Hydrophobic MOFs for the efficient capture of highly polar volatile organic compound

Abstract

Effective capture of polar volatile organic compounds under environmental conditions is a challenge owing to the adsorption competition between polar volatile organic compounds and water. The best adsorbents usually exhibit a compromise between a moderate affinity towards the VOC and hydrophobicity. Herein, by conducting experimental (sorption isotherms, dynamic measurements, X-ray diffraction, and solid-state NMR) and computational (Monte Carlo and density functional theory) studies, we demonstrate that introducing perfluorinated groups within the flexible microporous MOF increases hydrophobicity and its MIL-53(Al) MOF increases hydrophobilicty and leads to higher affinity to VOCs. Remarkably, MIL-53(Al)-CF₃ exhibits an outstanding affinity for acetic acid even in the presence of water, while its MIL-53(Al)-2CF₃ analogue, owing to steric hindrance, is not efficient. Therefore, perfluorinated flexible MIL-53(Al) with one CF₃ group appears as an optimum sorbent for indoor air quality management under real working conditions, especially for high-end applications that require the removal of trace levels of VOCs under environmental conditions.