Enhanced catalytic degradation performance of azo dyes based on Janus emulsification

Amphiphilic Janus nanosheets with an asymmetric structure of non-polar phenyl side and polar ionic liquid side (1-Butyl-3-methylimidazolium chloride, [BMIM]Cl), denoted as Janus-[BMIM]Cl, were prepared and used as a carrier to achieve the integration of catalyst and emulsifier. Catalytic heteropolyanions (e.g., [PW12O40]3-, [PMo12O40]3- or [SiW12O40]4-) were selectively decorated on the polar side induced by anion-exchange of [BMIM]Cl moieties, Janus catalysts (Janus-[BMIM][heteropolyanions]) were assembled and utilized as an open degradation platform for azo dyes such as methyl orange (MO). Morphology, structure, and properties were characterized by SEM, FT-IR, XPS, UV-Vis, Zeta potential, etc. The inbuilt amphipathy of Janus nanosheets endowed the decolorization process of dyes to perform in the emulsified system. The extremely increased interface coupled with the effective dispersion of catalysts at the interface synergistically improved the catalytic degradation performance. Compared with the decolorization catalyzed in a conventional immiscible system, the removal efficiency of MO achieved in the Janus emulsion greatly improved from 78.6 to 98.2% within 3 h. Besides, the Janus emulsion could be demulsified easily by centrifugation, and the degradation efficiency was still maintained at 93.7% after five cycles. These results provide valuable information for exploring and enriching the applications of Janus functional materials.