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Intensity, a. u.<br />
Chapter 3 35<br />
3.1.3.3 Acid digestion and composition of the obtained Ru-MOFs 1-4<br />
4_ex<br />
4<br />
3_ex<br />
H(BTC)<br />
H(BPh 4<br />
)<br />
H(AcO)<br />
3<br />
2_ex<br />
H(PivO)<br />
2<br />
1_ex<br />
1<br />
10 8 6 4 2 0<br />
, ppm<br />
Figure 3.6. NMR spectra (measured in DCl/DMSO-d 6 ) of the Ru-MOF samples before (1-4) and<br />
after solvent exchange (1-4_ex) . All spectra were normalized by dividing the intensity of H(BTC),<br />
respectively. PivO = pivalate, AcO = acetate. Due to the sensitivity of water peak to the solution<br />
conditions, the proton resonance of H 3 O + varies here in the range of 4-6 ppm, dependent on the<br />
concentration of DCl in the total solution.<br />
To get more insight into the microstructures (i.e. analytical purity) and composition of the<br />
materials 1-4, 1 H-NMR analysis of the acid-digested (in DMSO-d6/DCl mixture) Ru-MOF<br />
samples was performed. Thus, the 1 H-NMR spectra revealed, that besides the signals at δ<br />
= 8.61 ppm attributed to the aromatic protons of BTC, one additional resonance at δ = 1.88<br />
ppm is seen and can be assigned to the protons of the residual acetic acid (AcOH) for all<br />
four Ru-MOFs samples (Figure 3.6). For Ru-MOF 2, the spectrum shows also an additional<br />
signal at δ = 1.05 ppm, which corresponds to the protons of the residual pivalic acid<br />
(PivOH) (Figure 3.7). The spectra suggest that the larger R-group (-C(CH3)3 instead of -<br />
CH3) in the Ru-SBU leads to more impurity in the synthesis of MOFs in addition to the
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