I am pleased to be involved in this nice publication from my friend Florence Ragon ! This article about intra framework cross linking of anhydrides in UiO-66 MOFs has been accepted for publication in J. Mater. Chem. A.
The functionalization of metal-organic frameworks (MOFs) with free carboxylic groups is naturally difficult due to their potential coordination with metal ions. The impact of functionalizing the archetypical metal organic framework UiO-66(Zr) with free pending carboxylic groups was thus studied by a multi-technique approach.
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First, an environmentally-friendly water synthesis route was developed to produce UiO-66(Zr)-(COOH)x (x = 1, 2) and their kinetics of crystallization was followed by in situ energy dispersive X-ray diffraction. In a second step, their structural features were studied by temperature-dependent X-ray diffractometry and further characterized by density functional theory calculations and solid-state nuclear magnetic resonance spectroscopy. Their gas sorption properties, acidity and conductivity features were respectively assessed by gas isotherms and calorimetry, infrared spectroscopy and complex impedance spectroscopy. These data show the noticeable influence of the acidic groups introduced. Finally, it was shown that the thermal treatment of such solids leads to an intra-framework cross-linking associated with the formation of anhydride bridges, as evidenced by FTIR and solid-state NMR, and modelled by DFT simulations. These species have a strong impact on the acidity, but a limited effect on gas sorption properties at room temperature. The reversibility of the carboxylic acids to anhydrides transformation was also assessed.