Construction of Polymer-Decorated Fe₃O₄@Catechol-formaldehyde Resin Amphiphilic Janus Nanospheres for Catalytic Applications

Janus particles are widely used as multifunctional materials for catalytic reactions due to their controllable asymmetry and stability efficiency of the interface structure. Herein, we propose a simple approach to design an amphiphilic “hairy” Janus nanocatalyst, which is composed of Fe3O4@catechol-formaldehyde resin (CFR) core–shell microspheres with different hydrophilic–hydrophobic polymer chains grafted on opposite sides of the microsphere and the catalytically active metal particles directly supported on the hydrophilic polymer chains. Amphiphilic Janus nanospheres (200–300 nm) with hydrophilic poly (N-isopropylacrylamide) (PNIPAM) and hydrophobic polystyrene (PSt) chains are synthesized by Pickering emulsion and mussel-inspired methods, followed by in situ reduction of Pd nanoparticles (Pd NPs) loaded onto the hydrophilic polymer chain side to form a Janus-structured Pd@PNIPAM-S-Fe3O4@CFR-S-PSt nanocatalyst. The amphiphilic Janus nanospheres have a good effect on the stability of the emulsion. Due to its special structural composition, the constructed Janus nanocatalyst exhibits excellent catalytic reduction performance for dyes and nitroaromatic compounds in both water and emulsion phases. Because of the existence of Fe3O4, the catalyst is easy to be separated and recovered, which augments the catalytic reaction cycle. In addition, the presence of temperature-sensitive PNIPAM polymer chains also enables the Janus nanocatalyst to display controllable temperature-responsive behaviors in stabilizing emulsions and emulsion catalysis. The as-prepared Janus nanomaterials with a variety of functions and properties possess potential for application in catalysis and biological and environmental areas.