Direct Air Capture of Carbon Dioxide into MFI Frameworks by Low-Temperature Swing Under Realistic Humidity

The urgent need to combat global warming inspired the introduction of the concept of carbon dioxide direct air capture (CO₂-DAC), a key strategy for decentralized greenhouse gas removal from air. In this study, a simple approach for CO₂-DAC is introduced, utilizing ZSM-5 and its ion-exchanged analogues to effectively concentrate CO₂ from humid air (80% RH) at 5 °C and enable its recovery at a moderate desorption temperature of 25 °C where in both cases, ambient air served as a sustainable CO₂ source and desorption medium. Repeated adsorption (5 °C) and desorption (25 °C) cycles confirm the adsorbent stability under realistic conditions. Based on Monte Carlo (MC) and molecular dynamics (MD) simulations, a preferential CO₂ adsorption via electrostatic interactions with minimal competitive adsorption with H₂O is observed, explained by the facile diffusion of CO₂ into the micropores compared to the preferred H₂O adsorption on the outer surface of the zeolite. These experimental and theoretical insights pave the way for industrial CO₂-DAC applications using zeolite-based adsorbents.