“…After the addition of DCN, the fluorescence lifetime of 1 was almost not affected, confirming that the quenching does not result from interactions between DCN and the skeleton (Figure S11). ,, Meanwhile, according to density functional theory (DFT) simulations, the H 4 BDPO ligand has a lower energy level of lower unoccupied molecular orbitals (LUMO) relative to DCN (Figure a and Table S4), which hinders the charge transfer of electrons from H 4 BDPO to DCN, implying that a photoinduced electron transfer (PET) process is not the reason for fluorescence quenching here. , According to the above discussion and previous literature reports, ,, the quenching mechanism may be largely attributed to resonance energy transfer (RET). The process is mainly through effective overlaps between the emission band of the MOF and the the absorption band of the analyte, so that the resonance energy shifts to the analyte, thus resulting in fluorescence quenching.…”