Ligand-exchange-driven in situ conversion of deleterious bronze rust into a functional metal-organic frameworks-based superhydrophobic shield

This study presents a ligand-exchange-driven strategy for the in situ conversion of bronze patina into functional Cu-BTC metal–organic frameworks (MOFs), thereby transforming deleterious corrosion products into a protective superhydrophobic barrier. By leveraging the coordination affinity of trimesic acid (BTC), Cu 2+ ions within the harmful rust layer undergo ligand exchange to nucleate an in situ Cu-BTC MOF layer. It was found that the deprotonation degree of BTC, regulated by NaOH, enabled the precise tailoring of the film from octahedra to high-roughness 2D nano-flowers. Following secondary modification with stearic acid (SA), the resulting dual-phase hybrid film achieved exceptional superhydrophobicity with a static water contact angle of 158.5°. Beyond physical shielding, high-resolution XPS, EDS mapping and theoretical calculation corroborated that this process facilitated the chemical conversion and deep-seated sequestration of active Cl − ions. Electrochemical impedance spectroscopy revealed a superior corrosion inhibition efficiency of 99.9%, primarily attributed to a stable interfacial “air plastron”. Failure analysis indicated a graded degradation pathway: even after localized hydrolysis of the MOF phase, the chemically robust Cu-SA component provided critical residual protection. By achieving “chemical cleaning” of the rust through ligand exchange, this research offers a non-destructive and sustainable method for in situ preservation of patinated metallic heritage.