The development of microporous pillared layered materials for volatile organic compound adsorption and N-2/O-2 separation

Al-pillared montmorillonite has been prepared by intercalation of [Al13O4 ( OH)(24) (H2O)(12)](7+) or Keggin ions in the interlayer space of the clay. After calcination, the Al-13 ions were converted into the Al2O3 form, resul ting in a stable structure with a large Langmuir surface area of 403 m(2)/g and a micropore volume of 0.130 cc/g. Subsequently, the Al-PILC was modifi ed with different cations (Ca2+, Sr2+) and anions (Cl-, PO43-, F-) based on ion exchange at the hydroxyl groups present on the pillared clay, in basic and acid environments, respectively. The introduced ions functioned as spe cific adsorption sites and influenced the affinity of the PILC for certain gases, e.g. N-2, O-2 and CO2. High N-2/O-2 ratios were obtained for the cat ion modified Al-PILC at 273K, while in the case of an anion exchanged subst rate O-2 was selectively more adsorbed than N-2. The results are explained in terms of the interactions between the PILC and specific physicochemical properties of the gases. A second synthesis approach, which is based on a s elf-assembly method, allowed the deposition of Al-pillared laponite films o n a Au-support. Characterization of the growing films was performed using e llipsometric thickness measurements which indicated a homogeneous and regul ar layer-by-layer growth. The films were used as chemically sensitive mass sensors on surface acoustic wave (SAW) devices to measure the adsorption ca pacity of six volatile organic compounds. The influence of the different te rminal film layers, the film thickness and calcination-induced chemical cha nges on the adsorbed VOC mass was apparent.