Framework Isomerism in Vanadium Metal–Organic Frameworks: MIL-88B(V) and MIL-101(V)

Abstract

Two families of metal−organic frameworks (MOFs), MIL-88 and MIL-101 built by trinuclear transition metal (TM) clusters (TM = Cr, Fe, or Sc), have been known for several years, but their syntheses are often reported separately. In fact, these MOFs are polymorphs, or framework isomers: they are assembled from the same metal secondary building units and organic linkers, but the connectivity of these components differs. Here we report for the first time the synthesis of the vanadium MOF MIL-88B(V) and compare its synthesis parameters to those of MIL-47(V) and the recently reported MIL-101(V). The properties of MIL-88B(V) and MIL-101(V) are remarkably different. MIL-88B(V) can "breathe" and is responsive to different solvents, while MIL-101(V) is rigid and contains mesoporous cages. MIL-101(V) exhibits the highest specific surface area among vanadium MOFs discovered so far. In addition, both MIL-88B(V) and MIL-101(V) transform to MIL-47 at higher temperatures. We have also identified the key synthesis parameters that control the formation of MIL-88B(V), MIL-101(V), and MIL-47: temperature, time, and pH. This relates to the rate of reaction between the metal and linkers, which has been monitored by ex situ X-ray powder diffraction and V K-edge X-ray absorption spectroscopy during MOF synthesis. It is therefore important to fully study the synthesis conditions to improve our understanding of framework isomerism in MOFs.

Replacement of Chromium by Non-Toxic Metals in Lewis-Acid MOFs: Assessment of Stability as Glucose Conversion Catalysts

“…There is also evidence in the PXRD for the presence of an impurity phase in the sample, which we identify below as being MIL-88B ( Figure 1) [47]. It is already known that MIL-88B and MIL-101 are "framework isomers" and may form in competition to each other [4,48,49]. 3 also shows PXRD patterns of materials prepared where small amounts of Sc 3+ are used to replace some of the Fe 3+ , or some of the BDC linker is replaced by mono-2-sulfobenzene-1,4-dicarboxylate (MSBDC).…”

“…Biomass-derived glucose has received considerable attention as a potential feedstock for the production of useful organic molecules. One attractive target of glucose conversion is the molecule 5-hydroxymethyl furfural (5-HMF): this is regarded as a platform molecule that can be used as a precursor for an extensive range of plastics, polymers, and fuels [1][2][3][4]. Acid catalysts are needed to bring about the transformation of glucose, via fructose, into 5-HMF, and both Lewis and Brønsted acids have been implicated in the transformation mechanism [5][6][7][8].…”

Nanoscale Metal–Organic Frameworks Decorated with Graphene Oxide for Magnetic Resonance Imaging Guided Photothermal Therapy

“…These two frameworks, Fe-MIL-88B-NH 2 (B refers to the use of BDC as the linker) andF e-MIL-101-NH 2 ,a re topological framework isomers; they are assembled from the same components, but their connectivity is different, as shown in Figure 1a. [51,52] Powder XRD was used to investigate the crystalline framework and TEM was applied to investigate the morphology.F igure 1b shows the powder XRD patterns for as-synthesized Fe-MIL-88B-NH 2 and Fe-MIL-101-NH 2 (red lines in Figure 1b). As a reference, the corresponding simulated power XRD patterns createdf rom the crystallographic information file (CIF) are also presenti nF igure 1b (black lines).…”

Time‐Resolved In Situ X‐ray Diffraction Reveals Metal‐Dependent Metal–Organic Framework Formation

“…In the Al/NH 2 ‐bdc system (NH 2 ‐bdc=2‐amino‐1,4‐benzenedicarboxyalte), multiple routes to MIL‐53(Al) were observed in situ, including a MOF‐235 to MIL‐101 different to MIL‐53 pathway . The sequential formation of several MOF phases from the same reaction mixture has also been observed in situ for the Fe/bdc (bdc=1,4‐benzenedicarboxylate) and Li/tartrate systems, and ex situ for the V/bdc system …”