Retention of Intrinsic Photophysical Properties of Porphyrin Building Blocks in 3D Organic Frameworks through Magic...

Construction of three-dimensional (3D) frameworks maintaining intrinsic photophysical properties of monomeric building blocks is difficult and challenging due to the existence of various molecular interactions, such as metal-organic and π-π interactions. A 3D hydrogen-bonded organic framework (YSH-1_Zn) with permanent porosity was constructed using a porphyrin having six carboxylic acid groups (1_Zn). Brunauer-Emmett-Teller surface area measurement indicated that YSH-1_Zn has a porous structure with a surface area of 392 m²/g. Single-crystal X-ray diffraction analysis revealed that 1_Zn creates a 5-fold interwoven 3D network structure adopting a monoclinic system with a space group of P21/c. Each 1_Zn within a single crystal exhibits parallel alignment with a slip-stack angle of 54.6°, in good agreement with the magic angle. Although the center-to-center distance of the nearest zinc atoms in YSH-1_Zn is only 5.181 Å, the UV/vis absorption and fluorescence emission of YSH-1_Zn are not different from those of 1_Zn, indicating the absence of an interaction between excitons. Due to the magic angle alignment of 1_Zn, the fluorescence lifetime, decay profiles, and quantum yield remained uniform even in the solid state.