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120 Chapter 4
Figure 4.50. From left to right: UHV-IR spectra of the parent Cu-BTC and Cu-DEMOFs D1 (20% of
ip) and D2 (25% of ip) upon CO dosing (p(CO): 1×10 -6 - 3×10 -4 mbar) collected at 92-98 K after
annealing at 480 K. The low intensity absorption bands at 2127 cm -1 in the parent Cu-BTC indicate
some inherent defects that cannot be avoided during the crystal formation. Figure has been
provided by M. Kauer.
As illustrated in Figure 4.5, two representative types of defects are expected in the
formation of DEMOFs. The generation of defect type A (i.e. modified PWs with the creation
of the reduced Cu-sites) can be also expected in the solids D1 and D2 due to the utilization
of reducing agents (DMF). Although Cu + related CO bands (2127 cm -1 ) appear in parent
HKUST-1, the relative intensity to Cu 2+ related CO bands (2178 cm -1 ) is lower. However,
in both D1 and D2 the CO bands at 2120 cm -1 attributed to Cu + -CO interaction turn to be
dominant in comparison with the bands at 2178 cm -1 . Thus it gives us a hint that presence
of defect type A can be one of the possibilities. Notably, intensity of both Cu 2+ - (2178 cm -
1 ) and Cu + -related bands (2120cm -1 ) decreases from D1 (20% ip) to D2 (25%). The
similar scenario has been also found for the 5-OH-ip incorporated Ru-DEMOF samples
described in Chapter 4.2, suggesting thus simultaneous formation of defects B upon higher
doping of DL, namely missing Cu-PWs. Consequently, lower abundance of Cu 2+ and Cu +
metal centers in the D2 frameworks expected, explaining observed changes of the
decreased intensity of the bands related to Cu 2+ and Cu + . Cu-DEMOFs with ip (obtained
also from Cu(NO3)2·3H2O) reported earlier by Hupp et al. suggest generation of only
defects type B by simulation of defects. Thus, it might be possible that anions of the
utilized metal precursors play an important role on intentional defects formation in Cu-