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

• Published in: Crystal growth & design Vol. 13; no. 11; pp. 5036 - 5044
• Main Authors: Carson, Fabian, Su, Jie, Platero-Prats, Ana E, Wan, Wei, Yun, Yifeng, Samain, Louise, Zou, Xiaodong
• Format: Journal Article
• Language: English
• Published: Washington,DC American Chemical Society 06.11.2013
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Inorganic Chemistry; Materials science; oorganisk kemi; Organic compounds; Other materials; Physics; Porous materials; granular materials; Specific materials; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Metal organic framework; pH value; Porous materials; Organometallic compounds; XRD; X-ray absorption; Metal clusters; Isomers; Isomerism; Mesoporosity; Transition elements; Surface area; Polymorphism; Crystal structure
• ISSN: 1528-7483; 1528-7505; 1528-7505
• DOI: 10.1021/cg4012058

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.