Net, Excess, and Absolute Adsorption of N2, CH4, and CO2 on Metal- Organic Frameworks of ZIF-8, MIL-101(Cr), and UiO-66 at 282-361 K and up to 12 MPa

Experimental gas adsorption data on particular porous solids, reported in the literature, typically disagree within large scales. Besides, the literature data are generally hard to be reproduced within stated uncertainties, and sometimes no uncertainty information is provided. Therefore, in an effort toward standardization of adsorption measurements, this work offers high-quality N-2, CH4, and CO2 adsorption data on three metal-organic frameworks (MOFs) of ZIF-8, MIL-101 (Cr), and UiO-66 with detailed traceable uncertainty information. The adsorption capacity of gases was measured with a gravimetric sorption analyzer, incorporated with a magnetic-suspension balance, over the temperature range of 282-361 K and pressure up to 12 MPa. The high-pressure adsorption data enabled us to study the micro- and mesoporosities of the adsorbents in more detail. The relative combined expanded uncertainty (k = 2) of the measured absolute adsorption capacity is in the order of 40 and 2% at the lowest and highest pressures, respectively. The measurement results show that MIL-101(Cr) has the highest adsorption capacity for all the three gases, followed by UiO-66 and ZIF-8; and all three MOFs, particularly UiO-66, present a reasonable selectivity for CO2 over CH4 and N-2 and have the potential to be utilized in the separation of CO2 from these gas mixtures.