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

Phase-transfer processes between immiscible liquids playa prominentpart in various applications, particularly for separation and recoveryof catalysts. Zeolitic-imidazolate frameworks (ZIFs), as a specificsubset of metal-organic frameworks, have been proven to beencouraging candidates for catalysts or cocatalysts because of theirappealing characteristics, whereas recovery and reusability of ZIFsstill remain a challenge because of their submicrometer-to-micrometersize. In this work, a kind of amino-modified ZIF-90 was designed andprepared, and by adjusting the hydrophobicity and hydrophilicity ofsurface species, these ZIFs could reversibly transfer between organicsolvents and water by alternate bubbling of CO2 and N-2. It was found that the mechanism of the phase transfer wasaroused from the reversible formation of hydrophilic salts upon CO2 addition. By employing this novel property of the functionalizedZIF-90, an efficient and regulable CuI-catalyzed cycloaddition wasfulfilled wherein the amino-modified ZIF-90 was applied to encapsulate,activate and reuse the catalyst, and regulate the reaction.