Highly efficient and recyclable acid catalysis using high-temperature resistant O/W emulsion stabilized by dodecyl phosphonic acid†

Acid-catalyzed reactions play an important role in the field of organic synthesis in synthesizing a large number of organic compounds. However, conventional acid catalysts have many shortcomings, such as low stability, difficulty in product separation and poor reusability. In this study, we achieved efficient and recyclable acid catalysis via a pH-responsive O/W emulsion system stabilized by dodecyl phosphonic acid (DPA) alone. The O/W emulsion exhibited excellent characteristics of high-temperature resistance and adjustable oil-droplet size at different temperatures. Moreover, the emulsion state can undergo rapid and reversible transitions between emulsification and demulsification by adjusting the pH levels. Impressively, the emulsified acid-catalysis system significantly enhanced the reaction efficiency of the Knoevenagel condensation reaction. Subsequently, a straightforward pH adjustment effortlessly realized product separation and ensured the recyclability of the catalytic system. This environmentally friendly and economically viable system offers a new approach to achieve efficient and green catalysis in organic synthesis processes.