Abstract Hybrid composites of phosphomolybdic acid@UiO-66 (PMo12@UiO-66) and Co-substituted phosphomolybdic acid@UiO-66 (PMo11Co@UiO-66) were synthesized using the direct solvothermal method. A variety of characterization results demonstrated that phosphomolybdic acid (PMo12) or Co-substituted phosphomolybdate acid (PMo11Co) clusters are uniformly dispersed in the cages of Zr-based metal-organic UiO-66 frameworks. The catalytic properties of these hybrid composites were investigated by applying the epoxidation of olefins with tert-butyl hydroperoxide as the oxidant. Compared to PMo12@UiO-66, PMo11Co@UiO-66 showed a much higher catalytic activity and was simply recovered by filtration and reused for at least ten runs without significant loss of catalytic activity. Particularly, PMo11Co@UiO-66 can efficiently convert cyclic olefins like limonenes to epoxides, and its selectivity to 1,2-limonene oxide reached 91% in the presence of a radical inhibitor such as hydroquinone. The excellent catalytic activity and stability of the hybrid composite PMo11Co@UiO-66 are mainly attributed to the uniform distribution of highly active PMo11Co units within the smaller cages of UiO-66, to the suitable surface polarity of the hybrid composite for facilitating the access of reagents and solvent, and to the strong interface-interactions between the polyoxometalate and the UiO-66 framework.

中文翻译：

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溶剂热合成 UiO-66 骨架共取代磷钼酸在烯烃环氧化中的催化应用

摘要 采用直接溶剂热法合成了磷钼酸@UiO-66（PMo12@UiO-66）和共取代磷钼酸@UiO-66（PMo11Co@UiO-66）的杂化复合材料。各种表征结果表明，磷钼酸（PMo12）或共取代磷钼酸（PMo11Co）簇均匀分散在基于锆的金属有机 UiO-66 骨架的笼子中。通过使用叔丁基氢过氧化物作为氧化剂的烯烃环氧化来研究这些杂化复合材料的催化性能。与 PMo12@UiO-66 相比，PMo11Co@UiO-66 显示出更高的催化活性，只需通过过滤回收并重复使用至少 10 次，催化活性没有显着损失。特别，PMo11Co@UiO-66可以有效地将柠檬烯等环烯烃转化为环氧化物，在对苯二酚等自由基抑制剂存在下，其对1,2-柠檬烯氧化物的选择性达到91%。杂化复合材料 PMo11Co@UiO-66 优异的催化活性和稳定性主要归因于高活性 PMo11Co 单元在 UiO-66 较小笼内的均匀分布，以及杂化复合材料合适的表面极性，有利于进入试剂和溶剂，以及多金属氧酸盐和 UiO-66 骨架之间的强界面相互作用。