UiO-66 is one of the few known water-stable MOFs that are readily amenable to direct ligand substitution. In this work, UiO-66 has been synthesized with amino-, nitro-, methoxy-, and naphthyl-substituted ligands to impart polar, basic, and hydrophobic characteristics. Pure-component CO(2), CH(4), N(2), and water vapor adsorption isotherms were measured in the materials to study the effect of the functional group on the adsorption behavior. Heats of adsorption were calculated for each pure gas on each material. The results indicate that the amino-functionalized material possesses the best adsorption properties for each pure gas due to a combination of polarity and small functional group size. The naphthyl-functionalized material exhibits a good combination of inhibited water vapor adsorption and high selectivity for CO(2) over CH(4) and N(2).

Adsorption isotherms are reported for pure carbon dioxide on zeolite 13X (also called zeolite NaX) pellets over a temperature range of 0 to 200 °C and a pressure range of 0.001 to 100 kPa. These pure-component equilibria are fit with Langmuir, Toth, two-site Langmuir, and three-site Langmuir models, both with and without temperature dependence being included in the saturation capacity. The agreement between fitted and measured isotherms is shown to increase with increasing number of available fitting parameters in the model, with the constant-saturation, twosite Langmuir isotherm providing the best balance between agreement with the measurements and model complexity. The isosteric heats of adsorption are measured across a temperature range from 10 to 200 °C using differential scanning calorimetry. The measured heats of adsorption decrease with increasing CO 2 loading but show little variation with temperature. The measurements are shown to agree with predicted heats of adsorption derived from the fitted Langmuir and Toth isotherms (via the Clausius−Clapeyron equation); the heats of adsorption predicted using the more complex multisite Langmuir models suffer from nonphysical artifacts.

Adsorption isotherms are reported for pure water vapor on zeolite 13X (also called zeolite NaX) pellets. Data were obtained using a gravimetric method over a temperature range of 25 to 100 °C and a pressure range of 0.006 to 25 kPa. These pure-component equilibria are fit with the Sips, Toth, and multisite Langmuir models, all modified with the Aranovich–Donohue (A–D) model. The A–D Sips isotherm is recommended for modeling water adsorption on zeolite 13X because it provides the best agreement with the measured isotherm data.

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