Experimental Study of CO2, CH4, and Water Vapor Adsorption on a Dimethyl-Functionalized UiO-66 Framework

A water resistant, highly robust dimethyl-functionalized UiO-66 analogue (UiO-66-DM) has been synthesized and characterized by using N 2 adsorption, powder X-ray diffraction, 1 H nuclear magnetic resonance, Fourier transform infrared spectroscopy, and thermogravimetric analysis followed by mass spectroscopy. High-pressure (up to 20 bar) single-component adsorption isotherm measurements of CO 2 and CH 4 have been performed on UiO-66-DM at different temperatures (293–308 K). Adsorption isotherm data were modeled by using the Toth equation, and isosteric heats of adsorption were calculated by using the Clausius–Clapeyron equation. The Ideal Adsorbed Solution Theory (IAST) was used to calculate mixture selectivities. Water adsorption experiments show that water adsorption loadings in UiO-66-DM are reduced by almost 50% compared to the parent material. In the low-pressure region, functionalization of the benzenedicarboxylic ligand by 2,5-dimethyl leads to higher interactions with both CO 2 and CH 4 compared to the parent UiO-66. CO 2 /CH 4 selectivity calculated from IAST is higher for UiO-66 in the low-pressure region (<5 bar) but for pressures >5 bar, UiO-66-DM is more CO 2 selective than UiO-66.