A phosphomolybdic acid (PMA)-based heterogeneous catalyst, denoted as PMA/KAP, was prepared by immobilizing PMA onto a knitting aryl network polymer (KAP) based on triphenylphosphine (PPh₃). The catalytic property of PMA/KAP was investigated for the selective oxidation of olefins with aqueous hydrogen peroxide (H₂O₂) as oxidant. When using ethyl acetate (EAC) as reaction medium, PMA/KAP performs higher activity and selectivity to epoxide for a variety of olefins, and it can be reused for several times without obvious loss of activity. When the reaction was carried out in acetonitrile (AN) medium, deactivation of PMA/KAP catalyst can be observed immediately. A variety of characterization results suggest that the degradation of PMA unit to (PO₄[MoO(O₂)₂]₄)³⁻ occurs easily when the PMA/KAP catalyst is operated in H₂O₂/AN system, while such degradation behavior could be significantly inhibited when the catalyst is used in the system of H₂O₂/EAC. We proposed that the neighbouring P-containing ligands dispersed in the framework of KAP can produce a steric pocket with low electron density, which can promote the formation of multi-weak coordination interaction between PMA unit and several P ligands. Such multi-weak interaction can inhibit the degradation of PMA to (PO₄[MoO(O₂)₂]₄)³⁻, thus avoiding the leaching of active species from the KAP support, and resulting in the formation of relatively stable heterogeneous PMA supported catalyst for olefin epoxidation with H₂O₂ in the media of EAC.

中文翻译：

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磷钼酸官能化的编织芳基网络聚合物上的过氧化氢水溶液对烯烃的选择性氧化

通过将PMA固定在基于三苯基膦（PPh ₃）的针织芳基网络聚合物（KAP）上，制备了基于磷钼酸（PMA）的多相催化剂，称为PMA / KAP 。研究了PMA / KAP在以过氧化氢水溶液（H ₂ O ₂）为氧化剂的条件下烯烃选择性氧化的催化性能。当使用乙酸乙酯（EAC）作为反应介质时，PMA / KAP对多种烯烃具有更高的活性和对环氧化物的选择性，并且可以重复使用数次而不会明显降低活性。当反应在乙腈（AN）介质中进行时，可以立即观察到PMA / KAP催化剂失活。各种表征结果表明PMA单元降解为（PO ₄当在H ₂ O ₂ / AN系统中操作PMA / KAP催化剂时，[MoO（O ₂）₂ ] ₄）^3-容易发生，而当在H ₂系统中使用催化剂时，这种降解行为会被明显抑制。O ₂ / EAC。我们提出，分散在KAP骨架中的相邻含P配体可以产生一个具有低电子密度的空间袋，这可以促进PMA单元与几个P配体之间的多弱配位相互作用的形成。这种多弱相互作用可以抑制PMA降解为（PO ₄ [MoO（O ₂）₂ ] ₄）^3-，从而避免了活性物质从KAP载体中浸出，并导致在EAC介质中形成相对稳定的多相PMA负载催化剂，用于H ₂ O ₂进行烯烃环氧化。