Impact of scale, activation solvents, and aged conditions on gas adsorption properties of UiO-66.

This work reports on the potential application of UiO-66 in gas sweetening and its structural stability against water, air, dimethylformamide (DMF), and chloroform. The UiO-66 nanoparticles were solvothermally synthesized at different scales and activated via solvent exchange technique using chloroform, methanol, and ethanol. Thus prepared and aged MOFs were characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), and nitrogen adsorption-desorption analysis. The chloroform-activated MOF showed the largest surface area among all activation solvents, and presented high uptakes of 8.8 and 4.3 mmol/g for CO2 and CH4, respectively, at 298 K and 30 bar. This might be due to removing all unreacted organic ligands and DMF molecules from the pores of the framework. The UiO-66 nanoparticles are stable at the experimental conditions with no significant loss in crystalline structure and gas adsorption ability even after aging under different conditions for one year. The UiO-66 could be easily regenerated at 373 K with no observed significant reduction in gas uptakes even after five consecutive adsorption-desorption cycles. The present findings suggest the excellent potential of the UiO-66-derived MOFs as the promising materials for CO2/CH4 separation at low pressures and results can be applied in practical natural gas sweetening.