Fabrication of well-intergrown ZIF-8 films via sequential ZnO seed layer overlaying

The fabrication of well-intergrown metal–organic frameworks (MOFs) in film morphology is crucial for various applications such as gas separation and sensing, as it necessitates uniform and controlled mass transport and sorption at the internal pore surfaces. In this work, we report the growth of continuous zeolitic imidazolate framework-8 (ZIF-8) thin films via a secondary solvothermal growth method using a consecutive ZnO seed layer overlaying approach. The primary growth of ZIF-8 crystals on planar substrates occurs through heterogeneous nucleation in solution, followed by overlaying ZnO seed layers via radio frequency (RF) sputtering for secondary growth. We systematically investigate the morphology, crystallinity, and surface properties of the resulting ZIF-8 films. Our results confirm that the seed layer overlaying induces core–shell-like growth on the primary ZIF-8 crystals, promoting conformal growth and interconnection between isolated islands. These findings demonstrate a promising method for synthesizing continuous, well-intergrown MOF films with high surface coverage with various compositions and porosities for numerous applications.