Stimulus-responsive Pickering emulsion droplet-based microreactors for green biphasic catalysis.

Area of Science:

• Biphasic catalysis
• Emulsion science
• Nanomaterials

Background:

• Pickering emulsions (PEs) are promising for biphasic catalysis but face challenges like reactant diffusion, particle leaching, and difficult catalyst recovery.
• Existing nanoparticle-stabilized PEs have limitations hindering their practical application in catalysis.

Purpose of the Study:

• To develop a general approach for designing a Pickering emulsion droplet-based reactor.
• To overcome the limitations of traditional nanoparticle-stabilized PEs using nanogel particles and switchable surfactants.
• To demonstrate the efficacy of the developed reactor in organic synthesis.

Main Methods:

• Utilized egg white nanogel particles (EWNGs) at 0.01 wt.% for stabilization.
• Employed a newly synthesized switchable surfactant, 3-(10-carboxydecyl)-1-methyl-1H-imidazolium bromide (ImDec-COOH), at 0.50 wt.%.
• Designed a Pickering emulsion droplet-based reactor.

Main Results:

• The nanogel-stabilized PE system overcame limitations such as reactant diffusion and incompatible reaction environments.
• Stimulus-responsive surfactants adjusted the pH of the PE systems.
• The reactor facilitated organic transformations through biphasic catalysis with high yields.
• Achieved in situ product separation and excellent catalyst recovery in the synthesis of benzothiazoles and benzoxazole.

Conclusions:

• Developed a versatile Pickering emulsion reactor using egg white nanogel particles and a switchable surfactant.
• The system offers an efficient and sustainable platform for biphasic catalysis, addressing key limitations of previous methods.
• Demonstrated successful application in the one-pot synthesis of valuable heterocyclic compounds with high efficiency and recoverability.