Alcohols selective oxidation with H2O2 catalyzed by robust heteropolyanions intercalated in ionic liquid-functionalized graphene oxide

A set of heteropolyacid-based ionic heterogeneous catalysts (PW@IL-GO(m)) have been synthesized by intercalated heteropolyanions in ionic liquid (IL)-functionalized graphene oxide (GO) via amino-protonation and/or anion-exchange reaction. This immobilization method offered improved dispersity, accessibility and stability of active sites. The amphipathic nature of IL-GO sheets and porosity of PW@IL-GO(m) are beneficial to reducing mass transfer limitation in a water/organic substrate two-phase system. Then, these obtained hybrids were employed as efficient and robust catalysts for the selective oxidation of alcohols into carbonyl compounds using hydrogen peroxide as an oxidant under organic solvent-free condition. As expected, PW@IL-GO(m) catalysts showed even much better activity than the corresponding homogeneous HPW (phosphotungstic acid) catalyst. Particularly, PW@IL-GO(1.5) gave a benzyl alcohol conversion of 94% and benzaldehyde chemoselectivity of 91%. Moreover, owing to the heterogeneous nature and strong cation-anion interactions between cationic supporter and PW anions, the as-prepared catalyst presented advantages of convenient recovery, simple preparation and steady reuse, further providing the industrial application potential in sustainable oxidation reactions.