Engineering adsorption selectivity in MFI zeolites through suppression of silanol-driven water competition for efficient acetone capture.

Efficient physisorption of acetone for indoor air purification critically depends on selecting a hydrophobic sorbent with relatively small pores, which not only provides optimal confinement for acetone molecules but also minimizes competitive adsorption of water. Here, we first systematically assessed, by density functional theory calculations, the adsorption behaviors of both acetone and water in pure silica and a series of metal-modified MFI type zeolites. These simulations reveal that in the pure silica MFI, acetone and water compete for adsorption at the silanol groups, and the incorporation of molybdenum effectively reduces the presence of these hydrophilic silanol groups. Consequently, metal incorporation reduces the H2O affinity of the zeolite framework favoring a selective adsorption of acetone over water via a coordination of its carbonyl oxygen atoms to the metal sites. In situ FTIR measurements confirmed that Mo-containing MFI largely devoid of surface silanols promotes interactions with the Mo species and extra-physisorption within the zeolite channels. Dynamic breakthrough experiments demonstrated enhanced acetone capture by Mo-MFI compared with Si-MFI in the presence of water. This joint experimental-computational study demonstrates that Mo-containing, silanol-annealed MFI zeolite is a highly efficient microporous adsorbent for the challenging selective adsorption of acetone under real conditions, i.e. in the presence of water.