Nanoconfinement-tuned polyaniline in hierarchically porous MOF network for efficient corrosion resistance

The encapsulation environment of polymers affects their physicochemical properties. Existing polymer-based anticorrosion nanofillers are often plagued by poor dispersibility and designability. The studies concerning the intrinsic correlation between polymer modulation and anticorrosion performance remain rare. Herein, we developed a series of anticorrosion composite nanofillers by encapsulating polyaniline (PANI) within hierarchically porous Zr-based metal-organic framework (UiO-66-NH 2 -X, denoted as U6N-X) networks with tunable mesopore sizes (3.5–7.7 nm) through in-situ polymerization of aniline monomers. Tuning pore sizes of the networks enabled the regulation of the PANI encapsulation environment. Benefiting from the spatial confinement effect of the U6N-X support, PANI encapsulated in a confined environment not only exhibits favorable dispersibility but also enhances electron transfer capability and exposes abundant active sites. Density functional theory (DFT) calculations further reveal that confined encapsulation narrows the energy gap of PANI and selectively improves its redox capability. This facilitates electron migration during the formation of passivation products and provides durable protection for the steel substrate. The composite epoxy coating prepared with screened PANI@U6N-18 filler, which possesses the lowest electron transfer resistance and the highest electrochemically active area, exhibits superior passivation protection ability. After 20-day simulated seawater immersion, no apparent rust is observed on the artificially scratched PANI@U6N-18/EP coating. Moreover, the low-frequency impedance modulus of the PANI@U6N-18/EP remains 8.29 × 10 10 Ω·cm 2 after 70 days of prolonged immersion, reaching about 30 times higher than that of the composite epoxy coating filled with pristine PANI.