Polydimethyl siloxane/MIL-101 Composites for Enhanced Toluene Adsorption in the Presence of Humidity

Abstract

ABSTRACT \nCompetition\nbetween atmospheric moisture and volatile organic compounds (VOCs) for an\nadsorbent’s sites can significantly impact its VOC removal efficiency. The\ndevelopment of moisture-tolerant adsorbents is essential to address this issue.\nA vapor phase deposition process using polydimethylsiloxane (PDMS) has created\na hydrophobic form of the highly porous, normally hydrophilic, MOF MIL-101.\nAfter optimizing the PDMS vapor deposition time and molecular weights,\nhydrophobicity index calculations verified the improved hydrophobicity of the\ncoated MOF (MIL-PDMS-Sigma-0.25) over its pristine form. The surface area, pore\nvolume as well as single component vapor adsorption of water and toluene\ncapacities were also preserved, resulting to similar performance to MIL-101.\nToluene-water vapor co-adsorption experiments were conducted at 40% RH using\ntwo toluene concentrations: 0.5% P/P0 and 10% P/P0,\nmimicking environmental VOC and industrial concentrations, respectively. At\n0.5% P/P0, MIL-PDMS-Sigma-0.25 exhibited 60% higher adsorption\ncapacity and twice the rate of toluene capture relative to pristine MIL-101, as\nwell as a 3-fold higher toluene uptake relative to a commercial activated\ncarbon. Preliminary adsorbent regeneration experiments confirm the stability\nand performance of MIL-PDMS-Sigma-0.25. Using a simple vapor phase\nmodification, this new MOF-composite material offers superior competitive\ntoluene vapor uptake in humidified real-world conditions at VOC concentrations.