A pH-responsive TiO2-based Pickering emulsion system for in situ catalyst recycling

Developing methods for efficient product/catalyst separation and catalyst recycling is meaningful in multi-phase catalytic reactions. Here, we reported a pH-responsive emulsion system stabilized by interfacially active TiO₂ nanoparticles for achieving in situ product/catalyst separation and catalyst recycling. In this system, emulsification and demulsification process could be easily engineered through tuning the pH values. The emulsion droplets were destroyed completely at a pH value of 3–4, and the solid catalyst distributed in the aqueous phase could be used to the next reaction cycle after removal of the organic product and adjusting the pH to 7–8. Such a pH triggered switchable Pickering emulsion catalytic system not only shows good recyclability of the solid catalyst but also high catalytic efficiency, and could be recycled more than 10 cycles.