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<p>Enhancing the catalytic activity of catalysts is a core objective in their design and synthesis processes, and the accessibility of active sites is one of the crucial factors determining catalyst activity. Polyoxometalate-based metal-organic complexes (POMOCs) with well-defined structures, which combine the advantages of POMs and MOCs, may offer the possibility to construct catalysts with highly accessible active sites. In this study, a series of POMOCs were successfully designed and synthesized using different POM templates, including [Co<sup>II</sup><sub>1.5</sub>(L)<sub>1.5</sub>(PMo<sub>12</sub>O<sub>40</sub>)(H<sub>2</sub>O)<sub>4</sub>]·3H<sub>2</sub>O (Co-PMo<sub>12</sub>), [Co<sup>II</sup><sub>1.5</sub>(L)<sub>1.5</sub>(PW<sub>12</sub>O<sub>40</sub>)(H<sub>2</sub>O)<sub>4</sub>]·3H<sub>2</sub>O (Co-PW<sub>12</sub>), [Co<sup>II</sup><sub>2</sub>(L)<sub>2</sub>-(SiW<sub>12</sub>O<sub>40</sub>)(H<sub>2</sub>O)<sub>4</sub>]·11H<sub>2</sub>O (Co-SiW<sub>12</sub>), and H[Co<sup>II</sup><sub>2.5</sub>(L)<sub>3</sub>-(P<sub>2</sub>W<sub>18</sub>O<sub>62</sub>)(H<sub>2</sub>O)<sub>8</sub>]·10H<sub>2</sub>O (Co-P<sub>2</sub>W<sub>18</sub>), which were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, and single crystal X-ray diffraction. The differences in catalytic activity among the four POMOCs for olefin epoxidation were attributed to the distinct accessibility of Co(II) sites upon thermal activation. Among them, Co-P<sub>2</sub>W<sub>18</sub> achieved a remarkable 99% yield of 1,2-epox-ycyclooctane within 3 h at room temperature using O<sub>2</sub> as the oxidant, owing to its highly accessible unsaturated Co(II) sites. Co-P<sub>2</sub>W<sub>18</sub> exhibits significantly superior catalytic activity for the cyclooctene epoxidation reaction compared to most reported catalysts. Additionally, the reaction mechanism was investigated using density functional theory.</p>

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Diverse polyoxometalate-based cobalt complexes for catalyzing olefin epoxidation reaction at room temperature: regulation of active sites by polyoxometalate templates

  • 期刊论文

  • 发表日期：

    2026年1月4日

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  • Zhixuan An,
  • Xiaohui Li,
  • Xuejiao Wang,
  • Chenlu Zhang,
  • Hui Li,
  • Xiuli Wang

摘要

Enhancing the catalytic activity of catalysts is a core objective in their design and synthesis processes, and the accessibility of active sites is one of the crucial factors determining catalyst activity. Polyoxometalate-based metal-organic complexes (POMOCs) with well-defined structures, which combine the advantages of POMs and MOCs, may offer the possibility to construct catalysts with highly accessible active sites. In this study, a series of POMOCs were successfully designed and synthesized using different POM templates, including [CoII1.5(L)1.5(PMo12O40)(H2O)4]·3H2O (Co-PMo12), [CoII1.5(L)1.5(PW12O40)(H2O)4]·3H2O (Co-PW12), [CoII2(L)2-(SiW12O40)(H2O)4]·11H2O (Co-SiW12), and H[CoII2.5(L)3-(P2W18O62)(H2O)8]·10H2O (Co-P2W18), which were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, and single crystal X-ray diffraction. The differences in catalytic activity among the four POMOCs for olefin epoxidation were attributed to the distinct accessibility of Co(II) sites upon thermal activation. Among them, Co-P2W18 achieved a remarkable 99% yield of 1,2-epox-ycyclooctane within 3 h at room temperature using O2 as the oxidant, owing to its highly accessible unsaturated Co(II) sites. Co-P2W18 exhibits significantly superior catalytic activity for the cyclooctene epoxidation reaction compared to most reported catalysts. Additionally, the reaction mechanism was investigated using density functional theory.