Supercritical Carbon Dioxide Enables Rapid, Clean, and Scalable Conversion of a Metal Oxide into Zeolitic Metal–Organic Frameworks

Supercritical carbon dioxide (CO2) is an established medium for synthesizing molecular compounds and activation of microporous solids, but is much less explored for transformations of high-melting ionic reactants, such as metal oxides. We show that supercritical CO2 enables direct, clean, and rapid transformation of zinc oxide into zeolitic imidazolate frameworks (ZIFs), without requiring toxic or corrosive metal nitrate or chloride precursors, organic or aqueous solvents, additives, or auxiliaries. While recent syntheses of coordination polymers and metal–organic frameworks from supercritical CO2 highlighted the need for specialized metal reagents designed for solubility, we unexpectedly find that ZnO is quantitatively converted into grams of diverse ZIFs in minutes, with hundred grams of popular ZIF-8 accessible within an hour.