The increasing accumulation of polyethylene terephthalate (PET) textile waste and the continued reliance on fluorinated (PFAS-based) water-repellent coatings represent two pressing environmental concerns. Herein, we report a sustainable waste-to-value strategy that simultaneously addresses these challenges by converting discarded colored PET textiles into high-performance, PFAS-free metal–organic framework (MOF) hybrid composites for durable superhydrophobic and anti-fouling coatings. Waste polyester fabrics were chemically depolymerized to recover terephthalic acid (H₂BDC) organic linkers, with efficient dye removal to minimize secondary water pollution. The extracted linkers were subsequently used to synthesize UiO-66(Zr) MOFs, yielding different crystal morphologies depending on the colored PET textile source. Fourier transform infrared (FTIR) and Raman spectroscopy confirmed the successful purification of H₂BDC and the formation of high-quality MOFs. At the same time, X-ray diffraction (XRD) verified the crystalline integrity of UiO-66 comparable to commercial materials.
The recycled PET-derived UiO-66 was combined with SiO₂ nanoparticles to construct transparent, hierarchically structured hybrid coatings. These coatings were successfully applied to a range of substrates, including various textile fabrics (e.g., cotton and blended textiles) and air filter membranes, demonstrating broad substrate compatibility. The latter is particularly important for air filtration applications, where moisture accumulation can degrade filtration efficiency. Atomic force microscopy (AFM) revealed a systematic increase in surface roughness with increasing SiO₂ content, indicating the formation of micro- and nano-scale hierarchical textures. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) showed uniform coating coverage and homogeneous elemental distributions of Zr, Si, C, and O across all substrates. X-ray photoelectron spectroscopy (XPS) further confirmed strong interfacial bonding via Zr–O coordination between UiO-66 and surface hydroxyl groups, ensuring robust coating on both fibrous textiles and polymeric filter membranes.
Surface wettability was evaluated using static water contact angle (WCA) and contact angle hysteresis (CAH) measurements. Pristine cotton fabric exhibited a hydrophilic WCA of 37.7°, whereas UiO-66 modification (UF-0) converted the surface into a water-repellent state with a WCA of 149.6°. With increasing SiO₂ loading, the WCA increased to 153.7° (UF-10), 158.3° (UF-20), and 160.4° (UF-30), confirming the establishment of a superhydrophobic state. The incremental WCA gain decreased at higher SiO₂ contents, indicating saturation and diminishing returns beyond moderate nanoparticle loading. CAH measurements showed that UF-0 exhibited the lowest hysteresis (31.7°), indicating enhanced droplet mobility and reduced contact-line pinning. Higher SiO₂ loadings increased CAH up to 46.0° (UF-30), reflecting increased surface roughness beneficial for anti-fouling and self-cleaning performance.
Importantly, the coatings retained high WCA, droplet repellency, and self-cleaning behavior after repeated washing cycles and under humid conditions, confirming their durability and suitability for practical use. Overall, this work demonstrates a circular and environmentally benign route for transforming waste PET textiles into versatile MOF-based superhydrophobic coatings, enabling PFAS-free water repellency and humidity-resistant surfaces for textiles and air filtration membranes.