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48 Chapter 3<br />
3.1.6 Summary<br />
Applying CSA, a series of Ru-MOFs [Ru3(BTC)2Yy]n·G g were synthesized under<br />
solvothermal conditions and fully characterized(Table 3.4). Varying the R-group and<br />
nature of the counter-ion in the Ru-SBU ([Ru2(OOCR)4X] and [Ru2(OOCCH3)4]A), tuning<br />
(up to a certain extent) the local environment of the metal sites while retaining the same<br />
structure were achieved. Changing the R-group at the carboxylate in the Ru-SBU from -<br />
CH3 to bulkier –Rs, for example -C(CH3)3, leads to a striking improvement of the<br />
crystallinity of the final MOFs. However, considering the MOF compositions, the whole<br />
picture gets complicated, as residual guest molecules/species G could stem from both<br />
different R-groups in the Ru-SBU ([Ru2(OOCR)4X]) and solvents (including used<br />
carboxylic acids).<br />
Table 3.4. Summary of the preparation, composition and S BET in [Ru 3 (BTC) 2 Y y ] n·G g (1-4_ex). BTC<br />
= 1,3,5-benzenetricarboxylate, H 3 BTC = 1,3,5-benzenetricarboxylic acid, AcO = acetate, AcOH =<br />
acetic acid, PivOH =pivalic acid.<br />
sample<br />
employed SBUs for synthesis<br />
Counter-ions<br />
Y<br />
guest<br />
molecule G<br />
S BET<br />
(m 2 /mmol)<br />
1_ex<br />
SBU-a<br />
[Ru 2 (OOCCH 3 ) 4 Cl] n<br />
Cl, AcO<br />
1.5AcOH,<br />
0.1H 3 BTC,<br />
4H 2 O<br />
963<br />
2_ex<br />
SBU-b<br />
[Ru 2 (OOCC(CH 3 ) 3 ) 4 (H 2 O)Cl](CH 3 OH)<br />
Cl, OH<br />
2.4AcOH,<br />
0.15H 3 BTC,<br />
0.45PivOH<br />
718<br />
3_ex<br />
SBU-c<br />
[Ru 2 (OOCCH 3 ) 4 (THF) 2 ](BF 4 )<br />
F, OH<br />
2.4AcOH,<br />
0.5H 3 BTC,<br />
3H 2 O<br />
850<br />
4_ex<br />
SBU-d<br />
[Ru 2 (OOCCH 3 ) 4 (H 2 O) 2 ](BPh 4 )<br />
OH<br />
1.4AcOH,<br />
0.8H 3 BTC,<br />
3H 2 O<br />
941<br />
Besides this, the counter-ion Cl - is still present to compensate the charge of the [Ru2] 5+ PW<br />
units. Therefore, keeping the same R-group (-CH3) in the Ru-SBU, the Cl - counter-ions<br />
were replaced by WCAs. As expected, the ruthenium centers were modified through<br />
introducing more weakly coordinating anions. The more coordinatively active the<br />
counter-ions in the Ru-SBU are, the easier they coordinate to the metal centers in the final<br />
MOF structure. In spite of the fact, that BF4 was absent in the structure of 3_ex, F - was<br />
found in the material by EDX and EA. Therefore, Ru-SBUs with more stable WCA, like BPh4,
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