Bifunctionalized metal organic frameworks, UiO-66-NO₂-N (N = -NH₂, -(OH)₂, -(COOH)₂), for enhanced adsorption and selectivity of CO₂ and N₂

Abstract

Metal organic frameworks (MOFs), UiO-66-NO2 and UiO-66-NO2–N (N = -NH2, -(OH)2, -COOH)2), were synthesized under solvothemal conditions using different functionalized organic linkers. The synthesized samples were further activated by solvent exchange using methanol and chloroform. All samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and N2 adsorption/desorption. Gas adsorption of CO2 and N2 on all samples has been evaluated at 760 mmHg and different temperatures. It was found that UiO-66-NO2-NH2 by methanol or chloroform activation presented much higher CO2 adsorption than other samples and the adsorption capacities are around (87 and 74) cm3·g–1 on chloroform-activated and methanol-activated samples, respectively, at 273 K and 760 mmHg. In addition, high selectivity of CO2/N2 has been found on chloroform-activated UiO-66-NO2-NH2 giving a factor of 65 while the selectivity of CO2/N2 is only 40 for chloroform-activated UiO-66-NO2.