具潜力的途径。然而，CO2自身热力学稳定、动力学惰性、活化困难，如何实现高转化率和高选择性是需要突破的瓶颈问题，而设计高效的催化剂是关键所在。多孔晶态共价有机框架材料具有可调变的组分及结构、超大的共轭结构和规律的周期性排列，为CO2吸附与活化提供了一个极具潜力的多功能平台。但大多数材料由于可见光利用率低、光生载流子严重复合、缺乏催化位点等问题导致其催化活性难以令人满意。本项目通过引入炔基拓展骨架、结构与形貌工程、界面调控、催化位点修饰等策略合成了系列高效的共价有机框架光/热催化剂，并将其应用于光/热催化CO2转化为高附加值有机燃料和精细化学品、光催化选择性氧化反应中的系统探究其催化性能，最终实现温和条件下各类重要精细化学品的绿色合成。通过全面的表征手段与理论计算深入研究并揭示了催化剂结构、电荷分离与催化性能之间构-效关系。通过原位光谱技术等深入研究催化剂在真实催化条件下对反应体系的作用机制。本项目研究得到的代表性结论如下：（1）通过共轭炔基为“桥”连接供体和受体单元，拓宽其电荷的迁移距离，可有效提升其分离效率及载流子寿命；（2）通过溶剂效应、结构单元及合成条件调控结构与形貌可显著增强其电荷分离和迁移能力，并清晰阐释共价有机框架结构与催化性能之间的构-效关系；（3）利用静电作用引入负电性氮化硼进入共价有机聚合物，诱导光生空穴向定向迁移，显著增强光生电荷分离并抑制其复合；（4）采用非线性吡啶基单体为前驱体通过调整吡啶N位置以限制金属纳米颗粒在其孔道内的成核和生长调控其催化活性本项目集材料制备、光催化CO2还原、有机转化、构-效关系等关键科学问题研究于一体，符合我国“碳中和”和绿色发展国家战略，为催化剂的设计与合成提供了重要的理论指导。

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