Zr-based metal-organic framework with dual BrØnsted acid-base functions

Design and synthesis of metal-organic frameworks (MOFs) with multi-functionality have attracted a lot of attention since the different functional groups can enhance the cooperative effect providing properties superior to those found in mono-functional MOFs. The efficiency and selectivity of the reactions can be improved by the simultaneous activation of multi-functional catalysts. Herein, a series of BrØnsted acid-base bifunctional UiO-66 bearing acidic sulfo- and basic amino- functional groups were successfully prepared via a simple one-pot solvothermal method. PXRD patterns of the bifunctional frameworks were similar to that of simulated UiO-66. The existence of sulfo-and amino- functional groups was investigated by IR and H¹-NMR. The bifunctional frameworks showed high thermal stability up to 300°C examined by TGA. By varying the molar ratios of ligands, the proportions of acidic and basic moieties in the framework were successfully tuned. The amount of functional groups anchoring in resulting frameworks was determined by ¹H-NMR. This bifunctional UiO-66 was tested for CO₂ capture. (paper)