Innentitelbild: A Series of Isoreticular, Highly Stable, Porous Zirconium Oxide Based Metal–Organic Frameworks (Angew. Chem. 37/2012)

A Low‐Temperature Approach for the Phase‐Pure Synthesis of MIL‐140 Structured Metal–Organic Frameworks

“…The synthesis of MIL-140A (ZrO(bdc)), for example, is conducted at at emperature of 220 8Ca nd ar atio of ZrCl 4 /H 2 bdc/DMF of 1:2:80. [17] So, the synthesis mixture has ah igherc oncentration compared with the synthesis of UiO-type materials and an excesso fl inker is used to obtain the phase-pure product. According to the authors, the highs ynthesis temperature is necessary to obtain the MIL-140 material because lower temperatures lead to the related UiO-typematerial.…”

“…As already mentioned, the addition of am odulator is useful to synthesize UiO-67 or MIL-140C. [12,17,28] Upon the addition of acetic acid (10 to 30 equiv), crystalline products can be obtained (see Figure 6b-d). In general, there are three different areas discernible dependingo nt he concentration of precursors in the synthesis mixture.…”

“…According to the literature, no modulator is needed to obtain phase-pure MIL-140A. [17] By comparing the PXRD patterns of the corresponding products from syntheses conducted for 24 hw ithout the addition of modulators (see Figure 2a), it can be seen that UiO-66 is formed when an amounto f1 20 or 100 equivalents of DMF are used. With 80 equivalents of DMF and below,t he phase-pure synthesis of MIL-140A is possible.…”

“…By using the same linker molecules, Guillerm et al presented new Zr-based MOFs with even higher chemical and thermal stability. [17] In contrast to the UiO materials, the so-called MIL-140 series exhibits chains of sevenfold coordinated Zr cations as IBUs, which are oriented parallelt ot he c-axis of the structure. Each zirconiumo xide chain is connected to six other chains, resulting in at hree-dimensional framework.…”

“…In contrast to UiO materials, the members of the MIL-140 series are stable in boiling water. [17] This highert olerance towards water can be explained with the more hydrophobic charactero ft he MOFs. In case of the MIL-140B, an interesting potentiala pplication is the protection of cultural heritage through ah igh adsorption of acetic acid from air withoutdegradation.…”