查找使用阿拉丁产品的科研文献

Boosting H2O2 Activation for the Efficient Alkene Epoxidation over Polyoxometalate-based Tetrakaidecahedron-like Nanodice Assemblies

Yali Zhao,Ziru Wang,Jinxiu Zhai,Xingjian Cao,Peilei He

Graphical The lacunary polyoxometalate ([PW 11 O 39 ] 7− , PW 11 ) can self-assemble with TBAB to form tetrakaidecahedron-like nanodices (NDs). These NDs exhibit significantly higher catalytic activity for the epoxidation of cyclooctene compared to PW 11 alone and nanospheres (NSs) formed from the non-lacunary polyoxometalate ([PW 12 O 40 ] 3− , PW 12 ). DFT studies confirm the critical role of hydroperoxo species generated at the lacunary site in facilitating oxygen transfer to cycloalkenes over PW 11 . The activation of hydrogen peroxide (H 2 O 2 ) as a terminal oxidant holds great promise for catalytic oxidation processes. However, developing an efficient catalyst for the epoxidation of bulky organic molecules with H 2 O 2 , including cyclic alkenes, remains challenging. In this research, a lacunary polyoxometalate (POM)-based tetrakaidecahedron nanodices (NDs) are synthesized by [PW 11 O 39 ] 7− (PW 11 ) clusters with tetrabutylammonium bromide (TBAB). The NDs exhibit significantly enhanced catalytic activity in the epoxidation of cyclooctene, with a yield 55.4 times greater than that of the raw PW 11 . Conversely, nanospheres (NSs) assembled from non-lacunary POM clusters of [PW 12 O 40 ] 3− (PW 12 ) under the same conditions achieve only a 2.9 % yield, highlighting the essential role of the lacunary PW 11 structure in NDs. Raman spectroscopy and density functional theory (DFT) calculations confirm that the active hydroperoxo species from H 2 O 2 activation serves as the effective epoxidizing agent. The reduced energy barrier for H 2 O 2 activation on PW 11 , relative to PW 12 , corroborates the superior activity of the NDs. Furthermore, the intermediate generated post-H 2 O 2 activation shows stronger adsorption of cyclooctene, increasing oxygen transfer to cyclooctene during the epoxidation process. This study demonstrates the exceptional performance of an assembly structure utilizing lacunary POMs for the activation of H 2 O 2 and subsequent oxidation reactions.