UIO-67-TYPE METAL-ORGANIC FRAMEWORKS WITH ENHANCED WATER STABILITY AND METHANE ADSORPTION CAPACITY

The structure and properties of two new UiO-67-type metal–organic frameworks, along with their linker synthesis and powder and single crystal synthesis, are presented. The new MOFs, UiO-67-Me and UiO-67-BN, are based on 3,3-dimethylbiphenyl and 1,1-binaphthyl linker scaffolds, and show a much higher stability to water than the thoroughly investigated UiO-67, which is based on the biphenyl scaffold. On the basis of structure models obtained from single crystal X-ray diffraction, it is seen that these linkers are partly shielding the Zr cluster. The new materials have higher density than UiO-67, but show a higher volumetric adsorption capacity for methane. UiO-67-BN exhibits excellent reversible water sorption properties, and enhanced stability to aqueous solutions over a wide pH range; it is to the best of our knowledge the most stable Zr-MOF that is isostructural to UiO-67 in aqueous solutions. Access the research article here.

TUNED TO PERFECTION: IRONING OUT THE DEFECTS IN METAL-ORGANIC FRAMEWORKS UiO-66

This systematic study has demonstrated the dramatic yet logical impact that the synthesis conditions can have on the properties of UiO-66. Seven potential pitfalls regarding sample ideality were investigated, affording the conclusion that the material systematically becomes more “ideal” when the BDC:Zr ratio and/or synthesis temperature are increased. Such gravitation toward ideality makes sense when one notes that linker deficiencies are the underlying cause of the majority of pitfalls. We suggest that increasing the synthesis temperature and/or BDC:Zr ratio shifts the solution equilibrium in favor of BDC-Zr bonds, aiding the “ironing out” of linker deficiencies. This approach ultimately yields “ideal” UiO-66 with unsurpassed thermal stability when the synthesis is performed with a 2:1 BDC:Zr ratio at 220 °C. Access the research article here.

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