Solvent-Assisted Ligand Exchange of the 2D Zeolitic Imidazolate Framework (ZIF-L): Fine-Tuning the Facet Ligands for Anticorrosive Coatings

The cohybridization of metal-organic frameworks (MOFs), particularly zeolitic imidazolate framework-8 (ZIF-8), with two-dimensional (2D) nanomaterials has emerged as a promising approach to enhance both the barrier properties and active corrosion protection of epoxy (EP)-based coatings. However, the widespread use of these hybrid systems is hindered by environmental concerns associated with toxic methanol used in ZIF-8 synthesis, the limited accessibility of active sites, and the high production costs of 2D nanomaterials. Therefore, there is growing interest in developing alternatives that integrate the beneficial properties of MOFs and 2D materials while offering lower costs, greater environmental compatibility, and increased active site accessibility. Herein, a 2D leaflike zeolitic imidazolate framework (ZIF-L) was utilized as a low-cost, environmentally friendly alternative to ZIF-8 with dual functionality for active and barrier protection properties. The hydrophilicity of ZIF-L was fine-tuned through a facet ligand exchange with benzotriazole (BTA), which acted as both a surface modifier and a corrosion inhibitor. This solvent-assisted ligand exchange was validated by X-ray photoelectron spectroscopy (XPS) analysis. The BTA loading in BTA@ZIF-L was determined to be 14.43 wt %. Incorporating 1 wt % BTA@ZIF-L pigment into the EP matrix resulted in a higher cross-linking density compared to both blank/EP and ZIF-L/EP coatings, yielding ultrahigh impedance values (∼1011 Ω cm2) at the lowest frequency, even after 4.5 months of immersion in a 3.5 wt % NaCl solution. Additionally, the active corrosion inhibition capability of the BTA@ZIF-L/EP coating was demonstrated through electrochemical impedance spectroscopy (EIS) analysis of scratched coatings, showing a 130% increase in the total resistance relative to blank/EP, which was further validated by salt spray testing.