Efficient solvothermal synthesis of highly porous UiO-66 nanocrystals in dimethylformamide-free media

Abstract

The UiO-66 metal-organic framework has remarkable physicochemical characteristics which have positioned it as one of the Zr-MOFs with greater potential for application in diverse processes. However, it remains a challenge how to optimize the synthesis methods so as to obtain this material with high yield and good porous properties under more ecocompatible conditions. In this work, we report the solvothermal synthesis of UiO-66 nanocrystals with high surface area using acetone as the synthesis medium, replacing the traditional and toxic N,N-dimethylformamide. The effects of solvents, reactant concentration,temperature, synthesis time and mixture protocol on the material properties were characterized by XRD, SEM-EDS, FTIR, TGA-SDTA and N2 adsorption isotherms. The alternative protocol allowed obtaining UiO-66 with high yields (~91 %) without employing DMF, under mild conditions (80 ºC), in the form of nanocrystals with high specific surface area (1299 m2.g-1) that can be activated by simple drying at 130 ºC and atmospheric pressure. The MOF obtained in acetone under optimum conditions showed reversible CO2 uptakecapacity at room temperature and low pressures as determined by both CO2 isotherms and TGA-CO2 tests.