Aqueous-System-Enabled Spray-Drying Technique for the Synthesis of Hollow Polycrystalline ZIF-8 MOF Particles

Zeolitic imidazolate framework-8 shares the same topology with sodalite zeolite but consists of Zn nodes bridged by imidazolate linkers to form a neutral open-framework structure. ZIF-8 has been recognized as a unique molecular sieving material with a flexible framework enabling interesting “gate-opening” functionality. Controlling the crystal size and shape is crucial for regulating the structural flexibilities and mass transport properties. The present study demonstrates that an aqueous-system-enabled spray-drying process enables the shape engineering of ZIF-8 with a hollow polycrystalline structure. It is notable that our synthesis route produces an amorphous zinc complex compound, which possesses a continuous random network partially with crystalline fillers, after spray drying followed by an amorphous-to-crystal transition via activation treatment using polar organic solvents. The size of primary ZIF-8 crystals consisting of secondary polycrystals depends on the kind of the organic solvent. The macro...