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 electron‐acceptor (-NO2) groups or electron‐donor (-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.