Multi‐Emission from Single Metal–Organic Frameworks under Single Excitation

Multi‐emission materials have come to prominent attention ascribed to their extended applications other than single‐emission ones. General and robust design strategies of a single matrix with multi‐emission under single excitation are urgently required. Metal–organic frameworks (MOFs) are porous materials prepared with organic ligands and metal nodes. The variety of metal nodes and ligands makes MOFs with great superiority as multi‐emission matrices. Guest species encapsulated into the channels or pores of MOFs are the additional emission sites for multi‐emission. In this review, multi‐emission MOFs according to the different excitation sites are summarized and classified. The emission mechanisms are discussed, such as antenna effect, excited‐state intramolecular proton transfer (ESIPT) and tautomerism for dual‐emission. The factors that affect the emissions are revealed, including ligand–metal energy transfer and host–guest interaction, etc. Multi‐emission MOFs could be predictably designed and prepared, once the emissive factors are controlled rationally in combination with the different multi‐emission mechanisms. Correspondingly, new and practical applications are realized, including but not limited to ratiometric/multi‐target sensing and bioimaging, white light–emitting diodes, and anti‐counterfeiting. The design strategies of multi‐emission MOFs and their extensive applications are reviewed. The results will shed light on other multi‐emission systems to develop the structure‐derived functionality and applications. The variety of metal nodes, ligands, and guest molecules provide the potential emission centers to endow metal–organic frameworks (MOFs) with great potential as a multi‐emission matrix. In this review, the multi‐emission MOFs excited under a single wavelength are summarized and classified according to the different excitation sites. Furthermore, the design concept, and application of multi‐emission MOFs are summarized.