The modulation effect of an electron-rich guest on the luminescence of naphthalene diimide-based metal–organic frameworks

Abstract

Host–guest systems based on donor–acceptor interactions have attracted considerable attention as a new platform for the preparation of luminescent metal–organic frameworks (MOFs). However, reasonable design and modulation of donor–acceptor interactions with charge transfer based fluorescence remains a challenge owing to the elaborate self-assembly process of acceptor and donor components. Taking into account the design principles of the host–guest system, a well-defined MOF with an electron-deficient nature should be an ideal host for the building of charge transfer based fluorescent materials. Herein, we have successfully fabricated a suite of host–guest materials (MOFs 2–8) exhibiting charge transfer based fluorescence by virtue of the interactions between electron-rich naphthalene derivatives and an electron-deficient naphthalene diimide-based MOF (MOF 1) as the donor and acceptor, respectively. Profiting from the clear naphthalene derivatives to electron-deficient MOF framework charge transfer interactions, these host–guest materials exhibit color-tunable emissions over a wide range by rational selection of naphthalene derivative molecules. Furthermore, electronic structure calculations reveal that the multicolor emissions of the newly synthesized MOFs depend on the HOMO energy level/ionization potential of naphthalene derivatives. This work provides a promising strategy for the assembly of various novel charge-transfer fluorescent materials as potential luminophores.