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.

A NEW ZIRCONIUM INORGANIC BUILDING BRICK FORMING METAL-ORGANIC FRAMEWORKS WITH EXCEPTIONAL STABILITY

Porous crystals are strategic materials with industrial applications within petrochemistry, catalysis, gas storage, and selective separation. Their unique properties are based on the molecular-scale porous character. However, a principal limitation of zeolites and similar oxide-based materials is the relatively small size of the pores, typically in the range of medium-sized molecules, limiting their use in pharmaceutical and fine chemical applications. Metal organic frameworks (MOFs) provided a breakthrough in this respect. New MOFs appear at a high and an increasing pace, but the appearances of new, stable inorganic building bricks are rare. Here we present a new zirconium-based inorganic building brick that allows the synthesis of very high surface area MOFs with unprecedented stability. The high stability is based on the combination of strong Zr−O bonds and the ability of the inner Zr6-cluster to rearrange reversibly upon removal or addition of μ3-OH groups, without any changes in the connecting carboxylates. The weak thermal, chemical, and mechanical stability of most MOFs is probably the most important property that limits their use in large scale industrial applications. The Zr−MOFs presented in this work have the toughness needed for industrial applications; decomposition temperature above 500 °C and resistance to most chemicals, and they remain crystalline even after exposure to 10 tons/cm2 of external pressure. Access the Research article here.

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