Acetic acid vapours adsorption-induced morphological change in FeBTC metal–organic framework

• Acetic acid uptake of FeBTC outperformed that of common adsorbents used in conservation. • High uptake: 0.87 ± 0.09 mg·mg⁻ 1 AcOH at 237 h. • Two‑step adsorption kinetics best described by a double‑exponential model. • AcOH vapour induces morphology change of FeBTC from blocky particles to hollow cylinders. • Acetic acid vapour adsorption led to a surface area change. We report a post‐synthetic vapour phase modulation strategy to tailor the morphology of semicrystalline FeBTC metal–organic frameworks (MOFs) via acetic acid (AcOH) vapours adsorption. FeBTC, synthesized through a green one‐pot route, retained its crystalline structure upon exposure to AcOH vapours, as confirmed by WAXS. Adsorption kinetics followed a double‐exponential model, reaching 0.87 ± 0.09 mg·mg⁻ 1 uptake at 237 h. µFTIR spectroscopy demonstrated a uniform distribution of AcOH on FeBTC surface, whereas thermogravimetric analysis (TGA) provided insights into the thermal stability and AcOH desorption behaviour of FeBTC, supporting the evidence of AcOH interaction with the MOF. Scanning electron microscopy (SEM) revealed rapid transformation from irregular, blocky particles to hollow, cylinder‐like architectures within 14 h upon interaction with AcOH vapours. This morphological change was confirmed by USAXS/SAXS data, which also showed a steep relative increase in surface/volume (S/V) ratio at early exposure followed by a decrease at later stages compared to the initial value. This facile vapour phase modulator approach unlocks new possibilities for post‐synthetic control of MOF morphology and available interaction surface, with implications for gas capture, catalysis, and separation.