Design and construction of porphyrin box-based metal–organic frameworks with hierarchical superstructures for efficient energy transfer and photooxidation

Abstract

The design and construction of MOFs containing separate porphyrin boxes (PBs) with large cavities and hierarchical superstructures are of great significance for their photochemical applications and host–guest chemistry, yet they still present significant challenges. Herein, we demonstrate the rational design and assembly of a PB-based MOF with hierarchical superstructures (QPF-2), built with 4-connected Zn ions and a flexible porphyrin ligand, tetrakis(3-carboxyphenyl)porphyrin (3-TCPP). Single crystal X-ray analysis revealed that 4-connected Zn₂ nodes and “table” conformers of 3-TCPP ligands contribute to the assembly of PBs with hollow cavities, which are further connected by “chair” conformers of 3-TCPP linkers to form the three-dimensional superstructure with a new topological network. The inner cavities and outer pores of PBs in QPF-2 contribute to a total solvent accessible volume of 63.9%. By virtue of its efficient energy transfer and hierarchical superstructures, QPF-2 efficiently catalyzes the photooxidation of 1,5-dihydroxynaphthalene derivatives compared to other Zn-porphyrin-based MOFs. This work contributes to the crystal structure engineering in porphyrinic MOFs and may provide a new avenue for the development of PB-based photocatalysts.