Structural Modulation of Porphyrin-Based Supramolecular Prisms for Efficient and Selective Photocatalysis

Porphyrin and its derivatives have been widely used as photocatalytic units owing to their strong absorption in the visible region. However, their extended π-conjugated systems will lead to aggregation and reduce the photocatalytic efficiency. In this work, we report the construction of supramolecular prisms S1 and S2 with porphyrin motifs by assembling terpyridine-based ligands and Zn²⁺. These supramolecules were characterized by NMR, ESI-MS, TWIM-MS, and single-crystal X-ray diffraction. By rational molecular design, supramolecular prisms effectively attenuate the stacking of the photosensitive porphyrin motifs, thus further improving the reaction efficiency of the selective photocatalytic oxidation of sulfide to sulfoxide. Compared with S1 with close distance between porphyrin motifs, S2 with increasing distance of porphyrins was able to completely convert sulfide ether to sulfoxide within 25 min, without the formation of any byproducts. The enlarged porphyrin distance in S2 significantly enhanced the photocatalytic efficiency by suppressing π-π stacking and promoting exciton separation and charge-carrier mobility. The catalytic mechanism reveals that the unique supramolecular structural design played the key role in the photocatalytic process. This work highlights that the catalytic performance of supramolecular prisms can be effectively tuned by reducing the close packing of functional motifs to enable efficient chemical transformations.