Sustainable pH-Responsive Ce–Tb–BTC@PDA Composite for Smart Coatings with Dual Functionality: Corrosion Reporting and Active Protection

The development of sustainable corrosion protection systems that combine real-time damage sensing with autonomous repair remains a significant challenge. Herein, we present an eco-friendly smart composite coating integrating pH-responsive polydopamine with a Ce-Tb bimetallic metal-organic framework (MOF), forming a multifunctional system through innovative metal-ligand coordination chemistry. This synergistic composite design enables two complementary mechanisms: (1) Reversible Ce3+-benzene-1,3,5-tricarboxylic acid (BTC) coordination facilitates autonomous self-healing via acid-triggered metal release and protective barrier formation at defects; (2) Simultaneously, Tb3+ fluorescence probes provide rapid (<5 min) corrosion visualization through pH/Fe3+-responsive quenching. Crucially, Ce3+ acts dually as a structural repair agent and a fluorescence sensitizer, enhancing the Tb3+ emission intensity and pH sensitivity via efficient energy transfer. By strategically utilizing abundant Ce3+ to minimize scarce Tb3+ consumption, the composite achieves superior resource sustainability without compromising functionality. Electrochemical characterization confirms the outstanding performance: Intact coatings exhibit a low-frequency impedance modulus |Z|0.01 Hz of 1.90 × 107 Ω·cm2, ∼5 times higher than conventional epoxy coatings. Even scratched samples maintain an impedance 2.8 times higher (3.65 × 104 Ω·cm2) than controls after 120 h immersion, demonstrating robust self-repair. This work establishes a blueprint for next-generation multifunctional protective composites utilizing sustainable metal coordination chemistry.