Au@MOF

Doping of Metal-Organic Frameworks with Functional Guest Molecules 4.2.3 Cu MOF-5 and Au MOF-5... 

In contrast, TEM and PXRD data of Au MOE-5 show polydispersed Au particles in a size range of 5-20 nm (see Fig. 17), with a metal loading in Au MOF-5 determined to be 48 wt%. The gold particles appear to interact more weakly with the host matrix than the Pd, Ru and Cu particles and thus larger agglomerates are formed possibly by diffusion of the particles to the outer surface. 

Fig. 17 Powder X-ray diffraction patterns of (a) MOF-5, (b) Au MOF-5 and (c) TEM picture of Au MOF-5 [59]. Copyright Wiley-VCH Verlag GmbH Co. KGtiA. Reproduced with permission...

The compound Pd/MOF-5 exhibits a moderate catalytic activity in the hydrogenation of cyclooctene, and Cu/MOF-5 catalyzes the formation of methanol from the synthesis gas (220 °C, CO/H ). In contrast, highly porous Au/MOF-5 is inactive in the catalytic reduction of CO (because of the lability of the system). 

CUDOS-MOF http //www.physics.usyd.edu.au/cudos/mofsoflware/index.html... 

Separation of gold from copper, platinum, palladium, nickel, zinc, cadmium and mercury using triphenylarsine oxide as an extractant has been described [1]. The reaction of NN-dimethyl-p-phenylenediamine with Au in the presence of potassium persulfate made a basis of sensitive method for the determination of Au (e= 1.9 10 1 mof cm ) [2]. 

MOFs). Finally, the CCDC structure code for each material (where available) has been included in addition to the primary literamre reference. AU hgures were produced using CrystalMaker [V5.2, from the published crystallographic information hies (ClFs)] or ChemWindow (V3.1). 

Using the reaction rate observed (in moFs m ataiyst) in experiments performed at 150 rpm, the Wheeler-Weisz modulus was calculated for aU monoUths by estimating the layer thickness (L) from the carbon yield. inside the carbon layers was estimated to be 1 to 3 x 10 ° m /s inside the varions carbons. The valnes for are presented in Table 11.5. For 1-Al, consisting mainly of macroporons carbon, it is likely that internal diffusion limitations are present inside the carbon walls (where the lipase is located). This was also indicated by the decreased activity per gram of enzyme for these monoliths (Table 11.5). For ceramic monoliths, all adsorbed enzyme is used effectively (a constant tnmover freqnency for all carbon types), as confirmed by the low valnes for... 

In the first report on the synthesis of metal nanoparticles inside MOF-5, the formation of Pd, Cu and Au nanoparticles inside this framework was presented [59]. After loading with the corresponding precursors [CpPd(ri -C3H5)], [CpCu(PMe3)j or [Au(CH3)(PMe3)l, (see above) decomposition of the precursor to nanoparticles was achieved by either photolysis (UV radiation) or hydrogenolysis. Both, UV radiation and H3 treatment, even at elevated temperatures, left MOF-5 unchanged, with controlled decomposition of precursor molecules only. 

Fig. 15 XANES (left) and EXAFS (right) of (a) Ru MOF-5, (b) [Ru(cod)(cot) MOF-5, (c) Ru-ox MOF-5, (d) Ru foil and (e) RuOj. AU data were recorded at Uquid nitrogen temperature. Reproduced with permission [64], Copyright 2008 American Chemical Society...

Fig. 5. Arrhenius plots of the natural log of the equilibrium constant, Ka, versus lOOG/r for all experimental data Kq values from Table 5). The slope of the visually estimated curve is —E /R. AU laboratory run data are plotted for (a) controlled higher oxidation states, =22.1kJmol and (b) controlled lower oxidation states, E = 21.6 kJ moF ...

When the M (or Mi and M2) sites are located on a surface, the OH groups bound to them are commonly designated as surface OH groups. There is no consensus on the exact definition as to what constitutes a surface OH group. In many cases, for example, in zeolites and metal-organic frameworks (MOFs), the hydroxyls are intrinsic to the structure. However, they are referred to as surface hydroxyls because of their accessibility. Hereafter, we will denote as surface hydroxyls aU hydroxyls that are accessible to small molecules, because we believe this definition to be sensible in the context of catalysis. 

As mentioned earlier, the entropy of water under ambient conditions T= 298 K and atmospheric pressure) is equal to 16.8 cal-K -mor. Valuable insight can be obtained if we compare this amount with the entropy of water in the gas phase. Under ideal gas approximation, we obtain translational entropy from the well-known Sackur-Tetrode equation, Eq. (19.19), equal to 20.3 cal K mor (e.u.), we obtain rotational entropy equal to 10.5 cal K mor and vibrational entropy equal to 0.1 cal-K mor. These are in ambient conditions. Adding aU these, we obtain the value 30.9 cal-K moU which is larger than ftie experimental liquid state value by more than 14 cal K -moF ... 

Relativistic effects (see Box 13.2) have a profound influence on the ability of gold to exist in the —1 oxidation state. The enthalpy of attachment of the first electron to Au (equation 23.161) is -223kJmor, a value that lies between those for iodine (-295 kJ moF ) and sulfur (-201kJmoF ). 

To explore this question, the adsorption of glycine on AlOOH was recently investigated at the interface with water [78, 97]. This study confirmed the occurrence of an inner sphere Al-O-C-0 bond that was predicted from calculations at the interface with vacuum, and from numerous experimental studies of carboxylic acid adsorption on alumina polymorphs (see Ref. [78] and references therein). It was found that inner sphere adsorption (shown in Fig. 5.14, right), with -161.6 and -113.6 kJ moF for the anionic and zwittetionic species, respectively is significantly more stable as compared to outer sphere adsorption (-20.5 kJ mol (Fig. 5.14, left)). Beyond the result itself, it is important to note that complex events can now he handled with ab initio methods because they are able to model aU types of forces in reasonable agreement with experiment. 

Another interesting surface reaction involves the direct synthesis of a metal-coordinated porphyrin array. From the perspective of surface science, surlace-supported 2-D metal-oiganic frameworks (MOFs) with open-spaced adlayers have been extensively investigated under UHV on a variety of metal single crystal surfaces, such as Au, Ag, and Cu [16-18]. The 2-D stmctures of these MOFs, including, for example, the 2-D supramolecular coordination of not only zinc(II) telrapyridyl porphyrin (ZnTPyP) with Au [17] but also the bicomponents composed of ZnTPyP and 4, 4""-(l,4-phenylene)bis(2,2 6, 2"-terpyridine)... 

PTPy) with Fe [18], have been characterized by STM. Surfece-supported metal-organic MOFs are often nsed as host frameworks for small organic molecules, such as fiillerene [5,16], Oiganometalhc 2-D nanosheets were formed on Au(lll) by the reaction of telra-cyanobenzene with Fe at elevated tanperatures under UHV [19], Thus, the choice of coordination metal makes it possible to precisely control these kinds of nanostructure. 

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