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

Abstract

<div><b>ABSTRACT</b> <br></div><div><br></div><div> Competition between atmospheric moisture and volatile organic compounds (VOCs) for an adsorbent’s sites can significantly impact its VOC removal efficiency. The development of moisture-tolerant adsorbents is essential to address this issue. A vapor phase deposition process using polydimethylsiloxane (PDMS) has created a hydrophobic form of the highly porous, normally hydrophilic, MOF MIL-101. After optimizing the PDMS vapor deposition time and molecular weights, hydrophobicity index calculations verified the improved hydrophobicity of the coated MOF (MIL-PDMS-Sigma-0.25) over its pristine form. The surface area, pore volume as well as single component vapor adsorption of water and toluene capacities were also preserved, resulting to similar performance to MIL-101. Toluene-water vapor co-adsorption experiments were conducted at 40% RH using two toluene concentrations: 0.5% P/P<sub>0</sub> and 10% P/P<sub>0</sub>, mimicking environmental VOC and industrial concentrations, respectively. At 0.5% P/P<sub>0</sub>, MIL-PDMS-Sigma-0.25 exhibited 60% higher adsorption capacity and twice the rate of toluene capture relative to pristine MIL-101, as well as a 3-fold higher toluene uptake relative to a commercial activated carbon. Preliminary adsorbent regeneration experiments confirm the stability and performance of MIL-PDMS-Sigma-0.25. Using a simple vapor phase modification, this new MOF-composite material offers superior competitive toluene vapor uptake in humidified real-world conditions at VOC concentrations. </div>