Sequential Release From Hierarchical MOF‐on‐MOF Architectures for Programmable Self‐Healing and Self‐Warning Coatings

ABSTRACT

Stimuli‐responsive micro/nanocontainers play a vital role in targeted delivery for protective coatings. Achieving precise functions necessitates a new generation of materials capable of stepwise‐controlled release of multiple payloads. However, co‐encapsulating diverse active agents poses challenges, particularly in achieving sequential release, critical for advancing complex protective strategies. Herein, hierarchical MOF‐on‐MOF core–shell containers were constructed by mild epitaxial growth to spatially accommodate corrosion inhibitors and warning agents. The ZIF‐67@ZIF‐8 system showed a two‐stage release profile, with preferential MBT release from the less stable ZIF‐67 core followed by delayed BTA release from the ZIF‐8 shell. Comparatively, the parallel ZIF‐8@ZIF‐8 architecture exhibited largely overlapped release profiles. This observation suggests that core–shell construction alone does not guarantee staged release and that framework stability contrast is an important factor in regulating temporal delivery. When incorporated into epoxy coatings, the inhibitor‐loaded containers enhanced defect‐site corrosion protection on Cu and Al substrates, while Phen‐containing containers enabled colorimetric warning on Fe‐based substrates. This work demonstrates a stability‐gradient strategy for temporally programmed delivery in multifunctional corrosion‐protective coatings.