Important Progress in the Study of Sub-nanostructured Catalysts for Magnetic MOF Pore-confined Ionic Liquids

Aryl-oxazolidinones are nitrogen heterocyclic compounds with biological activity. These compounds find extensive applications in pharmaceuticals, pesticides, and antibacterial and herbicidal applications. Due to their versatile nature and potential therapeutic properties, aryl-oxazolidinones continue to attract attention in drug discovery, agrochemical development, and related industries. Homogeneous ionic liquid catalysts with multiple active sites show good catalytic effects, but the active components are easily lost and cannot be recycled for a long time, which are not easy to separate. To make full play of the multifunctionality and high activity of homogeneous ionic liquid catalysts, meanwhile to realize the efficient separation and recycling is the bottleneck problem that needs to be solved for the industrialization of the catalysts.

Recently, the Green Catalytic Materials and Process Technology research team in the School of Chemical Engineering, in collaboration with researchers from Qinghai Salt Lake Research Institute, Chinese Academy of Sciences, developed a magnetic MOF pore-confined ionic liquid sub-nanostructured catalyst. Firstly, Fe₃O₄ with a SiO₂ capping layer was modified with sodium polystyrene sulfonate (PSS), and a Fe₃O₄@MOF material (MAG-UiO-66) was constructed on the Fe3O4-PSS outer layer to enable magnetic separation. Subsequently, the 1-butyl-3-methylimidazole bromide salt ([C₄mim] [OAc]) ionic liquid was pore-confined into the MAG-UiO-66 sub-nanometer space and self-assembled as a highly active, easily recoverable, and recyclable magnetic MOF-confined catalyst, MAG-UiO-66-IL(OAc), with the design idea shown in Figure 1.

Fig. 1. Design of the magnetic pore-confined catalyst MAG-UiO-66-IL(OAc)

In the catalytic performance test for the synthesis of aryl oxazolidinones from aryl amines and cyclic carbonates, the catalyst was used to obtain aryl oxazolidinones in high yields of 95%. The stability and reusability of the catalyst were significantly improved over the traditional "anchored" and "grafted" MOF-supported catalysts. The catalyst can be easily recovered with a magnet, and the yield can still reach more than 90% after 10 times of reuse, as shown in Fig. 2 for the catalyst activity and reusability test.

Fig. 2. The magnetic pore-confined catalyst: catalytic activity and reusability tests

The experimental data showed that the synthesized magnetic pore-confined catalyst MAG-UiO-66-IL(OAc) still maintained the crystal structure of UIO-66, and the ionic liquid [C4mim] [OAc] was successfully self-assembled and confined into the magnetic carrier MAG-UIO-66. In addition, the proposed reaction mechanism was further supported by quantum chemical calculations and ancillary experimental studies. Some characterization data of the catalysts are shown in Fig. 3

Fig. 3. Schematic diagram of partial characterization data of the magnetic pore-confined catalyst

The results were published in the Chemical Engineering Journal (IF=15.1, Chinese Academy of Sciences Q1) with the title "A magnetic pore-confined catalyst with ionic liquids supported on MOFs for the synthesis of aryl-oxazolidinones: design, performance, and recyclability". Siying Chong and Jiaoyan Li from Shenyang University of Chemical Technology were the first authors of this study, while Prof. Kangjun Wang, Prof. Yajing Zhang from Shenyang University of Chemical Technology, and Ruirui Liu from Qinghai Salt Lake Research Institute, Chinese Academy of Sciences were the corresponding authors, Shuang Zhao and Gangwei Huang participated in this study.

Chong S Y, Li J Y, Wang K J, et al. A magnetic pore-confined catalyst with ionic liquids supported on MOFs for the synthesis of aryl-oxazolidinones: design, performance, and recyclability[J]. Chemical Engineering Journal, 2024, 481, 148678.

DOI: 10.1016/j.cej.2024.148678

https://doi.org/10.1016/j.cej.2024.148678