Resolving Dye Embedment in MOF‐5: Multimodal Evidence for Perylene‐Based Guest Encapsulation

Abstract The interplay between two single components within a hybrid system plays a particular role for the formation of new functional materials with specific properties. In this respect, photoactive metal‐organic frameworks (MOFs) with a non‐covalently bonded incorporated photochromic or luminescent guest are intensively studied due to the beneficial contribution of the MOF scaffold on the switching properties and luminescence brightness. However, a crucial point remains the unambiguous proof of dye embedment as non‐covalently attached guest molecule versus dye adsorption on the MOF surface, which cannot be resolved utilizing one specific analysis method. This work illustrates the powerful combination of Powder X‐ray diffraction (PXRD), infrared (IR) spectroscopy and N 2 physisorption measurements with advanced photoluminescence studies (steady–state and time‐resolved) to monitor the explicit incorporation of perylene derivatives into porous MOF‐5. These experimental findings are supported by DFTB3 molecular dynamics (MD) simulations, which show that dyes preferentially occupy large pores, form stable dimers or oligomers, and interact mainly with the MOF's organic linkers.