This work demonstrated that the specific ionic liquids (ILs) have been designed via the supramolecular complexation between 18-crown-6 (CE) and ammonium peroxoniobate (NH₄-Nb). The resultant ILs have been characterized by elemental analysis, FT-IR, Raman, NMR, DSC, conductivity measurement and MALDI-TOF, etc. The IL (CE-1) consisting of CE and ammonium peroxoniobate can be further coordinated with GLY to generate a new IL (CE-2), which showed both high catalytic activity in epoxidation with H₂O₂ and good recyclability. The characterization of ⁹³Nb NMR spectra revealed that the peroxoniobate anions has demonstrated a structural evolution in the presence of hydrogen peroxide, in which NbO species can be easily oxidized into the catalytically active niobium−peroxo species. Especially, the supramolecular complexation can provide suitable hydrophobicity, which ensured that the hydrophobic olefins and allylic alcohols were easily accessible to the catalytically active anions, and thus facilitated the epoxidation reaction. Notably, the supramolecular IL catalysts in this work exhibited a huge advantage of the easy availability, as compared with the previously reported peroxoniobate-based ILs. As far as we know, this is the first example of the highly selective epoxidation of olefins and allylic alcohols by using supramolecular ILs as catalysts.

这项工作表明，特定的离子液体（ILs）是通过18冠6（CE）和过氧苯甲酸铵（NH ₄ -Nb）之间的超分子络合设计的。通过元素分析，FT-IR，拉曼，NMR，DSC，电导率测量和MALDI-TOF等对所得的IL进行了表征。由CE和过氧铌酸铵组成的IL（CE-1）可进一步与GLY配合生成一种新的IL（CE-2），它在H ₂ O _2的环氧化中显示出高催化活性，并具有良好的可回收性。⁹³ Nb NMR光谱的表征表明，过氧铌酸根阴离子在过氧化氢存在下显示出结构演化，其中NbO物种很容易被氧化成具有催化活性的铌-过氧物种。特别地，超分子络合可以提供合适的疏水性，这确保了疏水性烯烃和烯丙基醇易于被催化活性阴离子接近，并因此促进了环氧化反应。值得注意的是，与先前报道的基于过氧异氰酸酯的ILs相比，这项工作中的超分子IL催化剂具有易于获得的巨大优势。据我们所知，这是通过使用超分子IL作为催化剂对烯烃和烯丙醇进行高选择性环氧化的第一个例子。