Fluorescence Quenching Pathway
Frontier molecular orbital (FMO) analysis of host-guest systems showed
that of electron density distribution changes upon the incorporation of
an analyte with electronâacceptor (-NO2) groups or
electronâdonor (-CH3) groups, see Figure 3. The FMOs of
Zn-MOF-toluene and Zn-MOF indicate that both systems exhibit similar
features, as the HOMO in both systems exhibits that electron density is
distributed on the OBA linkers while the LUMO is located on BPY linkers.
In case of Zn-MOF-toluene, the molecular orbitals located on the guest
molecule appear in a set of inner occupied molecular orbitals, as well
as more external molecular orbital into the virtual space, see Figure S1
Supporting Information. However, when the guest is the NACs such as
nitrobenzene, the HOMO is totally distributed on the OBA linkers whereas
the LUMO is extended on the nitrobenzene framework, see Figure 3. These
results are consistent with the reported by Ce Chao et
al.24 in regarding the analysis of the FMOs
considering the interaction between Zn-MOF and analyte.