Tang Jia, Wei Fen, Ding Shujiang, Wang Xiaoxia, Xie Guanqun, Fan Hongbo
Department School of Environment and Civil Engineering, Dongguan University of Technology, Dongguan, 523808, P. R. China.
Department of Applied Chemistry, School of Science, Xi'an Jiaotong University, Xi'an, 710049, P. R. China.
Chemistry. 2021 Sep 6;27(50):12890-12899. doi: 10.1002/chem.202102089. Epub 2021 Aug 5.
Chemical fixation of CO as C1 source at ambient temperature and low pressure is an energy-saving way to make use of the green-house gas, but it still remains a challenge since efficient catalyst with high catalytic active sites is required. Here, a novel monoclinic azo-functionalized Zr-based metal-organic polyhedron (Zr-AZDA) has been prepared and applied in CO fixation with epoxides. The inherent azo groups not only endow Zr-AZDA with good solubilization, but also act as basic sites to enrich CO showing efficient synergistic catalysis as confirmed by TPD-CO analysis. XPS results demonstrate that the Zr active sites in Zr-AZDA possess suitable Lewis acidity, which satisfies both substrates activation and products desorption. DFT calculation indicates the energy barrier of the rate-determining step in CO cycloaddition could be reduced remarkably (by ca. 60.9 %) in the presence of Zr-AZDA, which may rationalize the mild and efficient reaction condition employed (80 °C and 1 atm of CO ). The work provides an effective multi-functional cooperative method for improvement of CO cycloaddition.
在环境温度和低压下将CO化学固定为C1源是利用温室气体的一种节能方式，但由于需要具有高催化活性位点的高效催化剂，这仍然是一个挑战。在此，制备了一种新型单斜晶系偶氮功能化的Zr基金属有机多面体（Zr-AZDA），并将其应用于CO与环氧化物的固定反应。固有的偶氮基团不仅赋予Zr-AZDA良好的溶解性，还作为碱性位点富集CO，TPD-CO分析证实其具有高效的协同催化作用。XPS结果表明，Zr-AZDA中的Zr活性位点具有合适的路易斯酸度，这既满足底物活化又满足产物脱附。DFT计算表明，在Zr-AZDA存在下，CO环加成反应中速率决定步骤的能垒可显著降低（约60.9%），这可以解释所采用的温和高效反应条件（80°C和1 atm的CO）。这项工作为改进CO环加成反应提供了一种有效的多功能协同方法。
