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 eco-compatible 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,Ndimethylformamide. 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 N 2 adsorption isotherms. The sample obtained in pure acetone employing the optimized protocol exhibited spherical nanoparticles 150 nm in size and presented the greatest relative crystallinity. The alternative protocol allowed obtaining UiO-66 with high yields (* 91%) without employing DMF, under mild conditions (80 °C), in the form of nanocrystals with high specific surface area (1299 m 2 g -1 ) that can be activated by simple drying at 130 °C and atmospheric pressure. The MOF obtained in acetone under optimum conditions showed reversible CO 2 uptake capacity at room temperature and low pressures as determined by both CO 2 isotherms and TGA-CO 2 tests.

The application of Metal-Organic Frameworks (MOFs) in gas phase heterogeneous catalysis is still not widely spread because of their limited stability under reaction conditions. Obtaining stable acidic MOFs to be used in reactions that demand strong acid sites remains a challenge up to the present time. In this work, it is shown that nanocrystals of Zirconium MOF UiO-66 can be conveniently and easily functionalized through a simple one-pot synthetic approach, i.e. the direct treatment of UiO-66 with ammonium sulfate followed by an adequate thermal treatment, giving rise to a highly acidic and thermally stable material (named as S-UiO-66). This material can act as catalyst in the gas phase isobutene dimerization demonstrating high catalytic activity at moderate temperatures while maintaining the structural integrity of the MOF after several catalytic evaluations and/or after reuse cycles. The S-UiO-66 material represents a novel alternative in the search of robust MOF-based catalysts to be applied in gas phase heterogeneous catalytic reactions that demand strong acid sites.

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