Dynamic interfacial catalysis via pH-tunable Ni-decorated carbon dot pickering emulsions for enhanced reaction efficiency

This study presents a novel responsive carbon dot-based surfactant system that exhibits catalytic activity at the interface of an oil-in-water Pickering emulsion microreactor containing reactants. Nickel nitrate was employed to dope carbon dots via a microwave-assisted method, imparting catalytic functionality to the resulting nanomaterials. Subsequently, poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) was grafted onto the surface of the nickel-doped carbon dots through electron transfer radical polymerization, yielding the catalytically responsive solid emulsifier Ni@CD-NH-Met-PDMAEMA (Ni@CD-3). Owing to the metal doping of carbon dots and subsequent emulsification functionalization, Ni@CD-3 demonstrates exceptional ability to stabilize reactive droplets in Pickering emulsion while exhibiting intrinsic catalytic activity at the oil–water interface. Notably, Ni@CD-3 exhibits high catalytic activity, with an extremely short reduction reaction time required to achieve a conversion efficiency exceeding 99%, attributed to the advantageous interfacial properties of the emulsion. Its catalytic efficiency is 560% higher than that of Fe@CD-3 under comparable conditions. Furthermore, the cyclic response property of Ni@CD-3 enables in situ separation and emulsion-breaking recovery by adjusting the pH at the end of the reaction. This property facilitates the recovery and reuse of the catalyst for up to five cycles, with the catalytic efficiency maintained above 99% for the first three cycles. These results suggest that the Ni@CD-3-based emulsion microreactor system holds great promise as a high-performance catalyst for diverse organic chemical reactions.