CO₂-Induced Phase Transfer of Amino-Modified ZIF-90 between Immiscible Liquid Phases for Recyclable Efficient Synergistic Catalysis

Phase-transfer processes between immiscible liquids play a prominent part in various applications, particularly for separation and recovery of catalysts. Zeolitic-imidazolate frameworks (ZIFs), as a specific subset of metal–organic frameworks, have been proven to be encouraging candidates for catalysts or cocatalysts because of their appealing characteristics, whereas recovery and reusability of ZIFs still remain a challenge because of their submicrometer-to-micrometer size. In this work, a kind of amino-modified ZIF-90 was designed and prepared, and by adjusting the hydrophobicity and hydrophilicity of surface species, these ZIFs could reversibly transfer between organic solvents and water by alternate bubbling of CO 2 and N 2 . It was found that the mechanism of the phase transfer was aroused from the reversible formation of hydrophilic salts upon CO 2 addition. By employing this novel property of the functionalized ZIF-90, an efficient and regulable CuI-catalyzed cycloaddition was fulfilled wherein the amino-modified ZIF-90 was applied to encapsulate, activate and reuse the catalyst, and regulate the reaction.