Single crystalline, Non‐stoichiometric Hydrogen‐bonded Organic Frameworks Showing Versatile Fluorescence Depending on Composition Ratios and Distributions

We report on the synthesis, characterization and photobehavior of single crystalline non‐stoichiometric hydrogen‐bonded organic frameworks (NS‐HOFs). NS‐HOFs (BTNT‐1) with various composition ratios were successfully obtained as single crystals from two analogue tetratopic carboxylic acids, possessing naphthalene and benzothiadiazole cores NTTA and BTTA, respectively. The heterogeneous distribution of the components was thoroughly confirmed by time‐resolved fluorescence microscopy and focused synchrotron X‐ray radiation techniques, for the first time. The versatile fluorescence of BTNT‐1 behavior depends on the composition ratio and distribution of the component in the single crystals. We observed not only fluorescence bands with various colors such as purple, blue, green and white, depending on the composition ratio of both components in BTNT‐1, but also different emission bands from a single crystal. Furthermore, we provide details on their emission lifetimes following the composition, emission color and targeted region on the crystal. These results demonstrate unique and versatile optical properties of carboxylic acid‐based NS‐HOFs and provide a concept of creating functional mixed porous materials capable of different and tunable optical properties.