Redox-switchable Pickering emulsion stabilized by hexaniobate-based ionic liquid for oxidation catalysis.

Pickering emulsions provide an efficient platform for interfacial catalysis, but product separation and catalyst recycling rely on time- and energy-consuming centrifugation or filtration. Herein, three hexaniobate-based ionic liquids, [C n MIM]Nb 6 ( n = 12, 14 and 16), have been successfully synthesized by self-assembly of hexaniobate (Nb 6 ) with long alkyl chain-modified imidazole cations (C n MIM). Interestingly, the surface wettability of [C 16 MIM]Nb 6 can be regulated by redox reactions, and the rapid switch between emulsification and demulsification can be achieved by alternately adding oxidant (H 2 O 2 ) and reductant (Na 2 SO 3 ) agents. Furthermore, studies suggest that the redox-responsive behavior is related to the reversible transformation between [C 16 MIM]Nb 6 and peroxohexaniobate [C 16 MIM]Nb 6 -O 2 , which leads to the rearrangement of hydrophobic long chains on imidazole cations around hydrophilic Nb 6 . Moreover, [C 16 MIM]Nb 6 can effectively catalyze oxidative desulfurization (conversion > 99%), and the separation of clean model oil and the recycling of the interfacial catalyst were realized in a facile route.