In Operando Spectroscopic Ellipsometry Investigation of MOF Thin Films for the Selective Capture of Acetic Acid

Sanchari Dasgupta; Subharanjan Biswas; Kevin Dedecker; Eddy Dumas; Nicolas Menguy; Bruno Berini; Bertrand Lavedrine; Christian Serre; Cédric Boissière; Nathalie Steunou

doi:10.1021/acsami.2c17682

In Operando Spectroscopic Ellipsometry Investigation of MOF Thin Films for the Selective Capture of Acetic Acid

ACS Appl Mater Interfaces. 2023 Feb 1;15(4):6069-6078. doi: 10.1021/acsami.2c17682. Epub 2023 Jan 18.

Affiliations

¹ Institut Lavoisier de Versailles, UMR CNRS 8180, Université de Versailles St Quentin en Yvelines, Université Paris Saclay, 78035 Versailles, France.
² UMR CNRS 7590, MNHN, IRD, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), Sorbonne Université, 75005 Paris, France.
³ Groupe d'Etudes de la Matière Condensée, UMR CNRS 8635, Université de Versailles St Quentin en Yvelines, Université Paris Saclay78035 Versailles, France.
⁴ Centre de Recherche sur la Conservation, UAR CNRS 3224, Muséum National d'Histoire Naturelle, 75005 Paris, France.
⁵ Institut des Matériaux Poreux de Paris (IMAP), Ecole Normale Supérieure de Paris, ESPCI Paris, CNRS, PSL University, 75005 Paris, France.
⁶ CNRS, Collège de France, UMR Chimie de la Matière Condensée de Paris, Sorbonne Université, 75005 Paris, France.

PMID: 36654492
DOI: 10.1021/acsami.2c17682

Abstract

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, etc.) 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 ellipsometry in operando study (2-6% of relative pressure of AA under 40% of RH), namely conditions close to the realistic environmental storage conditions of cultural artifacts. 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 coadsorbed analytes (water and AA) was identified by FT-IR ellipsometry. While thin films of ZIF-8(Zn) strongly degraded upon exposure to AA/water vapors, 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 selectivity under humid conditions. In contrast, UiO-66(Zr)-2CF₃ was shown to overpass MIL-101(Cr) in terms of AA/H₂O adsorption selectivity and AA adsorption/desorption cycling stability because of its high hydrophobic character, suitable pore size for adequate confinement, and specific interactions.

Keywords: MOFs; adsorption; ellipsometry; thin films; volatile organic compounds.