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Chapter 3 45<br />
m 2 /mmol (based on the N2 isotherm) and does not differ much in contrast to the sample<br />
before “solvent exchange” (i.e. sample 2). Notably, the thermal stability of 2_ex also<br />
slightly decreased after solvent exchange like SBET. Hence, the overall quality of this Ru-<br />
MOF analog is less convincing under the circumstances of this study. Interestingly, in case<br />
of 3_ex, however, an increase of the SBET has been observed from the N2 sorption<br />
isotherms (850 vs. 683 m 2 /mmol) (Table 3.3). The same increase of SBET has also been<br />
observed for the sample 4_ex (941 m 2 /mmol) in comparison with the value before (916<br />
m 2 /mmol), where the residual [BPh4] - has been removed via solvent exchange procedure<br />
although the amount of acetic acid does not differ. Thus, in particular for Ru-MOFs 1 and<br />
3, solvent exchange procedure proved to be a good method to reduce the amount of<br />
residual acid molecules. In both cases the thermal stability, crystallinity and porosity were<br />
preserved. For the material 4, solvent exchange is helpful to wash out the residual [BPh4] -<br />
counter anions to give access to the metal-sites, while keeping the thermal stability and<br />
porosity.<br />
Table 3.3. Comparison of the BET surface area (S BET ) of the Ru-MOFs before (1-4) and after<br />
solvent exchange (1-4_ex) in the unit of m 2 /g and m 2 /mmol. S BET in the unit of m 2 /mmol is<br />
calculated by S BET (m 2 /g) and the corresponding molecular weight (M w ) determined from both EA<br />
and 1 H NMR results. M w of 1-4_ex is obtained from the formula given in Table 3.2. The M w of<br />
sample 1-4 is derived from the difference of the guest molecules between the samples before and<br />
after solvent exchange, namely: M w (1) = M w (1_ex + 3.2 AcOH); M w (2) = M w (2_ex + 0.6 AcOH +<br />
0.2 PivOH); M w (3) = M w (3_ex + 1.4 AcOH); M w (4) = M w (4_ex + 0.13 BPh 4 ).<br />
samples S BET (m 2 /g) S BET (m 2 /mmol)<br />
1 958 1108<br />
1_ex 998 964<br />
2 851 888<br />
2_ex 728 718<br />
3 604 683<br />
3_ex 812 850<br />
4 840 916<br />
4_ex 897 941<br />
[Cu 3 (BTC) 2 ] n<br />
* theoretical accessible surface area.<br />
1734 [83]<br />
2153* [205]<br />
1049<br />
1301
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