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104 Chapter 4
reactive metal centers, thus, affecting the catalytic activity of the 1b-d samples. On the
other hand, Ru-DEMOF 2a displays higher yield of pyrrole compared to the parent Ru-
MOF (82% vs. 48%), regardless of the partial absence of the metal centers (defects B)
(Figure 4.39). This could be a result of the smaller steric hindrance surrounding the Ru-
CUSs while employing the H2ip DL. When the contents of the incorporated DLs are rather
small (i.e., as in 2a), the negative influence caused by missing metal centers is relatively
insignificant compared with the positive effect of the smaller steric hindrance. Therefore,
2a Ru-MOF material shows as high catalytic activity in present reaction as 1a. Similar
observations have been found for the samples 1b-c because of the somewhat larger steric
hindrance of OH-groups in spite of the type A defect in these materials. To note, using
IRMOF-3 as catalysts in the same reaction, 96% conversion after 60 min was achieved.
However, this could be attributed to the higher regent ratio (aniline: 2,5-hexanedione =
1:1.7). [245] Nevertheless, the current study using Ru-DEMOFs as catalysts give us insight
into the influence of catalytic activity caused by different defect types. For further
investigation, it would also be interesting to optimize the catalytic activity by improving
the regent ratio.
Figure 4.38. Time-yield plot of Paal-Knorr synthesis of aniline reacting with 2,5-hexadione, giving
the pyrrole employing Ru-DEMOFs 1a-1d (with 8%, 20%, 32% and 37% 5-OH-ip incorporation,
respectively) as catalysts in comparison with the parent Ru-MOF(parent). Blank stands for the
experiment where no catalyst was added into the reaction mixture.