Fe-MOF

Fig. 8 Electron microscopy images of (a, b) hollow Fe -MOF-5 template and (c, d) porous hybrid Zn0/ZnFe204/C nanocomposite after annealing, showing nanoparticles with an average diameter of 5 nm. Modified with permission from ref. 39. Copyright 2014 Wiley-VCH. ...

This selectivity results from the UMCs (iron or copper) located in the active sites of metalloproteins. Similarly, the UMCs, especially unsaturated iron centers, will significantly facilitate this process in MOFs as well. The M-MOF-74 series are renowned for their high density of UMCs, and Fe-MOF-74 was reported as an efficient adsorbent for O2 storage and O2/N2 separation owing to the existence of unsaturated Fe(II) centers. This MOF was synthesized by air-free procedures, and it has a BET surface area of 1360m -g . After a full activation, Fe-MOF-74 [also known as Fe2(dobdc)] preferentially binds O2 over N2 at all temperatures. 

Figure 18 (a) The representation of crystal structure of Fe-MOF-74 with Oj at 100 K. Oj was bond in a side-on manner at this temperature, (b) The crystal structure of Fe-MOF-74 with Oj at 298 K. At this temperature, the ferrous centers were oxidized to the ferric ions, and they were bonded to a peroxide anion, (c) Excess Oj adsorption isotherms collected for Fe-MOF-74 at 211 K (orange), 226 K (purple), and 298 K (red) and Nj adsorption at 298 K (blue), (d) Tlie coordination sphere of iron centers with Oj at 100 K. (e) The coordination sphere of iron centers with Oj at 298 K. (c-e Reprinted with permission from Ref 36. Copyright (2011) American Chemical Society.)... 

Softening point (°C) Class transition temp., Tg fC) fe mof ) Acid number (tt KOHg- )... 

Another SBU with open metal sites is the tri-p-oxo carboxylate cluster (see Section 4.2.2 and Figure 4.2). The tri-p-oxo Fe " clusters in MIL-100 are able to catalyze Friedel-Crafts benzylation reactions [44]. The tri-p-oxo Cr " clusters of MIL-101 are active for the cyanosilylation of benzaldehyde. This reaction is a popular test reaction in the MOF Hterature as a probe for catalytic activity an example has already been given above for [Cu3(BTC)2] [15]. In fact, the very first demonstration of the catalytic potential of MOFs had aheady been given in 1994 for a two-dimensional Cd bipyridine lattice that catalyzes the cyanosilylation of aldehydes [56]. A continuation of this work in 2004 for reactions with imines showed that the hydrophobic surroundings of the framework enhance the reaction in comparison with homogeneous Cd(pyridine) complexes [57]. The activity of MIL-lOl(Cr) is much higher than that of the Cd lattices, but in subsequent reaction rans the activity decreases [58]. A MOF with two different types of open Mn sites with pores of 7 and 10 A catalyzes the cyanosilylation of aromatic aldehydes and ketones with a remarkable reactant shape selectivity. This MOF also catalyzes the more demanding Mukaiyama-aldol reaction [59]. 

Fig. 6.15 (a) Synthetic routes to make graphene-porphyrin MOF (a) G-dye synthesized from rGO sheets via diazotization with 4-(4-aminostyryl) pyridine, (b) (Fe-P)n MOF synthesized via reaction between TCPPs and Fe ions, (c) (G-dye-FeP)n MOF formed via reaction between (Fe-P)n MOF and G-dye (from [161]). 

The activation volume for peroxodisulfate oxidation of [Fe(CN)5(pentylpz)] , 0 2cm moF suggests, as do the close-to-zero values for analogous reactions of [Fe(CN)6j" and of [Fe(diimine)(CN)4], compensation between intrinsic and solvational contributions." ... 

A values have been obtained for oxidation of benzenediols by [Fe(bipy)(CN)4], including the effect of pH, i.e., of protonation of the iron(III) complex, and the kinetics of [Fe(phen)(CN)4] oxidation of catechol and of 4-butylcatechol reported. Redox potentials of [Fe(bipy)2(CFQ7] and of [Fe(bipy)(CN)4] are available. The self-exchange rate constant for [Fe(phen)2(CN)2] has been estimated from kinetic data for electron transfer reactions involving, inter alios, catechol and hydroquinone as 2.8 2.5 x 10 dm moF s (in dimethyl sulfoxide). 

Extensive replacement of Fe by transition metal cations and alkaline earth ions has been reported for b-FeOOH (Okamoto, 1968). Muller et al. (1979) found incorporation of up to 0.4 mol moF Ca solid solutions with the formula Fei xKxOi x(OH)i+x could be identified. Jimenez-Mateos et al. (1990) reported that Co and Mn, respectively, could replace up to 0.3 and 0.5 mol mol Fe. The unit cell parameters decreased in both cases with increasing substitution. These Mn- and Co-substituted 5-FeOOHs decomposed at 200 °C to give poorly crystalline, substituted hematites. 

Since the initial report of CuBF4[Cu(TPyP)] , several other TPyP MOFs have appeared wherein the pyridyl moieties are coordinated to nodes that consist of simple metal ions. The metal ion nodes have included Fe (119), Ag (120), Cd " (121), Pb (121), and Ru (122). In many cases, the secondary metal nodes bear additional hgands, for example as coordinated solvent molecules or counterions. Thus, the coordination geometries about the metal nodes and the resulting topologies are partly determined by the availability of pyridyl coordination sites and the geometric preferences of the metal nodes. 

The shoulder observed in Fig. 5(a) at 2078 cm is assigned to the free CN ejected. The CN anion is only seen as a shoulder, as its extinction coefficient is much weaker than when it is bound within a complex. We determined an integrated absorption coefficient of 840 moF dm cm" for the CN band at 2080 cm" and an integrated absorption coefficient for Fe(CN)g of 97,000 mol dm cm . The integrated absorption coefficient for Fe(CN) was determined as 15,800 moF dm cm . These determinations of integrated absorption coefficients enable us, after deconvolution of the peaks observed thanks to a fitting procedure, to know exactly the concentrations of the different species detected. 

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