The emission of polar volatile organic compounds (VOCs) is a major worldwide concern of air quality and equally impacts the preservation of cultural heritage (CH). The challenge is to design highly efficient adsorbents able to selectively capture traces of VOCs such as acetic acid (AA) in the presence of relative humidity (RH) normally found at storage in museums (40-80%). Although the selective capture of VOCs over water is still challenging, Metal-Organic Frameworks (MOFs) possess highly tunable features (Lewis, Bronsted or redox metal sites, functional groups, hydrophobicity…) suitable to selectively capture a large variety of VOCs. In this context, we have explored the adsorption efficiency of a series of MOFs thin films (ZIF-8(Zn), MIL-101(Cr) and UiO-66(Zr)-2CF3) for the selective capture of AA based on a UV/Vis and FT-IR spectroscopic ellip-sometry in operando study (2-6% of relative pressure of AA under 40% of RH), namely conditions close to the realistic envi-ronmental storage conditions of cultural artefacts. For that purpose, optical quality thin films of MOFs were prepared by dip-coating and their AA adsorption capacity and selectivity were evaluated under humid conditions by measuring the variation of the refractive index as a function of the vapor pressures while the chemical nature of the co-adsorbed analytes (water and AA) was identified by FT-IR ellipsometry. While thin films of ZIF-8(Zn) strongly degraded when exposed to AA/water va-pors, films of MIL-101(Cr) and UiO-66(Zr)-2CF3 present a high chemical stability under those conditions. It was shown that MIL-101(Cr) presents a high AA adsorption capacity due to its high pore volume, but exhibits a poor AA adsorption selectivi-ty under humid conditions. In contrast, UiO-66(Zr)-2CF3 was shown to overpass MIL-101(Cr) in terms of AA/ H2O adsorp-tion selectivity and AA adsorption/desorption cycling stability thanks to its high hydrophobic character, suitable pore size for adequate confinement and specific interactions.