Ce(III) doped Zr-based MOFs as excellent NO2 adsorbents at ambient conditions

New hybrid cerium modified zirconium based metal-organic frameworks (MOFs) were synthesized. The as-received materials were evaluated as adsorbents of NO2 in either moist or dry conditions. The surface of the initial and exhausted samples was characterized using XRD, SEM-EDX, nitrogen adsorption, thermal analysis, and FTIR. It was found that the addition of Ce(+3) slightly affects the growth of the framework and introduces new features to Zr-MOF. The shapes of the octahedral crystals are changed, and they are interwoven with rod-flake-like sheets. The extent of the interconnection, and thus the extent of the hybrid MOF formation, depends on the Zr to Ce ratio. The alterations in the surface chemistry and texture are reflected in the amount of NO2 adsorbed. The narrow pore channels present in these new materials enhance adsorption in either moist or dry conditions. The amount of NO2 adsorbed on the Ce-doped MOF increases over 25% in dry conditions in comparison with the unmodified MOF. Exposure of Ce-UiO-66 to NO2 results in a development of porosity. Regardless the conditions, the XRD patterns indicate the stability of this new hybrid MOF upon NO2 adsorption. Interactions of NO2 with MOF result in the formation of nitrate and nitrite species associated either with metals or with organic ligands.