Environment-Friendly Heterogeneous Poly(Ionic Liquid)S Immobilized Polyoxometalate Catalysts Towards the Efficient Oxidation of Alkenes

Abstract

A novel quaternization reagent of (1E,1'E)-1,1'-(1,4-phenylene)bis(N-(3-(1H-imidazol-1-yl)propyl)methanimine) (PP) was synthesized and used for the preparation of a series of poly(ionic liquid)s (PILs) via the quaternization reaction. These PILs were subsequently loaded with polyoxometalates (POMs) to create innovative catalysts for the oxidation of alkenes. Comprehensive structural analysis of the catalysts showed that these PILs exhibited a high loading amount ratio of up to 542% for POMs, which were well-dispersed on the surface of PILs. The PILs loaded POMs catalysts, especially for PW-PIL-TB-2PP with H3PW12O40 as the POMs, displayed remarkable activity and stability in oxidizing cyclooctene, achieving a conversion rate of 97% and a selectivity of 99% for 1,2-epoxycyclooctane over six consecutive runs without notable loss. Furthermore, the PW-PIL-TB-2PP catalyst could also be used for the oxidation of a wide range of cyclic, linear, and aromatic alkenes.

Keywords: quaternization reaction, poly(ionic liquid)s, polyoxometalates, alkenes, oxidation