Zhao Wenshi, Shi Yanan, Jiang Yuheng, Zhang Xiaofei, Long Chang, An Pengfei, Zhu Yanfei, Shao Shengxian, Yan Zhuang, Li Guodong, Tang Zhiyong
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China.
School of Nanoscience and Technology, University of Chinese Academy of Sciences, Beijing, 100049, P. R. China.
Angew Chem Int Ed Engl. 2021 Mar 8;60(11):5811-5815. doi: 10.1002/anie.202013807. Epub 2021 Feb 1.
Direct methane oxidation into value-added organic oxygenates with high productivity under mild condition remains a great challenge. We show Fe-O clusters on nodes of metal-organic frameworks (MOFs) with tunable electronic state for direct methane oxidation into C1 organic oxygenates at 50 °C. The Fe-O clusters are grafted onto inorganic Zr nodes of UiO-66, while the organic terephthalic acid (H BDC) ligands of UiO-66 are partially substituted with monocarboxylic modulators of acetic acid (AA) or trifluoroacetic acid (TFA). Experiments and theoretical calculation disclose that the TFA group coordinated with Zr node of UiO-66 enhances the oxidation state of adjacent Fe-O cluster due to its electron-withdrawing ability, promotes the activation of C-H bond of methane, and increases its selective conversion, thus leading to the extraordinarily high C1 oxygenate yield of 4799 μmol g h with 97.9 % selectivity, circa 8 times higher than those modulated with AA.
在温和条件下将甲烷直接氧化为具有高生产率的增值有机含氧化合物仍然是一个巨大的挑战。我们展示了金属有机框架（MOF）节点上具有可调电子态的Fe-O簇，可在50°C下将甲烷直接氧化为C1有机含氧化合物。Fe-O簇接枝到UiO-66的无机Zr节点上，而UiO-66的有机对苯二甲酸（H BDC）配体部分被乙酸（AA）或三氟乙酸（TFA）的单羧酸调节剂取代。实验和理论计算表明，与UiO-66的Zr节点配位的TFA基团由于其吸电子能力增强了相邻Fe-O簇的氧化态，促进了甲烷C-H键的活化，并提高了其选择性转化，从而导致4799 μmol g h的异常高的C1含氧化合物产率，选择性为97.9%，比用AA调节的产率高约8倍。
