A Breathing Hybrid Organic-Inorganic Solid with Very Large Pores and High Magnetic Characteristics

Abstract

Porous solids [1] usually find applications in the areas of ionexchange, separation, and catalysis. The recent discovery of new materials based upon transition metal ions [2] opens the possibility of making open frameworks that exhibit also some of the remarkable electronic properties of condensed transition metal compounds (ferro-and ferrimagnetism, metalsemiconductor transitions, ferroelectricity, combined ionic/ electrical conductivity). Up to now, in the field of magnetism, the major limitation for producing porous solids with high ordering temperatures came from the structure itself. Indeed, most of the porous compounds are built from metallic clusters linked by diamagnetic linkers (phosphates, arsenates, silicates, aliphatic chains) which prevent strong, long-range interactions. To date, the highest Ne ¬ el temperatures were observed for the purely inorganic porous skeleton of ULM-3 [3] (37 K) and for the hybrid solid HKUST-1 [4] (75 K).To overcome this difficulty, our design strategy is to link chains of corner-sharing transition metal octahedra (which favor strong, long-range superexchange coupling) by rigid organic linkers containing delocalized p electrons for the three-dimensional transmission of the interactions. The use of such linkers was mainly developed by the groups of Yaghi and O×Keeffe, [5a] Zaworotko, [5b] and Kitagawa [5c] for metal-organic frameworks with modulable very large pores.As an example of our design principle, we describe here the synthesis, structure, magnetic and sorption properties of a large-pore, flexible, open framework (MIL-47) that is antiferromagnetic below 95 K.To implement this design, we used the hydrothermal reaction (teflon-lined steel autoclave Parr, four days, 473 K, autogenous pressure, filling rate: 50 %) of either a mixture of VCl 3 , terephthalic acid, and desionized water (molar ratio 1:0.25:100), which only provides homogeneous pure powders, or of vanadium metal, terephthalic acid, hydrofluorhydric acid, and water (molar ratio 1:0.25:2:250) when crystals are needed. In both cases, the pH value remains 1 throughout the synthesis and the yield is close to 15 %. The resulting light yellow product, (hereafter labeled MIL-47as), which is stable in air, is formulated V III (OH){O 2 C-C 6 H 4 -CO 2 } ¥ x(HO 2 C-C 6 H 4 -CO 2 H) (x $ 0.75) on the basis of elemental analysis (calcd: C 47.1, V 14.3; found: C 46.87, V 13.79;). Both thermodiffractometry and thermal analyses (TGA2050 TA apparatus, O 2 flow, heating rate 2 K min À1 ) show (Figure 1 a) a decomposition of MIL-47as in two steps between 300 and 420 8C. The first weight loss (exp.: 32.3 %, calcd: 34.92 % for proteins suggest that such a universal inhibitor design could potentially be effective against several different viruses. [18] [1] For a recent review, see A. G. Cochran, Chem.

Enhanced gas sorption and breathing properties of the new sulfone functionalized COMOC-2 metal organic framework

“…2. This latter band confirms the presence of hydroxyl groups and vanadium cations in the +III oxidation state in the SO 2 -COMOC-2 material, which was also proposed by Barthelet 38,39 XANES measurements were carried out to give additional proof for the presence of a mixed oxidation state within the SO 2 -COMOC-2 material. Nevertheless, it should be noted that all the reflections in the XRPD pattern of the SO 2 -COMOC-2 are slightly shifted to a higher 2θ angle in comparison to the pristine COMOC-2.…”

A Review on Breathing Behaviors of Metal-Organic-Frameworks (MOFs) for Gas Adsorption

“…However, the presence of μ 2 -oxo groups in MIL-47 framework yields the rigidity of its framework. Hence, MIL-47 only shows as a microporous material and exhibits no breathing behaviors [47,99]. How does the framework functionality affect their gas adsorption behaviors and breathing phenomena?…”

Unusually Large Band Gap Changes in Breathing Metal–Organic Framework Materials

“…MIL-47-V was previously considered as rigid, non-breathing 43 but recently, it was discovered that MIL-47-V can be transformed from the open lp form into the closed np form upon mechanical pressure, 44 hence we consider both np and lp forms of MIL-47 in our study as a comparator to MIL-53, the primary focus of this study. MIL-47-V has been well studied for several years, 45 whilst the experimental synthesis of MIL-53-Ti has not been reported so far, however, several other MOFs with titanium nodes exist, e.g. MIL-125 46-47 and NTU-9.…”