High-Precision Assembly of Molecularly Thin Zeolite Nanosheets into Tiled Mono- and Multilayer Films for Robust Corrosion Protection

The fabrication of zeolite films by conventional hydrothermal methods limits their practical use because it produces irregular, nonuniform thick coatings under harsh synthesis conditions. In this study, to address these limitations, MCM-56 and bifer nanosheets exfoliated from their precursor layered zeolites were employed, and solution-based deposition methods were examined to prepare compact nanoscale-thick monolayer films of neatly tiled nanosheets under mild conditions. Atomic force microscopy revealed that spin coating, the pick-up method, and the Langmuir–Blodgett technique yielded high-quality monolayer films with predominantly monolayer coverage of >80% and low surface roughness (<1 nm), in contrast to the previously reported electrostatic adsorption method, which produced rough and uneven films. By repeating the deposition of monolayer films using the pick-up method, multilayer zeolite films were also successfully constructed. Their well-ordered stacked structure was confirmed by the progressive enhancement of the FT-IR band corresponding to Si–O–Si of the zeolite upon repeated deposition of monolayer films, as well as by the sharp X-ray diffraction peaks derived from the multilayer structure. The multilayer films were further deposited on a copper substrate, and their corrosion resistance was examined. As a result, the corrosion current density decreased by nearly an order of magnitude, and the corrosion potential shifted toward more positive values. These results indicate that highly ordered zeolite films exhibit pronounced anticorrosion effects while being deposited to a thickness of only tens of nanometers under mild conditions. These findings provide a general strategy for constructing highly ordered ultrathin zeolite films and expand the potential of zeolite nanosheets for functional surface coatings.