Tuning and Directing Energy Transfer in the Whole Visible Spectrum through Linker Installation

While limited choice of emissive organic linkers with systematic emission tunability presents a great challenge to investigate energy transfer (ET) over the whole visible light range with designable directions, luminescent metal-organic frameworks (LMOFs) may serve as an ideal platform for such study due to their readily tunable structure and composition. Herein, five Zr 6 cluster-based LMOFs, HIAM-400X (X = 0, 1, 2, 3, 4) are prepared using 2,1,3-benzothiadiazole and its derivative-based tetratopic carboxylic acids as organic linkers. Their emission energies range from ~470 to 645 nm. The accessible unsaturated metal sites confer HIAM-400X as a pristine scaffold for postsynthetic modification via linker installation. Six 2,1,3-benzothiadiazole and its derivative-based dicarboxylic acids (L) with their emission energies covering the entire visible spectrum were successfully installed into HIAM-400X matrix to form thirty HIAM-400X-L LMOFs, in which the energy transfer can be facilely tuned by controlling its direction, either from the inserted linkers to pristine MOFs or from the pristine MOFs to inserted linkers, and over the whole range of visible light. The combination of the pristine MOFs and the second linkers via linker installation creates a powerful two-dimensional space in tuning the emission via energy transfer in LMOFs. This work sheds light on a new strategy in designing target-specific materials for light-harvesting, energy transfer and related applications.