Active Adsorbents for Molecular Separation

Molecular separation plays a key role in energy and environmental technologies. Here we present our recent discovery of a new “active” molecular sieving mechanism – “molecular trapdoor” – in a class of chabazite zeolites through combined experimental and atomistic simulation works. These trapdoor chabazite absorbents have their eight-membered-ring (8MR) aperture (the only possible gas passage) blocked by some extraframework cations. Some specific gas molecules can interact with the aperture-keeping cations to induce temporary and reversible cation deviation from the center of 8MR aperture, allowing for the gas admission. The different chemical/physical interaction capability of various gas molecules with the aperture-keeping cations endows a selective gas admission, which is in striking contrast to conventional sieving mechanism where the molecular size plays a decisive role. A novel absorption model is developed to quantitatively describe the isobar adsorption curves (i.e., adsorption amount as a function of temperature) for our “active” trapdoor chabazites.